Methods using a robotic catheter system

[0001] The present application claims the benefit under 35 U.S.C. §119 to U.S. provisional patent application Ser. Nos. 60/600,869, filed Aug. 12, 2004, 60/644,505, filed Jan. 13, 2005, 60/677,580, filed May 3, 2005, and 60/678,097, filed May 4, 2005. The foregoing applications are hereby incorporated by reference into the present application in their entirety.

[0002] The invention relates generally to robotically controlled systems, such as telerobotic surgical systems, and more particularly to a robotic catheter system for performing minimally invasive diagnostic and therapeutic procedures.

[0003] Robotic surgical systems and devices are well suited for use in performing minimally invasive medical procedures, as opposed to conventional techniques wherein the patient's body cavity is open to permit the surgeon's hands access to internal organs. For example, there is a need for a highly controllable yet minimally sized system to facilitate imaging, diagnosis, and treatment of tissues which may lie deep within a patient, and which may be preferably accessed only via naturally-occurring pathways such as blood vessels or the gastrointestinal tract.

[0004] In accordance with a general aspect of the invention, methods are provided for using robotic catheter system to perform a procedure on a patient. In one embodiment, the method includes generating a control signal corresponding to movement of a master input device, and moving a plurality of drive elements of an instrument driver in response to the control signal, the drive elements operatively coupled to a corresponding plurality of control elements of an elongate guide instrument, the control elements secured to a distal end of the guide instrument and moveable axially relative to the guide instrument such that movement of the drive elements causes a corresponding movement of the guide instrument distal end.

[0005] The method may optionally further include generating a further control signal using the master input device, and moving one or more further drive elements of the instrument driver in response to the further control signal, the one or more further drive elements operatively coupled to a corresponding one or more control elements of an elongate sheath, the one or more control elements secured to a distal end of, and moveable axially relative to, the sheath, such that movement of the one or more further drive elements causes a corresponding movement of the sheath, the sheath comprising a lumen through which the guide instrument is coaxially disposed.

[0006] In one embodiment, the method further includes manipulating the master input device so as to cause the guide instrument to move axially relative to the sheath. In another embodiment, the method further includes manipulating the master input device so as to cause the respective guide instrument to rotate relative to the sheath. Optionally, an outer surface of the guide instrument and a surface defining the sheath lumen may be jointly configured to limit rotational movement of the guide instrument relative to the sheath.

[0007] In one embodiment, the control signal causes individual ones of the plurality of drive elements to move independently of one another in order to achieve a desired bending of the guide instrument distal end. A master input device may be operatively coupled to a controller that determines a tensioning to be applied by a respective drive element to a respective guide instrument control element based on a kinematic relationship between the desired bending and a linear movement of the guide instrument control element relative to the guide instrument.

[0008] In one embodiment, a working instrument is provided in a working lumen of the guide instrument. By way of non-limiting example, the working instrument may comprise an ablation catheter positioned such that an electrode located on the ablation catheter is sticking out of a distal end opening of the working lumen, wherein the method further includes using the master input device to position the guide instrument distal end in a heart chamber of the patient such that the electrode is contacting tissue in a surface of the heart chamber. By way of another non-limiting example, the working instrument may be a guidewire. By way of yet another non-limiting example, the working instrument may comprise a needle and dilator positioned such that the needle is protruding through a distal end opening of the working lumen, wherein the method further includes using the master input device to position the guide instrument distal end adjacent an atrial wall of the patient, move the guide instrument to cause the needle to puncture through the atrial wall, and move the guide instrument to cause the dilator to move through an opening in the atrial wall created by the needle puncture.

[0009] In one embodiment, the method includes displaying, proximate the master input device, acquired images of anatomy of the patient proximate the guide instrument distal end. The images may be acquired with an imaging system comprising an elongate imaging instrument configured for placement in a body passage or cavity of the patient and having an operative imaging element located on a distal portion thereof. The controller may determine a tensioning to be applied to a respective guide instrument control element based on data from the acquired images. By way of non-limiting examples, the images may be acquired by an ultrasound imaging system, an optical imaging system, a fluoroscopic imaging system, a computer tomography imaging system, or an MR imaging system.

[0010] In one embodiment, the method includes obtaining position information regarding the guide instrument from a localization system operatively coupled to the controller. For example, the controller may determine a tensioning to be applied to a respective guide instrument control element based on position data from the localization system. By way of non-limiting examples, the localization system may be selected from the group comprising an ultrasound localization system and an electromagnetic localization system.

[0011] In one embodiment, the method includes using the master input device to position an operative contact sensing element carried on the distal end of the guide instrument in contact with internal body tissue of the patient.

[0012] Other and further embodiments and aspects of the invention will become apparent upon review of the following detailed description in view of the illustrated embodiments.

[0175] Referring to FIG. 1, one embodiment of a robotic catheter system 32, includes an operator control station 2 located remotely from an operating table 22, to which a instrument driver 16 and instrument 18 are coupled by a instrument driver mounting brace 20. A communication link 14 transfers signals between the operator control station 2 and instrument driver 16. The instrument driver mounting brace 20 of the depicted embodiment is a relatively simple, arcuate-shaped structural member configured to position the instrument driver 16 above a patient (not shown) lying on the table 22.

[0176] In FIG. 2, another embodiment of a robotic catheter system is depicted, wherein the arcuate-shaped member 20 is replaced by a movable support-arm assembly 26. The support assembly 26 is configured to movably support the instrument driver 16 above the operating table 22 in order to position the instrument driver 16 for convenient access into desired locations relative to a patient (not shown). The support assembly 26 in FIG. 2 is also configured to lock the instrument driver 16 into position once it is positioned.

[0177] Referring to FIG. 2.1, a view of another variation of an operator control station (2) is depicted having three displays (4), a touchscreen user interface (5), and a control button console (8). The master input device (12) depicted in the embodiment of FIG. 2.1 is depicted and described in further detail in reference to FIG. 105B. Also depicted in the embodiment of FIG. 2.1 is a device disabling switch (7) configured to disable activity of the instrument temporarily. The cart (9) depicted in FIG. 2.1 is configured for easy movability within the operating room or catheter lab, one advantage of which is location of the operator control station (2) away from radiation sources, thereby decreasing radiation dosage to the operator. FIG. 2.2 depicts a reverse view of the embodiment depicted in FIG. 2.1.

[0178] FIG. 3 provides a closer view of the support assembly 26 depicted in the embodiment of FIG. 2. The support assembly 26 comprises a series of rigid links 36 coupled by electronically braked joints 34. The joints 34 allow motion of the links 36 when energized by a control system (not shown), but otherwise prevent motion of the links. The control system may be activated by a switch (e.g., a footswitch or thumbswitch), or computer interface. In another embodiment, the rigid links 36 may be coupled by mechanically lockable joints, which may be locked and unlocked manually using, for example, locking pins, screws, or clamps. The rigid links 36 preferably comprise a light but strong material, such as high-gage aluminum, shaped to withstand the stresses and strains associated with precisely maintaining a three-dimensional position of the approximately ten pound weight of a typical embodiment of the instrument driver 16 once the position of the link 36 is fixed.

[0179] FIGS. 3.1-3.10B depict another embodiment of the support assembly, also designated by reference no. 26. Referring to FIGS. 3.1 and 3.2, in this embodiment, a mechanical operating table interface 1 includes a pair of clamp members 89 to removably attach the support assembly 26 to the operating table 22 (shown in phantom outline). As explained in greater detail in conjunction with FIG. 3.3, the clamp members 89 include a lower clamp toe configured to pivot outwards for ease in engaging a rail (not shown) on an edge of the operating table 22.

[0180] The main body of the mechanical interface 1 is fixed to the housing of a solenoid and brake unit 3. A proximal base of an arcuate, vertical extension member 11 is coupled to, and selectively rotable about a central axis of, the solenoid and brake unit 3. The vertical extension member 11 bends through an angle of approximately 90°, and has a distal end rotatably coupled, via a pan-rotate interface 13, to a first end of a further extension member 15. As explained in greater detail in conjunction with FIG. 3.6, the pan-rotate interface 13 selectively allows extension member 15 to both rotate about an axis of a distal extending shaft 55 (seen in FIG. 3.2), as well as pan laterally along an arc defined by lateral movement of the shaft 55 through a pan slot 111 defined by the housing 121 of the pan-rotate interface 13 in a plane that is preferably parallel to a plane defined by the operating table.

[0181] A distal brake unit 19 is coupled to a sprocket comprising the second end of extension member 15, the sprocket being rotatably coupled to the housing of the extension member 15, as described in further detail below. The brake unit 19 is configured for selectively allowing rotation of an instrument driver support shaft 17 relative to the brake unit 19, the support shaft 17 carrying a pivotable mounting interface 21 for attaching the instrument driver (not shown). The support shaft 17 further includes a handle portion 23, which has a button 24 for electronically actuating the respective electronic brake and solenoid in unit 3, as well as the distal brake 19, to thereby allow the afore-described motions of the various components of the assembly 26. Cable holder brackets 113 are provided along the exterior of the support shaft 17, pan-rotate interface 13, and solenoid and brake unit 3, respectively, for attaching a power/control cable from the instrument driver (not shown). One a more control cables (not seen) also extend internally within the various components of the assembly 26 from the distal end button 24 to the distal brake 19 and to the solenoid and brake unit 3.

[0182] The support assembly 26 is configured to facilitate easy positioning and repositioning of a remotely controlled instrument driver over the operating table 22. When the button 24 on the handle portion 23 is depressed, the respective electronic brakes and solenoid of the assembly 26 allow the respective interfaces to move freely relative to each other, constrained only by the interface configurations, to allow for repositioning of the handle 23 and associated instrument driver support shaft 17 relative to the operating table 22. When the button 24 is not depressed, the respective brakes prevent any further movement of the support shaft 17, wherein the support assembly 26 is configured to provide a high level of mechanical stability. In one embodiment, upon activation of the solenoid and release of the brakes, the distal brake unit 19 is configured to allow an approximately 135 degree range of motion about the rotation axis 125 of the brake unit 19, the pan-rotate interface 13 is configured to allow an approximately 140 degree range of motion rotation about the rotational axis of the shaft 55 as well as approximately 110 degrees of pan rotational motion through the plane defined by the pan slot 111, and the vertical extension member 11 is configured to allow an approximately 350 degree range of rotational motion relative to the solenoid and brake unit 3, which is configured to be coupled to an operating table.

[0183] As shown in FIG. 3.3, the mounting clamps 89 each generally comprise a fixed body portion 33 having a mating surface 101, and upper and lower clamp toe portions 115 and 99, configured for attachably coupling to a rail (not shown) disposed on an edge of the operating table 22. The lower clamp toe portion 99 is preferably fastened to the swinging clamp body portion 29, with a threaded locking member 25 used to tighten/loosen the lower clamp toe portion 99 against the rail to secure/release the clamp 89 thereto or therefrom. For ease in loading the assembly 26 onto an operating table rail, the mating surface 101 of the fixed clamp body portion 33 is indented to seat a fulcrum rod 27 that rides against a side of the rail, and the swinging clamp body portions 29 of the clamps 89 may be individually pivoted (95) about the pin member 31 to rotate away from the operating table rail (not shown) to facilitate extending the upper clamp toe member 115 onto the rail with easy access to the mating surface 101. In the depicted embodiment, the swinging clamp toe bodies 29 are spring 97 biased to rotate (95) in this manner until the mating surface 101 has been positioned against the operating table rail (not shown), subsequent to which the swinging clamp toe bodies 29 may be manually rotated about the pin 31 and wound into position interfacing with the operating table rail (not shown) with the threaded locking member 25, as depicted in FIG. 3.3.

[0184] Referring to FIG. 3.4, the solenoid and brake unit 3 comprises an outer housing 103 and an inner member 45 that is rotatably mounted within the housing 103. The inner member includes a distal facing surface 117, configured to receive a proximal mounting interface 94 of the vertical extension member 11 (See FIG. 3.2). In this manner, the extension member 11 (See FIG. 3.2) is rotatable about a longitudinal axis 119 of the solenoid and brake unit 3. A brake assembly 39 is biased to prevent rotation of member 45 (and, thus, of extension arm 11), unless electronically actuated to release the member 45. In FIG. 3.5, the brake 39 is depicted, along with a flex-disk interface 49 and a clamp 47, which couples firmly to the rotatable frame member 45. The flex-disk interface 49 allows for some axial movement between the clamp 47 and the brake 39, without significant rotational “slop” commonly associated with more conventional spline interfaces. Thus, manual rotation of the vertical arm 11 about an axis which may be substantially orthogonal to the operating table 22 (i.e., for positioning an instrument driver 16 mounted on the support shaft 17 relative to a patient positioned on the operating table 22) is selectively allowed by electronic activation of the brake 39 when the button 24 is depressed into the handle 23.

[0185] Referring back to FIG. 3.4, a top end of the unit 3 includes a plunger 41, that is biased by a set of helical springs 43 to push away from the housing 103 of the solenoid and brake unit 3, into an interior bore of the extension member 11. When a solenoid 35 located in a lower portion of the housing 103 is electronically activated, it pulls a pull-rod 37, which in turn pulls the plunger 41, in a compressive direction against the springs 43, toward the housing 103 of the solenoid and brake unit 3.

[0186] As shown in FIG. 3.6, the vertical extension member 11 has a hollow interior to accommodate an arcuate lever 57 configured to compress and lock into place the pan-rotate interface 13 when rotated counterclockwise about a pivot pin 61 within, and relative to, the vertical extension member 11 as the plunger 41 (see FIG. 3.4) is pushed upward away from the housing 103 (see FIG. 3.4) by the spring 43 load. With the plunger 41 pushed upward, the ball 53 is placed into compression between the toe 130 of the arcuate lever 57 and a contoured surface 131 coupled to the base of the pan-rotate interface 13 housing 121. The ball 53, contoured surface 131 and bearings 63 mounted upon the shaft 55 preferably are configured to place substantially all of the applied compressive load upon the ball 53 and not the bearings 63. When the plunger 41 is pulled downward by the activated solenoid 35, the load previously applied by the plunger 41 to the wheelset 59 at the end of the arcuate lever 57 is released and gravity pulls the arcuate lever 57 into clockwise rotation about the pivot pin 61, thus substantially releasing the compressive loads that lock into the place the pan-rotate interface 13 and allowing panning and rotation of the shaft 55. The pan-rotate interface 13 includes a ball 53 and shaft 55 construct (collectively indicated with ref no. as 51), that, in one embodiment, is configured to provide a 15:1 leverage ratio for loads applied by the plunger 41 at a wheel set 59 housed in the extension member 11 and coupled to the proximal end of the arcuate lever 57.

[0187] Referring to FIG. 3.7, the ball/shaft interface 51 comprises bearings 63 to facilitate stable panning rotation, as well as rotation of an associated structure about the longitudinal axis of the shaft 55. The ball 53 preferably is greased to facilitate smooth panning and rotation when not compressibly locked into position. The bearings facilitate lateral panning of the shaft member 55 about a plane formed by the pan-rotate interface 13, which causes the bearings 63 to rotate on a planar annulus about the center of the ball 53. The result is constrained motion in two different degrees of freedom: lateral panning as per the planar annulus and bearing interface, and rotation about the axis of the shaft 55. The bias force of the springs 43 on the plunger 41 extending from the solenoid housing 103 normally lock the ball/shaft interface 51 into place, preventing either panning or rotation motion at the interface. Electronic activation of the solenoid withdraws the pull-rod and, by extension, piston 41 away from the wheel set 59, thereby unloading the significant compressive forces that otherwise keep the ball 53 locked into place, allowing for panning/rotation.

[0188] Referring also back to FIG. 3.2, the shaft 55 protrudes through a horizontal slot 111 located in a distal face 123 of the housing 121 covering the pan interface 13. The slot 111 constrains the horizontal panning motion of the shaft 55 (and, by extension, the support member 15) in a plane that may be substantially parallel to the operating table within the range of motion defined by the boundaries of the slot 111.

[0189] Referring to FIG. 3.8, the shaft 55 is coupled to a proximal sprocket 75 of the horizontal extension member 15 using a conventional interference fit, such as a “number 3 Morse taper.” The proximal sprocket 75 is coupled to a distal sprocket 74 by a timing chain 73, so that rotation of the shaft 55 correspondingly rotates both sprockets 74 and 75, preferably with a 1:1 ratio of rotational movement, resulting in the same rotational displacement at each of the sprockets. Rotational movement of the proximal sprocket 75, caused by fixing the relative rotational position of the proximal sprocket 75 relative to the distal face 123 of the pan rotate interface 13 housing 121 with a key member 105 fitted into key slots (77, 109) defined by the distal sprocket 75 and pan rotate interface 13 housing 121, causes rotation of a pin 65, which in turn causes tension via a linkage 67, proximal linkage base 71, and distal linkage base 69, respectively, to a set of gas tension springs 79 configured to constrain the rotational motion of the sprockets 74 and 75 (and, thus, of the shaft 55). The position (107) of the key member 105 is depicted in FIG. 3.2. Given this configuration, with the solenoid 35 activated and the pan rotate interface 13 free to move, the timing chain 73 and sprocket 74/75 configuration within the horizontal extension member 15 is configured to maintain the relative planar positioning of the most distal hardware of the system relative to the plane of the operating table. This is important because a robotic catheter driver (not shown; see FIGS. 3.10A and 3.10B, for example) may be mounted upon the instrument driver interface 21 and pulled around by the handle 23, with the solenoid activated and the brakes released, to rotate about the rotational axis 125 of the distal brake unit 19, to rotate about the axis 119 of the rotatable frame member 45 within the solenoid and brake unit housing 3, to rotate and pan about the pan-rotate interface 13 via connectivity of the horizontal extension member 15, all simultaneously, without substantially changing the planar orientation of the instrument driver interface 21 relative to the plane of the operating table (not shown). In other words, the axis of rotation 125 of the proximal extension 127 of the instrument driver support shaft 17 may be configured to always be oriented perpendicular to the plane of the operating table, by virtue of the timing chain and sprocket interfacing of the extension member 15. When electronically activated, the brake 19 allows rotational movement of the of the support shaft 17 about an axis of the proximal extension 127. When the brake is not electronically activated, such rotational movement of the support shaft 17 is prevented.

[0190] Referring to FIGS. 3.9A and 3.9B, the instrument driver support shaft 17 comprises an instrument driver mounting interface 21, and a biasing spring 80 configured to at least partially counterbalance the cantilevered load upon the instrument driver interface 21 caused by the weight of an instrument driver mounted upon it. The biasing spring 80 preferably is covered by a spring housing 85. A lead screw 81 is provided and configured to change the pitch of the instrument driver interface 21 relative to the support shaft 17 when a knob 83 is rotated.

[0191] Referring to FIGS. 3.10A and 3.10B, an instrument driver fitted with a cover 129 is depicted mounted to the instrument driver interface 21. The cover 129 is configured to provide an additional barrier between the instrument driver which is covers and draping, liquids, vapors, and other substances that may be encountered during a procedure. Preferably the cover 129 comprises a polymer or metal material and is made with processes such as stereolithography, injection molding, or machining. Preferably the cover 129 may be snapped or fastened into place around the instrument driver with simple recessed screws, bolts, or other fasteners. Similar covers may be configured to cover instrument bases. As depicted in FIGS. 3.10A and 3.10B, the cantilevered mass of the covered instrument driver 129 creates a moment. Torsional loads associated with such moment are counteracted by the spring (not shown in FIGS. 3.10A and 3.10B—see FIG. 3.9A (80)) housed within the housing 85. This counteraction is configured to prevent binding of the knob 83 actuated lead screw 81 pitch control of the instrument driver interface 21.

[0192] In summary, a support assembly 26, or support structure, is configured to allow for easy repositioning of an instrument driver or other device relative to an operating table when an actuation button is depressed, thereby activating a solenoid and releasing two electronic brakes. The position of an instrument driver then may be easily fine-tuned, for example, or modified quickly and substantially to remove the instrument driver from the immediate area of a patient on an operating table for quick medical intervention with broad physical access. Constraints limit the movement of the instrument driver relative to the operating table—i.e., a pan-rotate interface 13, a horizontal extension member 15 with a rotational position maintaining timing chain 73 for distally-coupled structures, and brake-lockable rotations about two axes of rotation (125, 119) which may be parallel and both perpendicular relative to the plane of the operating table—to provide desirable mechanics. When an actuation button is not depressed and the structures are substantially locked into position relative to each other, with the exception of manually-activated lead screw pitch adjustment of an instrument driver interface 21, the support assembly 26 is configured to provide a robust structural platform upon which an instrument driver or other device may be positioned relative to an operating table.

[0193] FIGS. 4 and 5 depict isometric views of respective embodiments of instruments configured for use with an embodiment of the instrument driver (16), such as that depicted in FIGS. 1-3. FIG. 4 depicts an instrument (18) embodiment without an associated coaxial sheath coupled at its midsection. FIG. 5 depicts a set of two instruments (28), combining an embodiment like that of FIG. 4 with a coaxially coupled and independently controllable sheath instrument (30). To distinguish the non-sheath instrument (18) from the sheath instrument (30) in the context of this disclosure, the “non-sheath” instrument may also be termed the “guide” instrument (18).

[0194] Referring to FIG. 6, a set of instruments (28), such as those in FIG. 5, is depicted adjacent an instrument driver (16) to illustrate an exemplary mounting scheme. The sheath instrument (30) may be coupled to the depicted instrument driver (16) at a sheath instrument interface surface (38) having two mounting pins (42) and one interface socket (44) by sliding the sheath instrument base (46) over the pins (42). Similarly, and preferably simultaneously, the guide instrument (18) base (48) may be positioned upon the guide instrument interface surface (40) by aligning the two mounting pins (42) with alignment holes in the guide instrument base (48). As will be appreciated, further steps may be required to lock the instruments (18, 30) into place upon the instrument driver (16).

[0195] In one embodiment, the instruments (18, 30) are provided for a medical procedure in sterile packaging, while the instrument driver (16) is not necessarily sterile. In accordance with conventional sterile medical procedure, the nonsterile instrument driver (16) must be isolated from the patient by a sterile barrier of some type. Referring to FIGS. 7A-7C, a drape (50) comprising conventional surgical draping material may be folded into a configuration (52) to enable gloved hands of a person (not shown) to slide the drape (50) over the instrument driver (16), from one end to the other without contamination of the sterile side of the drape (50). The drape (50) is then unrolled around the instrument driver (16), as shown in FIGS. 7B and 7C.

[0196] Referring to FIGS. 8A and 8B, the interfacing between instrument driver (16) and instrument bases (46, 48) utilizing alignment pins (42) is depicted to further illustrate the issues associated with providing a sterile barrier between the instruments and driver. In the illustrated embodiment(s), wherein the instrument is a set of two instruments comprising both a sheath instrument (30) and a guide instrument (18), the draping is preferably configured to accommodate relative motion (56) between the two instrument bases (46, 48). Further, the fit between the instrument bases (46, 48) and pertinent alignment pins (42) preferably is not loose and does not allow for relative motion. Similarly, the interface between axels (54) extending from the instruments and sockets (44) comprising the instrument driver (16) preferably is a precision interface.

[0197] Referring to FIGS. 9-16, various embodiments of suitable draping schemas are depicted. As shown in FIG. 9, a perforated drape (58) may be utilized, wherein perforations (68) are sized to fit the alignment pins (42) and interface sockets (44). The perforated drape (58), preferably made from conventional draping materials, is simply aligned appropriately and pulled down upon the instrument driver (16).

[0198] Referring to FIG. 10, a perforated drape with socks (60) may also be utilized. The depicted drape (60) has perforations (68) for the underlying interface sockets (44), but has socks (70), also formed from conventional draping material, which are sized to encapsulate the mounting pins (42) of the instrument driver (16).

[0199] Referring to FIG. 11, the depicted drape (62) may comprise “socks” (70) to engage the mounting pins (42), as with the drape in FIG. 10, but also have integrated plastic sleeves (64) rotatably coupled to the surrounding conventional drape material. The integrated plastic sleeves (64) are preferably precisely sized to engage both the interface sockets (44) of the instrument driver (16) and the axels (not shown) of an instrument. The sleeves (64) are preferably constructed of a sterilizable, semi-rigid plastic material, such as polypropylene or polyethylene, which has a relatively low coefficient of friction as compared with conventional drape material. To decrease rotational friction between the integrated plastic sleeves (64) and the surrounding drape material, perforations in the drape material through which the sleeves (64) are to be placed may be circumferentially lined with plastic collars (not shown), comprising a material having a low coefficient of friction relative to that of the integrated plastic sleeves (64).

[0200] Referring to FIG. 12, an embodiment similar to that of FIG. 11 is depicted, with the exception that removable plastic sleeves (66) are not integrated into the drape, as delivered and unwrapped. Instead, the drape (60) may be delivered with perforations (68), circumferentially lined in one embodiment with plastic collars (not shown), positioned for convenient drop-in positioning of the sleeves (66). FIG. 13 is a close up view of a plastic sleeve (66) suitable, for example, in the embodiment of FIG. 12. The sleeve (66) may also be integrated into the embodiment depicted in FIG. 11. FIG. 14 illustrates that the inside of the sleeve (66) may be fitted to engage an axel (54) extending down from an instrument body.

[0201] Referring to FIG. 14.1, an alternative variation of a set of instruments (28) is depicted, wherein all of the parts with the exception of screws (91) and an axle (93) are comprised of polymeric materials such as polycarbonate or delrin. As depicted in FIG. 14.1, each axle (93) forms a spline interface with the associated control elements pulley which carries an associated tension element.

[0202] Referring to FIG. 15, another draping embodiment is depicted, wherein two semi-rigid covers or plates (72) are incorporated into a larger piece of conventional draping material. The covers (72) are configured to snap into position upon the sheath instrument interface surface (38) and guide instrument interface surface (40), fit over the mounting pins (42), and provide relatively high-tolerance access to the underlying interface sockets (44), with pre-drilled holes (76) fitted for the pertinent drive axel structures (not shown). Due to the anticipated relative motion between the two instrument interfaces, as previously described with reference to FIGS. 8A and 8B, it may be preferable to have elastic draping material or extra draping material bunched or bellowed in between the two interfaces, as shown in FIG. 15, and similarly applicable to the embodiments of FIGS. 9-14.

[0203] Referring to FIG. 16, another semi-rigid covering embodiment comprises a semi-rigid covering for the entire local surface of the instrument driver (16), without conventional draping in between semi-rigid sub-pieces. To accommodate relative motion, high tolerance overlap sections (78) are provided with sufficient overlap to allow relative motion without friction binding, as well as gapping of sufficient tightness that the sterility of the barrier remains intact. The semi-rigid covers of the embodiments of FIGS. 15 and 16 may be molded or machined from polymeric materials, such as polycarbonate, which are inexpensive, sterilizable, somewhat flexible for manual snap-on installation, and fairly translucent to facilitate installation and troubleshooting.

[0204] FIG. 17 is an isometric view of one embodiment of an instrument (18) configured for instrument steering via independent control of four catheter control elements, or four tension elements, such as cables comprising materials, e.g., stainless steel. The proximal portion (82) comprises a guide instrument base (48) and four axels (54) with associated manual adjustment knobs (86). The middle (84) and distal portions (87) comprise a catheter member which extends into the guide instrument base (48) forming part of the proximal portion (82).

[0205] Referring to FIG. 18, a catheter member (90) is depicted having control element apertures (92) through the proximal portion (88) of the catheter member to accommodate control elements (not shown), such as tension cables. The control elements may be disposed along the length of the catheter member (90), and positioned to exit the catheter through the apertures (92) and into association with other structures comprising the proximal portion (82) of the instrument. The proximal (88) and middle (84) portions of the catheter member (90) are shown in a substantially straight configuration, which is preferred for controllability of the more flexible distal portion (87). Indeed, the proximal (88) and middle (84) portions are structurally reinforced and made from stiffer materials to enhance torque transmission and insertability to the distal portion, while also providing enough cantilever bendability to facilitate access to remote tissue locations, such as the chambers of the heart.

[0206] FIG. 19 is a cross sectional view of the catheter member (90) at either the proximal (88) or middle (84) portion. At the center of the cross sectional construct is a central (or “working”) lumen (108), the geometry of which is selected in accordance with the requisite medical application. For example, in one embodiment it is desired to pass a commercially available ablation catheter having an outer diameter of about 7 French through the working lumen (108), in which case it is preferable to have a working lumen in the range of 7 French in diameter. The catheter member (90), and the entire system (32), for that matter, can be sized up or down in accordance with the desired procedure and tools. The proximal portion of the catheter member (90) may be reinforced with a stiffening member such as a braiding layer (98) which is preferably encapsulated on the outside by an outer layer (96) having at least one lumen (102) to accommodate a control element, such as a tension cable (not shown), and a low-friction inner layer (100) selected to provide a low-friction surface over the inside of the braiding layer (98). Four extruded lumens (102) are provided in the illustrated embodiment to accommodate four respective control elements (not shown).

[0207] To prevent relative rotational motion between the catheter member (90) and other structures which may surround it, the profile of the outer layer adjacent the control element lumens (102) may be increased. The cross section of the embodiment of FIG. 19 has a relatively low surface profile (104) adjacent the control element lumens (102), as compared with the cross section of the embodiment of FIG. 20, which is otherwise similar to that of FIG. 19. Indeed, within the same catheter member, it is preferable to have a more pronounced surface profile distally to interface with surrounding structures and prevent “wind up”, or torsional rotation, of the distal and middle portions of the catheter member. With the braiding layer (98) in the middle (84) and proximal (82) portions of the instrument, “wind up” is not as significant an issue, and therefore it is less important to have a pronounced surface profile to interface or “key” with other adjacent structures.

[0208] FIG. 21 depicts an embodiment having three control element lumens (102) disposed approximately equidistantly from each other about the perimeter of the catheter member (90) cross section. This embodiment illustrates by way of non-limiting example that the catheter member (90) need not be limited to configurations comprising four control element lumens or four control elements. By way of another example, FIG. 22 illustrates a non-equidistant, three-lumen (102) configuration, with two-lumen (102) and single lumen (102) variations shown in FIGS. 23 and 24, respectively.

[0209] To facilitate more dramatic bendability at the distal portion (87) of the catheter member (90), a reinforcing structure other than a braiding layer may be preferred. By way of non-limiting example, FIGS. 25-27 depict a metal spine (110) having a unique stress relief geometry cut into its walls. FIG. 28 depicts a cross section of an embodiment of a metal spine (110) to illustrate that the working lumen may be continued from the proximal (88) and middle (84) portions of the catheter member into the distal portion (87) through the center of the metal spine (110). Indeed, the metal spine preferably has similar inner and outer diameter sizes as the braiding layer (98) in the more proximal portions of the catheter member (90). Depending upon the metal utilized for the metal spine (110), very tight bend radius operation of the distal portion (87) of the catheter member (90) is possible, due in significant part to such a highly bendable reinforcing structure and its associated repeated stress relief pattern. To further enhance the flexibility of the distal portion (87) of the catheter member (90), softer polymeric materials may be utilized in the construct, such as Pebax™. For example, in one embodiment, the outer layer (96) in the proximal (88) and middle (84) portions of the catheter member (90) preferably comprise 70 durometer Pebax™, while in the distal portion (84) and outer layer (96) preferably comprise 35 or 40 durometer Pebax™.

[0210] Referring to FIGS. 29 and 30, one embodiment of a stress relief pattern is depicted in close-up view to illustrate that the pattern may be shifted by about ninety degrees with each longitudinal step along the spine (110) to maximize the homogeneity of stress concentration and bending behavior of the overall construct. To further enhance the flexibility of the metal spine, and clean up undesirable geometric discrepancies left behind after laser cutting, the metal spine may be chemically etched and electropolished before incorporation into the catheter member (90). As shown in FIG. 30, chemical etching takes the pattern from the original lasercut positioning (114) to a revised positioning (112) with larger windows in the pattern. In this embodiment, subsequent to chemical etching, the pattern forms a relief angle with sides (116a-116b, 118a-118b) with an intersection (120) and included angle (122). Preferred metal spine materials include, but are not limited to, stainless steel and nitinol.

[0211] Referring to FIGS. 31 and 32, the distal reinforcing structure may also comprise a polymeric spine (124) similarly configured to homogeneously bend due to a stress relief pattern comprising the tubular wall of the spine (124). In particular, due to the greater fracture toughnesses of many available polymeric materials, a more squared stress concentrating pattern may be repeated with polymer structures. Further, high-precision structures such as the depicted polymeric spine (124), may be formed using injection molding and/or other techniques less inexpensive than laser cutting and etching. As will be apparent to those skilled in the art, many other distal spine structures for concentrating and relieving stress may also be utilized to provide the requisite tight bend radius functionality distally within the catheter member (90) construct, including but not limited to coils and braids.

[0212] Referring to FIG. 33, a control element anchoring ring (126) is depicted having two anchoring lumens (128) for each incoming control element to be anchored at the distal tip of the catheter member (90). The anchoring ring (126) comprises the last rigid construct at the distal tip of the catheter member (90), beyond which only a low durometer polymeric atraumatic distal tip (not shown) extends, as the low friction liner (100) meets the outer layer (96) subsequent to these two layers encapsulating the anchoring ring (126). The anchoring ring (126) is the “anchor” into which the relatively high-tension control elements are fixedly inserted—and is therefore a key to the steerability and controllability of the catheter member (90) regardless of the number of control elements pulling upon it. In one embodiment, tension wire control elements (not shown) insert into the outermost of the anchoring lumens, then bend directly back into the innermost of the anchoring lumens, where they are soldered to the anchoring ring, which comprise machined or gold plated stainless steel for solderability.

[0213] FIGS. 35-49 depict certain aspects of a proximal portion (82) of an instrument (18) similar to that depicted in FIG. 19. Referring to FIG. 35, a control element interface assembly (132) is depicted, comprising an axel (54), a control element pulley (136), a manual adjustment knob (86), and a drive engagement knob (134). The manual adjustment knob is configured to facilitate manual adjustment of control element tensions during setup of the instrument upon the instrument driver. It is held in place against the axel (54) with a clamp screw (138), and houses a rotation range of motion limitation pin (140) which limits the range of motion of the axel subsequent to setup and tightening of the clamp screw. Referring to FIG. 35A, one embodiment of an axel (54) is depicted in isometric view without other hardware mounted upon it. Referring to FIG. 36, an axel (54) is depicted with a drive engagement knob (134) mounted upon it. The drive engagement knob (134) may take a shape similar to a screw with a long threaded portion configured to extend through the axel to engage a tapered nut (142), as shown. Twisting of the drive engagement knob (134) causes the tapered nut (142) to urge the teeth (144) of the axel outward (223), thereby engaging whatever structures surround the lower portion of the axel, including but not limited to a instrument driver interface socket (44).

[0214] FIGS. 37 and 38 depict respective orthogonal views of one embodiment of a control element pulley (136). The central hole (148) in the pulley (136) is sized for a press fit upon an axel, and the control element termination engagement slot (146) is configured to capture a control element terminator, such as a lead or steel cable terminator, that is pushed into the slot before a control element is wound around the pulley (136) during manufacture or rebuilding. Referring to FIG. 38, the pulley (136) preferably has a flanged shape (150) to facilitate winding and positional maintenance of a control element.

[0215] As shown in FIG. 39, the top portion (152) of one embodiment of a guide instrument base (48) comprises slots (154) to interface with the rotation range of motion limitation pins (140), which may be housed within a manual adjustment knob (86). FIG. 40 depicts a top view of the top portion (152). FIG. 41 depicts the same top portion (152), as viewed isometrically from underneath, to demonstrate how two pulleys may be mounted in related to the top portion (152) of the guide instrument base (48). The control element splay tracks (158) are employed to guide control elements (not shown) from apertures in a catheter member into pulleys which may be positioned within the pulley geometry accommodations (160) formed into the top portion (152) of the guide instrument base (48). Also shown in the top portion (152) is a catheter member geometry accommodation (162) and a seal geometry accommodation (164). FIG. 42 depicts an orthogonal view of the structures of FIG. 41 to better illustrate the control element splay track (158) structures positioned to guide control elements (not shown) away from a catheter member and over to a pulley associated with the top portion (152) of the guide instrument base (48).

[0216] Referring to FIG. 43, a bottom portion (156) of one embodiment of a guide instrument base (48) is configured to interface with a top portion (152) such as that depicted in FIGS. 39-42. The bottom portion (156) has two additional pulley geometry accommodations (160) and associated control element splay tracks (158). The top (152) and bottom (156) portions of the guide instrument base (48) are “sandwiched” together to capture the proximal portion (88) of a catheter member (90), and therefore the bottom portion (156) also has a catheter member geometry accommodation (162) and a seal geometry accommodation (164) formed into it. FIG. 44 depicts an orthogonal view of the structures of FIG. 43 to better illustrate the control element splay track (158) structures positioned to guide control elements (not shown) away from a catheter member and to a pulley associated with the bottom portion (156) of the guide instrument base (48). FIG. 45 depicts an underside isometric view of the same bottom portion (156) shown in FIGS. 43 and 44. The bottom surface may comprise magnets (166) to facilitate mounting of the instrument upon an instrument driver. The depicted embodiment also has mounting pin interface holes (168) formed through it to accommodate mounting pins from an instrument driver. Further, the bottom surface preferably has a generally asymmetric geometry to ensure that it will only fit an underlying instrument driver snugly in one way. FIG. 46 depicts an orthogonal view of the bottom portion (156) of the guide instrument base (48) embodiment of FIG. 45.

[0217] FIG. 47 illustrates a partially (although nearly completely) assembled instrument proximal end (82), including a top portion (152) and bottom portion (156) of an instrument base (48) interfaced together. The proximal end (82) houses four pulleys (not shown), a catheter member (90), and a seal (170), including and a purging port (172). Three manual adjustment knobs (86) are mounted to the guide instrument base (48) by axels (54), which are held in place by pulleys (not visible) mounted upon the axels (54). Rotational range of motion limitation pins (140) interface with the manual adjustment knobs and slots (154) in the guide instrument base (48) top portion (152). One of the four manual adjustment knobs is removed from the embodiment in FIG. 47 to illustrate the interaction between the pin (140) and slot (154). FIG. 48 shows the locations of the pulleys (136) and control element splay tracks (158) within this four-control element embodiment. Control elements (not shown) preferably comprise solid wires made from materials such as stainless steel, which are sized for the anticipated loads and geometric parameters of the particular application. They may be coated with materials such as Teflon™ to reduce friction forces. FIG. 49 illustrates a different isometric view of an instrument embodiment similar to that in FIG. 47 to better illustrate the seal (170) and purging port (172) positioning, as well as the clamp screws (138) of the manual adjustment knobs (86). The seal (170) preferably comprises a silicon rubber seal configured to accommodate insertion of working members or instruments, such as, e.g., relatively small profile guidewires (e.g., in the range of 0.035″ diameter), or relatively larger profile catheters (e.g., of up to 7 French or even larger).

[0218] Referring to FIGS. 50-73, other embodiments of instruments are depicted having the respective capabilities to drive two, three, or four control elements with less than four control element interface assemblies (132) as previously discussed. For ease in illustration, many of the same components are utilized in these embodiments. As will be appreciated by those skilled in the art, such component matching is by no means required to accomplish the described functions, and many alternative arrangements are possible within the scope of the inventions disclosed herein.

[0219] FIGS. 50, 51, and 52 illustrate an instrument (174) having two control element interface assemblies (132) is depicted in three orthogonal views. While this embodiment has only two control element interface assemblies, it is configured to drive four control elements and keep them in tension through either pre-tensioning, or active tensioning through a slotted guide instrument base (188) to a tensioning mechanism in the instrument driver (16). FIG. 53 illustrates an instrument (174) similar to that in FIG. 52, but shown from a back or bottom side orthogonal view. In particular, one side of the guide instrument base (188) forms slots (190) through which an instrument driver tensioning mechanism may keep control elements taut during operation of the instrument (174). FIG. 54 is a reverse orthogonal view of the structure in FIG. 53, with one side of the guide instrument base, and both control element interface assemblies, removed (132) to show the slots (190) and four control elements (192).

[0220] FIG. 55 illustrates an instrument (175) similar to that in FIGS. 53 and 54, with the exception that the guide instrument base (194) does not have slots—but rather has only fixed idler control element pathways to align the cables with the sets of two pulleys (136) comprising each control element interface assembly (132). In this embodiment, tension may be maintained in the control elements (192), with pre-tensioning, or pre-stressing, to prevent control element slack. FIG. 56 also illustrates an instrument (174) similar to that of FIGS. 53 and 54, including slots to allow for active tensioning of the control elements (192) from the underlying instrument driver. One of the control element interface assemblies (132) is shown intact, and one is shown only partially intact, with the axel (54) and drive engagement knob (134) depicted to show the control elements (192). A notable difference between the embodiment in FIG. 56 and that in FIG. 55 is the addition of the tensioning slots (190).

[0221] Referring to FIGS. 57 and 58, yet another instrument embodiment (176) is depicted in isometric and side views, respectively, with this embodiment having two control element interface assemblies to drive four control elements. As shown in the partial cutaway isometric view of FIG. 59, and close up cutaway view of FIG. 60, this embodiment differs from the fixed ider embodiment of FIG. 55, or the slotted embodiment of FIG. 56, in that it has four spring-loaded idlers to assist with tensioning each of the four control elements. Referring to FIG. 60, each of the control elements (192) passes through a spring loaded idler (198), which urges the control element (192) into tension by trying to rotate (200). This tensioning schema may be easiest to visualize in the orthogonal cutaway view of FIG. 61, wherein the spring loaded idlers (198) are depicted urging (200) the four control elements (192) into tension. The wireframe orthogonal view of FIG. 62 also shows the stacks of two pulleys each on each control element interface assembly (132) to accommodate four control elements (192).

[0222] FIGS. 63 and 64 depict another instrument embodiment (178), this one having three control element interface assemblies (132) for three independent control elements. As best seen in FIG. 64, this embodiment is similar to that of FIG. 47, for example, except that it has one less control element and one less control element interface assembly (132). FIG. 65 depicts yet another instrument embodiment (180) coupled with a sheath instrument (30). In particular, instrument (180) has two control element interface assemblies (132) and two control elements. As best seen in FIG. 66, the instrument (180) is not configured for slotted tensioning or spring-loaded tensioning. Instead, the control elements (192) of this embodiment may be actively tensioned independently, and/or pre-tensioned, to facilitate maintenance of tension for control purposes.

[0223] Referring to FIG. 67, yet another instrument embodiment (182) is shown coupled with a sheath instrument (30). Instrument (182) has a single control element interface assembly (132) and two control elements. As best seen in FIG. 68, instrument (182) is also not configured for slotted tensioning or spring-loaded tensioning. Instead, the control elements (192) of this embodiment may be pre-tensioned and kept in position with the help of a fixed idler control element pathway (196) to facilitate maintenance of tension for control purposes. FIG. 69 illustrates still another instrument embodiment (184), which is shown coupled with a sheath instrument (30). Instrument (184) has a single control element interface assembly (132) and two control elements (192), with a spring-loaded idler (198) tensioning of the control elements (192), as shown in FIG. 70. As with the aforementioned spring-loaded idler tensioning instrument embodiments, the spring-loaded idlers urge (200) the control elements (192) into tension to facilitate control.

[0224] FIG. 71 illustrates a still further instrument embodiment (186), which is shown coupled with a sheath instrument (30). Instrument (186) has a single control element interface assembly (132) and two control elements (192), with a single-slotted guide instrument base, as shown in FIG. 72. As with the aforementioned slotted-tensioning instrument embodiments, the slot facilitates tensioning of the control elements from a mechanism in the instrument driver below. FIG. 73 depicts the embodiment of FIG. 72, with both portions of the slotted guide instrument base (202) intact. Depending upon the amount of tensioning deflection within the slot (190), it may be desirable to remove the rotational range of motion limitation pin (not shown) from the manual adjustment knob (not shown) to prevent impingement of the pin, knob, and instrument base (202), as the control element interface assembly is moved in the slot (190) relative to the rest of the instrument base (202).

[0225] Referring to FIGS. 74-93, elements of a sheath instrument embodiment will now be described. Again, for ease in illustration, many of the same components from the previously described instrument embodiments is utilized in these further embodiments, although such component matching is by no means required to accomplish the described functions.

[0226] FIG. 74 depicts a guide instrument (18) shown coupled coaxially with a sheath instrument (30), together forming what has been described as a set of instruments (28). In FIGS. 75 and 76, the sheath instrument (30) is depicted without the guide instrument of FIG. 74. In FIG. 76, the sheath instrument (30) is depicted having one control element interface assembly (132), and preferably only one control element (not shown). From a functional perspective, in most embodiments the sheath instrument need not be as driveable or controllable as the associated guide instrument, because the sheath instrument is generally used to contribute to the remote tissue access schema by providing a conduit for the guide instrument, and to point the guide in generally the right direction. Such movement is controlled by rolling the sheath relative to the patient, bending the sheath in one or more directions with a control element, and inserting the sheath into the patient. The seal (204) is generally larger than the seal on the guide instrument due to the larger diameters of elongate members that may be inserted into the sheath instrument (30) as part of a medical procedure. Adjacent the seal (204) is an access port (206), which may be utilized to purge the instrument, or circulate fluids or instruments. The bottom (210) and top (212) portions of the sheath instrument base (48) are preferably sandwiched to house portions of the control element interface assembly, such as the single pulley in this embodiment, and the proximal portion of the sheath catheter member (208).

[0227] Referring to FIG. 77, the bottom portion of one embodiment of a sheath instrument base is depicted showing two magnets utilized to facilitate mounting against an instrument driver. Mounting pin interface holes (168) also assist in accurate interfacing with an instrument driver. The opposite surface is formed with a sheath catheter member geometry accommodation (214) to interface with the sheath catheter (not shown). FIG. 78 shows this opposite surface in further detail, having a pulley geometry accommodation (218), a seal geometry accommodation (216), and a sheath catheter geometry accommodation (214). There is also a control element splay track (220) similar to those depicted in reference to the embodiments of the guide instrument. In FIG. 79, a bottom view of a top portion (212) of one embodiment of a sheath instrument base (48) is depicted showing the sheath catheter geometry (214) and seal geometry (216) accommodations formed therein, and an axel interface hole (222) formed there through.

[0228] FIG. 80 illustrates yet another embodiment of the sheath catheter (208) in a pre-bent formation, which may be desirable depending upon the anatomical issue pertinent to the medical procedure. The sheath catheter (208) preferably has a construction somewhat similar to that of the aforementioned guide catheter member embodiments, with notable exceptions. For one, it preferably does not have a flexible structural element disposed within its distal end, as it is not within the preferred functionality of the sheath instrument to have very tight radius bendability, particularly given the high bendability of the associated guide instrument. Preferably both the proximal (224) and distal (226) portions comprise a low-friction inner layer, a braiding layer, and an outer layer, as described below with reference to FIG. 81. It is preferable to have more bending flexibility in the distal portion than in the proximal portion. This may be accomplished by selecting a outer layer polymeric material for the distal portion (226) having approximately half the durometer of the polymeric material utilized for the outer layer of the proximal portion (224). In the depicted embodiment, an atraumatic distal tip (228) comprising an extension of the low-friction inner layer and outer layer extends slightly beyond the termination of the braiding layer by between about ¼ inch and ⅛ inch to prevent damage to tissues in various medical procedures.

[0229] FIG. 81 is a cross sectional view of a proximal or distal portion of a sheath catheter member (208), similar to that shown in FIG. 80. A braiding layer (230) is surrounded by an outer layer (232) preferably comprising a polymer such as Pebax™ with a durometer between about 30 and 80, and an inner layer (234) preferably comprising a low-friction polymeric material into which one or more lumens may be optionally extruded. The embodiment of FIG. 81 depicts one control element lumen (236). The geometry of the inner layer (234) may be configured to “key” or restrictively interface with a guide catheter member outer geometry to prevent rotation of the guide catheter member as discussed below with reference to FIGS. 85-91. The central lumen (238) of the sheath catheter preferably is sized to closely fit the associated guide catheter member. FIG. 82 depicts an embodiment similar to that shown in FIG. 81, with the exception that it does not have a control element lumen. In some embodiments, it is preferable not to have a steerable sheath catheter, but instead to have a straight or pre-bent sheath catheter, or no sheath catheter at all, surrounding a portion of the guide catheter.

[0230] Referring to FIGS. 83 and 84, an embodiment of a sheath catheter member is depicted with an inner layer (234) configured to key with a 3-control-element guide geometry, such as that depicted in FIG. 21. FIG. 84 depicts a similar embodiment, without a control element lumen (236). FIG. 85 depicts an non-keyed sheath without any control element lumens to illustrate that keying and steerable control is not necessary or desired in some embodiments or procedures—particularly when more bendability of the sheath is desired. The embodiment of FIG. 85 is relatively thin walled, and while it still comprises a braiding layer (230) surrounded by an outer layer (232) and an inner layer (234) of polymeric material, it is generally more easily bendable through tortuous paths than are other more thick-walled embodiments. Further, without the keying geometry of the inner layer (234), the central lumen (238) is effectively larger.

[0231] FIGS. 86-91 illustrate cross sectional representations of various embodiments of coaxially coupled guide catheter (90) and sheath catheter (208) combinations.

[0232] Referring to FIG. 86, a relatively low surface profile (104) guide catheter is disposed within sheath catheter (208) having four control element lumens. The fit between the two structures is fairly loose, and some relative rotational displacement is to be expected if the guide catheter (90) is torqued significantly more than the sheath catheter (208). To help prevent such relative rotational displacement, a higher profile guide catheter (90) geometry may be utilized, as shown in FIG. 87, in order to decrease the freedom of movement between the two structures as they are bent through the pathways required by a medical procedure.

[0233] FIG. 88 depicts an embodiment similar to that in FIG. 87, but without the control element lumens. It may be desirable to have control element lumens formed into the walls of the guide catheter or sheath catheter for reasons other than passing control elements through such lumens. These lumens may function as stress relief structures to increase bendability. They may also be utilized to form preferred bending axes for the overall structure. Further, they may be utilized as working channels for flushing, drug delivery, markers, sensors, illumination fibers, vision fibers, and the like. It may be desirable to have a homogeneous patterning of control lumens across the cross section of a particular structure in order to promote homogeneous bending. For example, a sheath catheter with four control lumens, one of which is occupied by a control element in tension, may bend more homogeneously than a sheath catheter with only one or two control lumens, one of which occupied by a control element.

[0234] Referring to FIG. 89, a relatively high surface profile (106) guide catheter (90) is depicted within a non-keyed sheath catheter, with a 4-control-element guide catheter disposed within a pre-bent sheath instrument that is not remotely steerable. FIG. 90 depicts a similar embodiment to that of FIG. 89, with the exception of an even lower surface profile (104) guide catheter (90) disposed within the non-keyed sheath catheter. FIG. 91 depicts a somewhat extreme example of keying to resist relative rotational displacement between a guide catheter (90) and a sheath catheter (208). Significant resistance to rotational displacement is traded for higher degrees of overall system bendability, as will be apparent to those skilled in the art. As shown in FIG. 92, a preferably elastomeric seal (204) and access port (206) construct may be fitted onto the sheath catheter member (208), prior to mounting within the confines of the sheath instrument base (46). FIG. 93 is a side view of the sheath catheter member (208) coupled to the seal (204) and access port (206). FIG. 94 is an end view of the seal (204).

[0235] FIGS. 95-103 depict various aspects of embodiments of an instrument driver configured for use with the above-described instrument embodiments.

[0236] FIGS. 95 and 96 are simplified schematics that illustrate internal features and functionalities of one embodiment of an instrument driver. In FIG. 95, a carriage (240) is slidably mounted upon a platform (246), which is slidably mounted to a base structure (248). The slidable mounting (250) at these interfaces may be accomplished with high-precision linear bearings. The depicted system has two cables (256, 258) running through a plurality of pulleys (244) to accomplish motorized, synchronized relative motion of the carriage (240) and platform (246) along the slidable interfaces (250). As will be apparent to those skilled in the art, as the motor (242) pulls on the carriage displacement cable (256) with a tension force T, the carriage (240) feels a force of 2*T. Further, as the motor pulls the carriage displacement cable (256) by a displacement X, the carriage moves by X/2, and the platform moves by half that amount, or X/4, due to its “pulleyed” synchronization cable (258).

[0237] FIG. 96 illustrates a top view of a separate (but similar) system configured to drive an instrument interface pulley (260) associated with an instrument interface socket (262) to produce both directions of rotation independently from the position of the carriage (240), to which it is coupled, along the linear pathway prescribed by the slidable interfaces (250). With a mechanical schema similar to that in FIG. 96, as the motor (242) pulls a deflection X in the instrument interface cable (264), the same deflection is seen directly at the instrument interface pulley (260), regardless of the position of the carriage (240) relative to the motor (242), due to the synchronizing cable (266) positioning and termination (252).

[0238] Referring to FIGS. 97-103, systems similar to those depicted in FIGS. 95 and 96 are incorporated into various embodiments of the instrument driver. In FIG. 97, an instrument driver (16) is depicted as interfaced with a steerable guide instrument (18) and a steerable sheath instrument (30). FIG. 98 depicts an embodiment of the instrument driver (16), in which the sheath instrument interface surface (38) remains stationary, and requires only a simple motor actuation in order for a sheath to be steered using an interfaced control element via a control element interface assembly (132). This may be accomplished with a simple cable loop about a sheath socket drive pulley (272) and a capstan pulley (not shown), which is fastened to a motor, similar to the two upper motors (242) (visible in FIG. 98). The drive motor for the sheath socket drive schema is hidden under the linear bearing interface assembly.

[0239] The drive schema for the four guide instrument interface sockets (270) is more complicated, due in part to the fact that they are coupled to a carriage (240) configured to move linearly along a linear bearing interface (250) to provide for motor-driven insertion of a guide instrument toward the patient relative to the instrument driver, hospital table, and sheath instrument. The cabling and motor schema that moves the carriage (240) along the linear bearing interface (250) is an implementation of the diagrammatic view depicted in FIG. 95. The cabling and motor schema that drives each of the four depicted guide instrument interface sockets is an implementation of the diagrammatic view depicted in FIG. 96. Therefore, in the embodiments of FIGS. 98-103, wherein four separate cable drive loops serve four separate guide instrument interface sockets (270), and wherein the carriage (240) has motorized insertion, there is achieved a functional equivalent of a system such as that diagrammed in FIGS. 95 and 96, all fit into the same construct. Various conventional cable termination and routing techniques are utilized to accomplish a preferably high-density instrument driver structure with the carriage (240) mounted forward of the motors for a lower profile patient-side interface.

[0240] Still referring to FIG. 98, the instrument driver (16) is rotatably mounted to an instrument driver base (274), which is configured to interface with an instrument driver mounting brace (not shown), such as that depicted in FIG. 1, or a movable setup joint construct (not shown), such as that depicted in FIG. 2. Rotation between the instrument driver base (274) and an instrument driver base plate (276) to which it is coupled is facilitated by a heavy-duty flanged bearing structure (278). The flanged bearing structure (278) is configured to allow rotation of the body of the instrument driver (16) about an axis approximately coincident with the longitudinal axis of a guide instrument (not shown) when the guide instrument is mounted upon the instrument driver (16) in a neutral position. This rotation preferably is automated or powered by a roll motor (280) and a simple roll cable loop (286), which extends around portions of the instrument driver base plate and terminates as depicted (282, 284). Alternatively, roll rotation may be manually actuated and locked into place with a conventional clamping mechanism. The roll motor (280) position is more easily visible in FIG. 99.

[0241] FIG. 100 illustrates another embodiment of an instrument driver, including a group of four motors (290). Each motor (290) has an associated high-precision encoder for controls purposes and being configured to drive one of the four guide instrument interface sockets (270), at one end of the instrument driver. Another group of two motors (one hidden, one visible—288) with encoders (292) are configured to drive insertion of the carriage (240) and the sheath instrument interface socket (268).

[0242] Referring to FIG. 101, a further embodiment of an instrument driver is depicted to show the position of the carriage (240) relative to the linear bearing interfaces (250). Also shown is the interfacing of a portion of a instrument interface cable (264) as it bends around a pulley (244) and completes part of its loop to an instrument interface pulley (260) rotatably coupled to the carriage (240) and coupled to a guide instrument interface socket (270), around the instrument interface pulley (260), and back to a motor capstan pulley (294). To facilitate adjustment and installation of such cable loops, and due to the fact that there is generally no requirement to have a loop operating for a long period of time in one direction, thereby perhaps requiring a true unterminated loop, two ends of a cut cable loop preferably are terminated at each capstan (294).

[0243] The carriage (240) depicted in the embodiments of FIGS. 97-101 generally comprises a structural box configured to house the instrument interface sockets and associated instrument interface pulleys. Referring to FIGS. 102 and 103, a split carriage (296) is depicted, comprising a main carriage body (304) similar to that of the non split carriage depicted in previous embodiments (240), and either one or two linearly movable portions (302), which are configured to slide relative to the main carriage body (304) when driven along either forward or backward relative to the main carriage body by a gear (300) placed into one of the guide instrument interface sockets, the gear (300) configured to interface with a rack (298) mounted upon the main carriage body (304) adjacent the gear (300). In an alternate embodiment, the carriage need not be split on both sides, but may have one split side and one non-split side. Further, while a carriage with four guide instrument interface sockets is suitable for driving a guide instrument with anywhere from one to four control element interface assemblies, the additional hardware required for all four control element interface assemblies may be undesirable if an instrument only requires only one or two.

[0244] Referring to FIGS. 103.1-103.11, another variation of an instrument driver is depicted, comprising a variation of a split carriage design, such as that depicted in FIG. 103. As opposed to the embodiment of FIG. 103, wherein each instrument base interface is moved straight along a slot, or rotated, or both (independently), the embodiment of FIGS. 103.1-103.11 provides rotation and/or arcuate slot motion by a “winged” split carriage design, wherein the tension member pulleys and axles may be rotated about the axle axis, or moved along an arcuate pathway, independently.

[0245] Referring to FIG. 103.1, a winged split carriage instrument driver (135) is depicted coupled to a guide instrument (215) configured for the winged split carriage with a specialized guide instrument base (141) having two arcuate slots (145) as opposed to the straight slots of other embodiments, such as those described in reference to FIGS. 53, 54, and 72, for example. One or more electronics boards (139) preferably are coupled to the main housing structure (137) of the winged split carriage instrument driver (135). The depicted assembly also comprises a sheath instrument (30) movably threaded over at least a portion of the guide instrument (215) and coupled to the sheath frame block (185) which is coupled to the main housing structure (137) when the depicted assembly is fully assembled.

[0246] Referring to FIG. 103.2, a winged instrument driver guide instrument base (141) is depicted showing the arcuate slots (145) in greater detail, as well as a winged instrument driver guide instrument base top plate (143), which is configured to be fitted down upon the proximal tubular portion of a guide instrument catheter member (not shown) to maintain the relative positioning of the catheter member (not shown) relative to the winged instrument driver guide instrument base (141). An underside isometric view of the same structures depicted in FIG. 103.2 is depicted in FIG. 103.3. In the depicted embodiment, a low-profile control element interface assembly (147) is configured to rotate about the longitudinal axis of the interface assembly (219) while also slidably translating through the associated arcuate slot (145). FIG. 103.4 depicts an exploded view of the winged instrument driver guide instrument base top plate (143) and winged instrument driver guide instrument base (141) depicted in FIG. 103.2, also showing the arcuate slots (145) defined therein.

[0247] Referring to FIG. 103.5, a low-profile control element interface assembly (147) is shown in isometric view comprising a splined axle (157) coupled to a pulley flange (153), and also coupled to a set of control element pulleys (155) which are compressed between a low-profile manual adjustment knob (151) and the pulley flange (153) with a retaining fastener (149), such as a screw. An exploded view of the same structures is depicted in FIG. 103.6. Also shown in FIG. 103.6 is a pin (159) configured to prevent relative rotational displacement between the two control element pulleys (155) when the low-profile control element interface assembly (147) is assembled. The depicted embodiment of low-profile control element interface assembly (147) may be utilized with any of the aforementioned instrument base and instrument driver assemblies, subject to the requirement that the instrument interface sockets, labeled 44, for example in FIG. 6, preferably are also geometrically matched for a splined interface between socket and axle facilitating highly-efficient transfer of loads between the matched socket and axle. The low-profile control element interface assembly (147) preferably comprises polymers or metals which may be formed or machined into very high precision subassemblies or parts which are low in weight, high in hardness, and low in fracture toughness. In one embodiment, each of the components of the low-profile control element interface assembly (147) comprises polycarbonate or ultra-high-molecular-weight polyethylene.

[0248] Referring to FIG. 103.7, a winged split carriage assembly is depicted in semi-exploded view. The winged carriage base (173) is configured to rotatably support two independently rotatable wing structures (221), each comprising a bottom portion (165) and a top portion (163). A further exploded view of the wing structures (221) and associated members are depicted in FIG. 103.8. Rotatably coupled to the rotatable wing structures (221) is a set of control element pulleys (167) to which a splined instrument interface socket (161) is coupled. The winged carriage base (173) is configured to slidably couple to a carriage interface frame (not shown) with bearings (179). As shown in FIG. 103.9, slots (181) constrain the motion of the winged carriage base (173) relative to the carriage interface frame (191) to linear motion. Shafts and bearings are utilized to rotatably couple the wing structures (221) to the winged carriage base and facilitate rotational motion of the wing structures (221) about the axis of the pertinent coupling shaft (171). Similar shaft and bearing configurations are utilized to provide for rotation of the control element pulleys (167) relative to the wing structures (221). Thus, the winged split carriage design is configured to allow for independent motion of each of two wing structures (221), while also allowing for independent rotational motion of two sets of control element pulleys (167) and thereby instrument interface sockets (161). In other words, with a winged guide instrument (215) such as that depicted in FIG. 103.1 coupled to an arcuate slot instrument mounting base (187), and two control element interface assemblies (147) coupled to two instrument interface sockets positioned below the mounting base (187) in the configuration depicted in FIG. 103.1, each of the control element interface assemblies (147) may be rotated about their longitudinal axis, and also arcuately translated through the arcuate slot formed in the instrument base (141), to provide for tensioning and control of two control elements, one around each of the control element pulleys (167) on each of the control element interface assemblies (147), with actuation of a single control element interface assembly (147). Thus four control elements may be driven with the actuation of only two control element interface assemblies (147).

[0249] Referring to FIG. 103.10, an exploded view of an assembly similar to that depicted in FIG. 103.1 is depicted. Neither the sheath instrument, the two control element interface assemblies, nor the guide instrument catheter member are depicted in FIG. 103.10. As with aforementioned embodiments, the instrument driver roll assembly (195) and instrument driver motor/gear assembly (193) are coupled to the main frame (137) of the instrument driver. As shown in FIG. 103.11, redundant encoder readers (211) associated with each of four control element drive motors (209) of this embodiment facilitate high precision rotational position readings of the motor shafts and prevent position read errors. The motor output shafts are coupled to bevel gears (207) which are interfaced with another set of bevel gears (213) and thereby configured to drive the depicted vertical output shafts (205). The motor/gear interface block (203) is utilized to couple the motors, gears, and shafts into positions relative to each other and the main frame of the instrument driver (not shown), while constraining motions generally to rotational motions of shafts, motors, gears, and bearings. The rotation and arcuate translation of the winged structure instrument interface sockets (161) relative to the winged carriage base (173) and wing structures (221) is a key difference between the winged split carriage instrument driver and the non-winged embodiments described herein.

[0250] Referring to FIG. 104, an operator control station is depicted showing a control button console (8), a computer (6), a computer control interface (10), such as a mouse, a visual display system (4) and a master input device (12). In addition to “buttons” on the button console (8) footswitches and other known user control interfaces may be utilized to provide an operator interface with the system controls. Referring to FIG. 105A, in one embodiment, the master input device (12) is a multi-degree-of-freedom device having multiple joints and associated encoders (306). An operator interface (217) is configured for comfortable interfacing with the human fingers. The depicted embodiment of the operator interface (217) is substantially spherical. Further, the master input device may have integrated haptics capability for providing tactile feedback to the user. Another embodiment of a master input device (12) is depicted in FIG. 105B having a similarly-shaped operator interface (217). Suitable master input devices are available from manufacturers such as Sensible Devices Corporation under the trade name “Phantom™”, or Force Dimension under the trade name “Omega™”. In one embodiment featuring an Omega-type master input device, the motors of the master input device are utilized for gravity compensation. In other words, when the operator lets go of the master input device with his hands, the master input device is configured to stay in position, or hover around the point at which is was left, or another predetermined point, without gravity taking the handle of the master input device to the portion of the master input device's range of motion closest to the center of the earth. In another embodiment, haptic feedback is utilized to provide feedback to the operator that he has reached the limits of the pertinent instrument workspace. In another embodiment, haptic feedback is utilized to provide feedback to the operator that he has reached the limits of the subject tissue workspace when such workspace has been registered to the workspace of the instrument (i.e., should the operator be navigating a tool such as an ablation tip with a guide instrument through a 3-D model of a heart imported, for example, from CT data of an actual heart, the master input device is configured to provide haptic feedback to the operator that he has reached a wall or other structure of the heart as per the data of the 3-D model, and therefore help prevent the operator from driving the tool through such wall or structure without at least feeling the wall or structure through the master input device). In another embodiment, contact sensing technologies configured to detect contact between an instrument and tissue may be utilized in conjunction with the haptic capability of the master input device to signal the operator that the instrument is indeed in contact with tissue.

[0251] Referring to FIGS. 106-109, the basic kinematics of a catheter with four control elements is reviewed.

[0252] Referring to FIGS. 106 A-B, as tension is placed only upon the bottom control element (312), the catheter bends downward, as shown in FIG. 106A. Similarly, pulling the left control element (314) in FIGS. 107 A-B bends the catheter left, pulling the right control element (310) in FIGS. 108 A-B bends the catheter right, and pulling the top control element (308) in FIGS. 109 A-B bends the catheter up. As will be apparent to those skilled in the art, well-known combinations of applied tension about the various control elements results in a variety of bending configurations at the tip of the catheter member (90). One of the challenges in accurately controlling a catheter or similar elongate member with tension control elements is the retention of tension in control elements, which may not be the subject of the majority of the tension loading applied in a particular desired bending configuration. If a system or instrument is controlled with various levels of tension, then losing tension, or having a control element in a slack configuration, can result in an unfavorable control scenario.

[0253] Referring to FIGS. 10A-E, a simple scenario is useful in demonstrating this notion. As shown in FIG. 110A, a simple catheter (316) steered with two control elements (314, 310) is depicted in a neutral position. If the left control element (314) is placed into tension greater than the tension, if any, which the right control element (310) experiences, the catheter (316) bends to the left, as shown in FIG. 110B. If a change of direction is desired, this paradigm needs to reverse, and the tension in the right control element (310) needs to overcome that in the left control element (314). At the point of a reversal of direction like this, where the tension balance changes from left to right, without slack or tension control, the right most control element (314) may gather slack which needs to be taken up before precise control can be reestablished. Subsequent to a “reeling in” of slack which may be present, the catheter (316) may be may be pulled in the opposite direction, as depicted in FIGS. 10C-E, without another slack issue from a controls perspective until a subsequent change in direction.

[0254] The above-described instrument embodiments present various techniques for managing tension control in various guide instrument systems having between two and four control elements. For example, in one set of embodiments, tension may be controlled with active independent tensioning of each control element in the pertinent guide catheter via independent control element interface assemblies (132) associated with independently-controlled guide instrument interface sockets (270) on the instrument driver (16). Thus, tension may be managed by independently actuating each of the control element interface assemblies (132) in a four-control-element embodiment, such as that depicted in FIGS. 18 and 47, a three-control-element embodiment, such as that depicted in FIGS. 63 and 64, or a two-control-element embodiment, such as that depicted in FIGS. 56 and 66.

[0255] In another set of embodiments, tension may be controlled with active independent tensioning with a split carriage design, as described in reference to FIGS. 102 and 103. For example, with an instrument embodiment similar to that depicted in FIGS. 53, 54, and 56, a split carriage with two independent linearly movable portions, such as that depicted in FIG. 103, may be utilized to actively and independently tension each of the two control element interface assemblies (132), each of which is associated with two dimensions of a given degree of freedom. For example, there can be + and − pitch on one interface assembly, + and − yaw on the other interface assembly, with slack or tension control provided for pitch by one of the linearly movable portions (302) of the split carriage (296), and slack or tension control provided for yaw by the other linearly movable portion (302) of the split carriage (296).

[0256] Similarly, with an embodiment similar to that of FIGS. 71-73, slack or tension control for a single degree of freedom, such as yaw or pitch, may be provided by a single-sided split carriage design similar to that of FIG. 103, with the exception that only one linearly movable portion would be required to actively tension the single control element interface assembly of an instrument.

[0257] In another set of embodiments, tensioning may be controlled with spring-loaded idlers configured to keep the associated control elements out of slack, as in the embodiments depicted in FIGS. 57-62 and 69-70. The control elements preferably are pre-tensioned in each embodiment to prevent slack and provide predictable performance. Indeed, in yet another set of embodiments, pre-tensioning may form the main source of tension management, as in the embodiments depicted in FIGS. 55 and 67-68. In the case of embodiments only having pre-tensioning or spring-loaded idler tensioning, the control system may need to be configured to reel in bits of slack at certain transition points in catheter bending, such as described above in relation to FIGS. 110A and 110B.

[0258] To accurately coordinate and control actuations of various motors within an instrument driver from a remote operator control station such as that depicted in FIG. 1, an advanced computerized control and visualization system is preferred. While the control system embodiments that follow are described in reference to a particular control systems interface, namely the SimuLink™ and XPC™ control interfaces available from The Mathworks Inc., and PC-based computerized hardware configurations, many other configurations may be utilized, including various pieces of specialized hardware, in place of more flexible software controls running on PC-based systems.

[0259] Referring to FIG. 111, an overview of an embodiment of a controls system flow is depicted. A master computer (400) running master input device software, visualization software, instrument localization software, and software to interface with operator control station buttons and/or switches is depicted. In one embodiment, the master input device software is a proprietary module packaged with an off-the-shelf master input device system, such as the Phantom™ from Sensible Devices Corporation, which is configured to communicate with the Phantom™ hardware at a relatively high frequency as prescribed by the manufacturer. Other suitable master input devices, such as that (12) depicted in FIG. 105B are available from suppliers such as Force Dimension of Lausanne, Switzerland. The master input device (12) may also have haptics capability to facilitate feedback to the operator, and the software modules pertinent to such functionality may also be operated on the master computer (400). Preferred embodiments of haptics feedback to the operator are discussed in further detail below.

[0260] The term “localization” is used in the art in reference to systems for determining and/or monitoring the position of objects, such as medical instruments, in a reference coordinate system. In one embodiment, the instrument localization software is a proprietary module packaged with an off-the-shelf or custom instrument position tracking system, such as those available from Ascension Technology Corporation, Biosense Webster, Inc., Endocardial Solutions, Inc., Boston Scientific (EP Technologies), Medtronic, Inc., and others. Such systems may be capable of providing not only real-time or near real-time positional information, such as X-Y-Z coordinates in a Cartesian coordinate system, but also orientation information relative to a given coordinate axis or system. Some of the commercially-available localization systems use electromagnetic relationships to determine position and/or orientation, while others, such as some of those available from Endocardial Solutions, Inc.—St Jude Medical, utilize potential difference or voltage, as measured between a conductive sensor located on the pertinent instrument and conductive portions of sets of patches placed against the skin, to determine position and/or orientation. Referring to FIGS. 112A and 112B, various localization sensing systems may be utilized with the various embodiments of the robotic catheter system disclosed herein. In other embodiments not comprising a localization system to determine the position of various components, kinematic and/or geometric relationships between various components of the system may be utilized to predict the position of one component relative to the position of another. Some embodiments may utilize both localization data and kinematic and/or geometric relationships to determine the positions of various components.

[0261] As shown in FIG. 112A, one preferred localization system comprises an electromagnetic field transmitter (406) and an electromagnetic field receiver (402) positioned within the central lumen of a guide catheter (90). The transmitter (406) and receiver (402) are interfaced with a computer operating software configured to detect the position of the detector relative to the coordinate system of the transmitter (406) in real or near-real time with high degrees of accuracy. Referring to FIG. 112B, a similar embodiment is depicted with a receiver (404) embedded within the guide catheter (90) construction. Preferred receiver structures may comprise three or more sets of very small coils spatially configured to sense orthogonal aspects of magnetic fields emitted by a transmitter. Such coils may be embedded in a custom configuration within or around the walls of a preferred catheter construct. For example, in one embodiment, two orthogonal coils are embedded within a thin polymeric layer at two slightly flattened surfaces of a catheter (90) body approximately ninety degrees orthogonal to each other about the longitudinal axis of the catheter (90) body, and a third coil is embedded in a slight polymer-encapsulated protrusion from the outside of the catheter (90) body, perpendicular to the other two coils. Due to the very small size of the pertinent coils, the protrusion of the third coil may be minimized. Electronic leads for such coils may also be embedded in the catheter wall, down the length of the catheter body to a position, preferably adjacent an instrument driver, where they may be routed away from the instrument to a computer running localization software and interfaced with a pertinent transmitter.

[0262] In another similar embodiment (not shown), one or more conductive rings may be electronically connected to a potential-difference-based localization/orientation system, along with multiple sets, preferably three sets, of conductive skin patches, to provide localization and/or orientation data utilizing a system such as those available from Endocardial Solutions—St. Jude Medical. The one or more conductive rings may be integrated into the walls of the instrument at various longitudinal locations along the instrument, or set of instruments. For example, a guide instrument may have several conductive rings longitudinally displaced from each other toward the distal end of the guide instrument, while a coaxially-coupled sheath instrument may similarly have one or more conductive rings longitudinally displaced from each other toward the distal end of the sheath instrument—to provide precise data regarding the location and/or orientation of the distal ends of each of such instruments.

[0263] Referring back to FIG. 111, in one embodiment, visualization software runs on the master computer (400) to facilitate real-time driving and navigation of one or more steerable instruments. In one embodiment, visualization software provides an operator at an operator control station, such as that depicted in FIG. 1 (2), with a digitized “dashboard” or “windshield” display to enhance instinctive drivability of the pertinent instrumentation within the pertinent tissue structures. Referring to FIG. 113, a simple illustration is useful to explain one embodiment of a preferred relationship between visualization and navigation with a master input device (12). In the depicted embodiment, two display views (410, 412) are shown. One preferably represents a primary (410) navigation view, and one may represent a secondary (412) navigation view. To facilitate instinctive operation of the system, it is preferable to have the master input device coordinate system at least approximately synchronized with the coordinate system of at least one of the two views. Further, it is preferable to provide the operator with one or more secondary views which may be helpful in navigating through challenging tissue structure pathways and geometries.

[0264] Using the operation of an automobile as an example, if the master input device is a steering wheel and the operator desires to drive a car in a forward direction using one or more views, his first priority is likely to have a view straight out the windshield, as opposed to a view out the back window, out one of the side windows, or from a car in front of the car that he is operating. The operator might prefer to have the forward windshield view as his primary display view, such that a right turn on the steering wheel takes him right as he observes his primary display, a left turn on the steering wheel takes him left, and so forth. If the operator of the automobile is trying to park the car adjacent another car parked directly in front of him, it might be preferable to also have a view from a camera positioned, for example, upon the sidewalk aimed perpendicularly through the space between the two cars (one driven by the operator and one parked in front of the driven car), so the operator can see the gap closing between his car and the car in front of him as he parks. While the driver might not prefer to have to completely operate his vehicle with the sidewalk perpendicular camera view as his sole visualization for navigation purposes, this view is helpful as a secondary view.

[0265] Referring still to FIG. 113, if an operator is attempting to navigate a steerable catheter in order to, for example, contact a particular tissue location with the catheter's distal tip, a useful primary navigation view (410) may comprise a three dimensional digital model of the pertinent tissue structures (414) through which the operator is navigating the catheter with the master input device (12), along with a representation of the catheter distal tip location (416) as viewed along the longitudinal axis of the catheter near the distal tip. This embodiment illustrates a representation of a targeted tissue structure location (418), which may be desired in addition to the tissue digital model (414) information. A useful secondary view (412), displayed upon a different monitor, in a different window upon the same monitor, or within the same user interface window, for example, comprises an orthogonal view depicting the catheter tip representation (416), and also perhaps a catheter body representation (420), to facilitate the operator's driving of the catheter tip toward the desired targeted tissue location (418).

[0266] In one embodiment, subsequent to development and display of a digital model of pertinent tissue structures, an operator may select one primary and at least one secondary view to facilitate navigation of the instrumentation. By selecting which view is a primary view, the user can automatically toggle a master input device (12) coordinate system to synchronize with the selected primary view. In an embodiment with the leftmost depicted view (410) selected as the primary view, to navigate toward the targeted tissue site (418), the operator should manipulate the master input device (12) forward, to the right, and down. The right view will provide valued navigation information, but will not be as instinctive from a “driving” perspective.

[0267] To illustrate: if the operator wishes to insert the catheter tip toward the targeted tissue site (418) watching only the rightmost view (412) without the master input device (12) coordinate system synchronized with such view, the operator would have to remember that pushing straight ahead on the master input device will make the distal tip representation (416) move to the right on the rightmost display (412). Should the operator decide to toggle the system to use the rightmost view (412) as the primary navigation view, the coordinate system of the master input device (12) is then synchronized with that of the rightmost view (412), enabling the operator to move the catheter tip (416) closer to the desired targeted tissue location (418) by manipulating the master input device (12) down and to the right.

[0268] The synchronization of coordinate systems described herein may be conducted using fairly conventional mathematic relationships. For example, in one embodiment, the orientation of the distal tip of the catheter may be measured using a 6-axis position sensor system such as those available from Ascension Technology Corporation, Biosense Webster, Inc., Endocardial Solutions, Inc., Boston Scientific (EP Technologies), and others. A 3-axis coordinate frame, C, for locating the distal tip of the catheter, is constructed from this orientation information. The orientation information is used to construct the homogeneous transformation matrix, T_C0^G0, which transforms a vector in the Catheter coordinate frame “C” to the fixed Global coordinate frame “G” in which the sensor measurements are done (the subscript C₀ and superscript G₀ are used to represent the 0'th, or initial, step). As a registration step, the computer graphics view of the catheter is rotated until the master input and the computer graphics view of the catheter distal tip motion are coordinated and aligned with the camera view of the graphics scene. The 3-axis coordinate frame transformation matrix T_Gref^G0 for the camera position of this initial view is stored (subscripts G_ref and superscript C_ref stand for the global and camera “reference” views). The corresponding catheter “reference view” matrix for the catheter coordinates is obtained as:
T_Cref^C0=T_G0^C0T_Gref^G0T_Cref^Gref=(T_C0^G0)⁻¹T_Gref^G0T_C1^G1

[0269] Also note that the catheter's coordinate frame is fixed in the global reference frame G, thus the transformation matrix between the global frame and the catheter frame is the same in all views, i.e., T_G0^C0=T_Cref^Gref=T_Ci^Gi for any arbitrary view i. The coordination between primary view and master input device coordinate systems is achieved by transforming the master input as follows: Given any arbitrary computer graphics view of the representation, e.g. the i'th view, the 3-axis coordinate frame transformation matrix T_Gi^G0 of the camera view of the computer graphics scene is obtained form the computer graphics software. The corresponding catheter transformation matrix is computed in a similar manner as above:
T_Ci^C0=T_G0^C0T_Gi^G0T_Ci^Gi=(T_C0^G0)⁻¹T_Gi^G0T_Ci^Gi
The transformation that needs to be applied to the master input which achieves the view coordination is the one that transforms from the reference view that was registered above, to the current ith view, i.e., T_Cref^Ci. Using the previously computed quantities above, this transform is computed as:
T_Cref^Ci=T_C0^CiT_Cref^C0
The master input is transformed into the commanded catheter input by application of the transformation T_Cref^Ci. Given a command input

[0270] $r_{\mathrm{master}}=\left[\begin{array}{c}{x}_{\mathrm{master}}\\ y_{\mathrm{master}}\\ y_{\mathrm{master}}\end{array}\right],$
one may calculate:

[0271] $r_{\mathrm{catheter}}=\left[\begin{array}{c}{x}_{\mathrm{catheter}}\\ y_{\mathrm{catheter}}\\ y_{\mathrm{catheter}}\end{array}\right]=T_{\mathrm{Cref}}^{\mathrm{Ci}}\left[\begin{array}{c}{x}_{\mathrm{master}}\\ y_{\mathrm{master}}\\ y_{\mathrm{master}}\end{array}\right].$
Under such relationships, coordinate systems of the primary view and master input device may be aligned for instinctive operation.

[0272] Referring back to embodiment of FIG. 111, the master computer (400) also comprises software and hardware interfaces to operator control station buttons, switches, and other input devices which may be utilized, for example, to “freeze” the system by functionally disengaging the master input device as a controls input, or provide toggling between various scaling ratios desired by the operator for manipulated inputs at the master input device (12). The master computer (400) has two separate functional connections with the control and instrument driver computer (422): one (426) for passing controls and visualization related commands, such as desired XYZ) in the catheter coordinate system) commands, and one (428) for passing safety signal commands. Similarly, the control and instrument driver computer (422) has two separate functional connections with the instrument and instrument driver hardware (424): one (430) for passing control and visualization related commands such as required-torque-related voltages to the amplifiers to drive the motors and encoders, and one (432) for passing safety signal commands.

[0273] In one embodiment, the safety signal commands represent a simple signal repeated at very short intervals, such as every 10 milliseconds, such signal chain being logically read as “system is ok, amplifiers stay active”. If there is any interruption in the safety signal chain, the amplifiers are logically toggled to inactive status and the instrument cannot be moved by the control system until the safety signal chain is restored. Also shown in the signal flow overview of FIG. 111 is a pathway (434) between the physical instrument and instrument driver hardware back to the master computer to depict a closed loop system embodiment wherein instrument localization technology, such as that described in reference to FIGS. 112A-B, is utilized to determine the actual position of the instrument to minimize navigation and control error, as described in further detail below.

[0274] FIGS. 114-124 depict various aspects of one embodiment of a SimuLink™ software control schema for an embodiment of the physical system, with particular attention to an embodiment of a “master following mode.” In this embodiment, an instrument is driven by following instructions from a master input device, and a motor servo loop embodiment, which comprises key operational functionality for executing upon commands delivered from the master following mode to actuate the instrument.

[0275] FIG. 114 depicts a high-level view of an embodiment wherein any one of three modes may be toggled to operate the primary servo loop (436). In idle mode (438), the default mode when the system is started up, all of the motors are commanded via the motor servo loop (436) to servo about their current positions, their positions being monitored with digital encoders associated with the motors. In other words, idle mode (438) deactivates the motors, while the remaining system stays active. Thus, when the operator leaves idle mode, the system knows the position of the relative components. In auto home mode (440), cable loops within an associated instrument driver, such as that depicted in FIG. 97, are centered within their cable loop range to ensure substantially equivalent range of motion of an associated instrument, such as that depicted in FIG. 17, in both directions for a various degree of freedom, such as + and − directions of pitch or yaw, when loaded upon the instrument driver. This is a setup mode for preparing an instrument driver before an instrument is engaged.

[0276] In master following mode (442), the control system receives signals from the master input device, and in a closed loop embodiment from both a master input device and a localization system, and forwards drive signals to the primary servo loop (436) to actuate the instrument in accordance with the forwarded commands. Aspects of this embodiment of the master following mode (442) are depicted in further detail in FIGS. 119-124. Aspects of the primary servo loop and motor servo block (444) are depicted in further detail in FIGS. 115-118.

[0277] Referring to FIG. 119, a more detailed functional diagram of an embodiment of master following mode (442) is depicted. As shown in FIG. 119, the inputs to functional block (446) are XYZ position of the master input device in the coordinate system of the master input device which, per a setting in the software of the master input device may be aligned to have the same coordinate system as the catheter, and localization XYZ position of the distal tip of the instrument as measured by the localization system in the same coordinate system as the master input device and catheter. Referring to FIG. 120 for a more detailed view of functional block (446) of FIG. 119, a switch (460) is provided at block to allow switching between master inputs for desired catheter position, to an input interface (462) through which an operator may command that the instrument go to a particular XYZ location in space. Various controls features may also utilize this interface to provide an operator with, for example, a menu of destinations to which the system should automatically drive an instrument, etc. Also depicted in FIG. 120 is a master scaling functional block (451) which is utilized to scale the inputs coming from the master input device with a ratio selectable by the operator. The command switch (460) functionality includes a low pass filter to weight commands switching between the master input device and the input interface (462), to ensure a smooth transition between these modes.

[0278] Referring back to FIG. 119, desired position data in XYZ terms is passed to the inverse kinematics block (450) for conversion to pitch, yaw, and extension (or “insertion”) terms in accordance with the predicted mechanics of materials relationships inherent in the mechanical design of the instrument.

[0279] The kinematic relationships for many catheter instrument embodiments may be modeled by applying conventional mechanics relationships. In summary, a control-element-steered catheter instrument is controlled through a set of actuated inputs. In a four-control-element catheter instrument, for example, there are two degrees of motion actuation, pitch and yaw, which both have + and − directions. Other motorized tension relationships may drive other instruments, active tensioning, or insertion or roll of the catheter instrument. The relationship between actuated inputs and the catheter's end point position as a function of the actuated inputs is referred to as the “kinematics” of the catheter.

[0280] Referring to FIG. 125, the “forward kinematics” expresses the catheter's end-point position as a function of the actuated inputs while the “inverse kinematics” expresses the actuated inputs as a function of the desired end-point position. Accurate mathematical models of the forward and inverse kinematics are essential for the control of a robotically controlled catheter system. For clarity, the kinematics equations are further refined to separate out common elements, as shown in FIG. 125. The basic kinematics describes the relationship between the task coordinates and the joint coordinates. In such case, the task coordinates refer to the position of the catheter end-point while the joint coordinates refer to the bending (pitch and yaw, for example) and length of the active catheter. The actuator kinematics describes the relationship between the actuation coordinates and the joint coordinates. The task, joint, and bending actuation coordinates for the robotic catheter are illustrated in FIG. 126. By describing the kinematics in this way we can separate out the kinematics associated with the catheter structure, namely the basic kinematics, from those associated with the actuation methodology.

[0281] The development of the catheter's kinematics model is derived using a few essential assumptions. Included are assumptions that the catheter structure is approximated as a simple beam in bending from a mechanics perspective, and that control elements, such as thin tension wires, remain at a fixed distance from the neutral axis and thus impart a uniform moment along the length of the catheter.

[0282] In addition to the above assumptions, the geometry and variables shown in FIG. 127 are used in the derivation of the forward and inverse kinematics. The basic forward kinematics, relating the catheter task coordinates (X_c, Y_c, Z_c) to the joint coordinates (φ_pitch, φ_pitch, L), is given as follows:

[0283] $X_c=w\cos \left(\theta \right)$ $Y_c=R\sin \left(\alpha \right)$ $Z_c=w\sin \left(\theta \right)$ $\mathrm{where}$ $w=R\left(1-\cos \left(\alpha \right)\right)$ $\alpha ={\left[{\left({\varphi }_{\mathrm{pitch}}\right)}^2+{\left({\varphi }_{\mathrm{yaw}}\right)}^2\right]}^{1/2}\left(\mathrm{total}\mathrm{bending}\right)$ $R=\frac{L}{\alpha }\left(\mathrm{bend}\mathrm{radius}\right)$ $\theta =a\tan 2\left({\varphi }_{\mathrm{pitch}},{\varphi }_{\mathrm{yaw}}\right)\left(\mathrm{roll}\mathrm{angle}\right).$

[0284] The actuator forward kinematics, relating the joint coordinates (φ_pitch, φ_pitch, L) to the actuator coordinates (ΔL_x, ΔL_z, L) is given as follows:

[0285] ${\varphi }_{\mathrm{pitch}}=\frac{2\Delta L_z}{D_c}$ ${\varphi }_{\mathrm{yaw}}=\frac{2\Delta L_x}{D_c}$

[0286] As illustrated in FIG. 125, the catheter's end-point position can be predicted given the joint or actuation coordinates by using the forward kinematics equations described above.

[0287] Calculation of the catheter's actuated inputs as a function of end-point position, referred to as the inverse kinematics, can be performed numerically, using a nonlinear equation solver such as Newton-Raphson. A more desirerable approach, and the one used in this illustrative embodiment, is to develop a closed-form solution which can be used to calculate the required actuated inputs directly from the desired end-point positions.

[0288] As with the forward kinematics, we separate the inverse kinematics into the basic inverse kinematics, which relates joint coordinates to the task coordinates, and the actuation inverse kinematics, which relates the actuation coordinates to the joint coordinates. The basic inverse kinematics, relating the joint coordinates (φ_pitch, φ_pitch, L), to the catheter task coordinates (Xc, Yc, Zc) is given as follows:

[0289] ${\varphi }_{\mathrm{pitch}}=\alpha \sin \left(\theta \right)$ ${\varphi }_{\mathrm{yaw}}=\alpha \cos \left(\theta \right)$ $L=R\alpha \to \mathrm{where}\to \to \begin{array}{c}\theta =a\tan 2\left(Z_c,X_c\right)\\ R=\frac{l\sin \beta }{\sin 2\beta }\\ \alpha =\pi -2\beta \end{array}\to \begin{array}{c}\beta =a\tan 2\left(Y_c,W_c\right)\\ W_c={\left(X_c^2+Z_c^2\right)}^{1/2}\\ l={\left(W_c^2+Y_c^2\right)}^{1/2}\end{array}$

[0290] The actuator inverse kinematics, relating the actuator coordinates (ΔL_x, ΔL_z, L) to the joint coordinates (φ_pitch, φ_pitch, L) is given as follows:

[0291] $\Delta L_x=\frac{D_c{\varphi }_{\mathrm{yaw}}}{2}$ $\Delta L_z=\frac{D_c{\varphi }_{\mathrm{pitch}}}{2}$

[0292] Referring back to FIG. 119, pitch, yaw, and extension commands are passed from the inverse kinematics (450) to a position control block (448) along with measured localization data. FIG. 124 provides a more detailed view of the position control block (448). After measured XYZ position data comes in from the localization system, it goes through a inverse kinematics block (464) to calculate the pitch, yaw, and extension the instrument needs to have in order to travel to where it needs to be. Comparing (466) these values with filtered desired pitch, yaw, and extension data from the master input device, integral compensation is then conducted with limits on pitch and yaw to integrate away the error. In this embodiment, the extension variable does not have the same limits (468), as do pitch and yaw (470). As will be apparent to those skilled in the art, having an integrator in a negative feedback loop forces the error to zero. Desired pitch, yaw, and extension commands are next passed through a catheter workspace limitation (452), which may be a function of the experimentally determined physical limits of the instrument beyond which componentry may fail, deform undesirably, or perform unpredictably or undesirably. This workspace limitation essentially defines a volume similar to a cardioid-shaped volume about the distal end of the instrument. Desired pitch, yaw, and extension commands, limited by the workspace limitation block, are then passed to a catheter roll correction block (454).

[0293] This functional block is depicted in further detail in FIG. 121, and essentially comprises a rotation matrix for transforming the pitch, yaw, and extension commands about the longitudinal, or “roll”, axis of the instrument—to calibrate the control system for rotational deflection at the distal tip of the catheter that may change the control element steering dynamics. For example, if a catheter has no rotational deflection, pulling on a control element located directly up at twelve o'clock should urge the distal tip of the instrument upward. If, however, the distal tip of the catheter has been rotationally deflected by, say, ninety degrees clockwise, to get an upward response from the catheter, it may be necessary to tension the control element that was originally positioned at a nine o'clock position. The catheter roll correction schema depicted in FIG. 121 provides a means for using a rotation matrix to make such a transformation, subject to a roll correction angle, such as the ninety degrees in the above example, which is input, passed through a low pass filter, turned to radians, and put through rotation matrix calculations.

[0294] In one embodiment, the roll correction angle is determined through experimental experience with a particular instrument and path of navigation. In another embodiment, the roll correction angle may be determined experimentally in-situ using the accurate orientation data available from the preferred localization systems. In other words, with such an embodiment, a command to, for example, bend straight up can be executed, and a localization system can be utilized to determine at which angle the defection actually went—to simply determine the in-situ roll correction angle.

[0295] Referring briefly back to FIG. 119, roll corrected pitch and yaw commands, as well as unaffected extension commands, are output from the roll correction block (454) and may optionally be passed to a conventional velocity limitation block (456). Referring to FIG. 122, pitch and yaw commands are converted from radians to degrees, and automatically controlled roll may enter the controls picture to complete the current desired position (472) from the last servo cycle. Velocity is calculated by comparing the desired position from the previous servo cycle, as calculated with a conventional memory block (476) calculation, with that of the incoming commanded cycle. A conventional saturation block (474) keeps the calculated velocity within specified values, and the velocity-limited command (478) is converted back to radians and passed to a tension control block (458).

[0296] Tension within control elements may be managed depending upon the particular instrument embodiment, as described above in reference to the various instrument embodiments and tension control mechanisms. As an example, FIG. 123 depicts a pre-tensioning block (480) with which a given control element tension is ramped to a present value. An adjustment is then added to the original pre-tensioning based upon a preferably experimentally-tuned matrix pertinent to variables, such as the failure limits of the instrument construct and the incoming velocity-limited pitch, yaw, extension, and roll commands. This adjusted value is then added (482) to the original signal for output, via gear ratio adjustment, to calculate desired motor rotation commands for the various motors involved with the instrument movement. In this embodiment, extension, roll, and sheath instrument actuation (484) have no pre-tensioning algorithms associated with their control. The output is then complete from the master following mode functionality, and this output is passed to the primary servo loop (436).

[0297] Referring back to FIG. 114, incoming desired motor rotation commands from either the master following mode (442), auto home mode (440), or idle mode (438) in the depicted embodiment are fed into a motor servo block (444), which is depicted in greater detail in FIGS. 115-118.

[0298] Referring to FIG. 115, incoming measured motor rotation data from digital encoders and incoming desired motor rotation commands are filtered using conventional quantization noise filtration at frequencies selected for each of the incoming data streams to reduce noise while not adding undue delays which may affect the stability of the control system. As shown in FIGS. 117 and 118, conventional quantization filtration is utilized on the measured motor rotation signals at about 200 hertz in this embodiment, and on the desired motor rotation command at about 15 hertz. The difference (488) between the quantization filtered values forms the position error which may be passed through a lead filter, the functional equivalent of a proportional derivative (“PD”)+low pass filter. In another embodiment, conventional PID, lead/lag, or state space representation filter may be utilized. The lead filter of the depicted embodiment is shown in further detail in FIG. 116.

[0299] In particular, the lead filter embodiment in FIG. 116 comprises a variety of constants selected to tune the system to achieve desired performance. The depicted filter addresses the needs of one embodiment of a 4-control element guide catheter instrument with independent control of each of four control element interface assemblies for +/− pitch and +/− yaw, and separate roll and extension control. As demonstrated in the depicted embodiment, insertion and roll have different inertia and dynamics as opposed to pitch and yaw controls, and the constants selected to tune them is different. The filter constants may be theoretically calculated using conventional techniques and tuned by experimental techniques, or wholly determined by experimental techniques, such as setting the constants to give a sixty degree or more phase margin for stability and speed of response, a conventional phase margin value for medical control systems.

[0300] In an embodiment where a tuned master following mode is paired with a tuned primary servo loop, an instrument and instrument driver, such as those described above, may be “driven” accurately in three-dimensions with a remotely located master input device. Other preferred embodiments incorporate related functionalities, such as haptic feedback to the operator, active tensioning with a split carriage instrument driver, navigation utilizing direct visualization and/or tissue models acquired in-situ and tissue contact sensing, and enhanced navigation logic.

[0301] Referring to FIG. 128, in one embodiment, the master input device may be a haptic master input device, such as those available from Sensible Devices, Inc., under the trade name Phantom™, and the hardware and software required for operating such a device may at least partially reside on the master computer. The master XYZ positions measured from the master joint rotations and forward kinematics are generally passed to the master computer via a parallel port or similar link and may subsequently be passed to a control and instrument driver computer. With such an embodiment, an internal servo loop for the Phantom™ generally runs at a much higher frequency in the range of 1,000 Hz, or greater, to accurately create forces and torques at the joints of the master.

[0302] Referring to FIG. 129, a sample flowchart of a series of operations leading from a position vector applied at the master input device to a haptic signal applied back at the operator is depicted. A vector (344) associated with a master input device move by an operator may be transformed into an instrument coordinate system, and in particular to a catheter instrument tip coordinate system, using a simple matrix transformation (345). The transformed vector (346) may then be scaled (347) per the preferences of the operator, to produce a scaled-transformed vector (348). The scaled-transformed vector (348) may be sent to both the control and instrument driver computer (422) preferably via a serial wired connection, and to the master computer for a catheter workspace check (349) and any associated vector modification (350). This is followed by a feedback constant multiplication (351) chosen to produce preferred levels of feedback, such as force, in order to produce a desired force vector (352), and an inverse transform (353) back to the master input device coordinate system for associated haptic signaling to the operator in that coordinate system (354).

[0303] A conventional Jacobian may be utilized to convert a desired force vector (352) to torques desirably applied at the various motors comprising the master input device, to give the operator a desired signal pattern at the master input device. Given this embodiment of a suitable signal and execution pathway, feedback to the operator in the form of haptics, or touch sensations, may be utilized in various ways to provide added safety and instinctiveness to the navigation features of the system, as discussed in further detail below.

[0304] FIG. 130 is a system block diagram including haptics capability. As shown in summary form in FIG. 130, encoder positions on the master input device, changing in response to motion at the master input device, are measured (355), sent through forward kinematics calculations (356) pertinent to the master input device to get XYZ spatial positions of the device in the master input device coordinate system (357), then transformed (358) to switch into the catheter coordinate system and (perhaps) transform for visualization orientation and preferred controls orientation, to facilitate “instinctive driving.”

[0305] The transformed desired instrument position (359) may then be sent down one or more controls pathways to, for example, provide haptic feedback (360) regarding workspace boundaries or navigation issues, and provide a catheter instrument position control loop (361) with requisite catheter desired position values, as transformed utilizing inverse kinematics relationships for the particular instrument (362) into yaw, pitch, and extension, or “insertion”, terms (363) pertinent to operating the particular catheter instrument with open or closed loop control.

[0306] Referring to FIGS. 131-136, relationships pertinent to tension control via a split carriage design such as that depicted in FIGS. 102-103 are depicted to illustrate that such a design may isolate tension control from actuation for each associated degree of freedom, such as pitch or yaw of a steerable catheter instrument.

[0307] Referring to FIG. 131, some of the structures associated with a split carriage design, such as the embodiments depicted in FIGS. 102 and 103, include a linearly movable portion (302), a guide instrument interface socket (270), a gear (300), and a rack (298). Applying conventional geometric relationships to the physical state of the structures related in FIG. 131, the equations (364, 365) of FIG. 132 may be generated. Utilizing foreward kinematics of the instrument, such as those described above in reference to a pure cantilever bending model for a catheter instrument, the relationships of FIG. 133 may be developed for the amount of bending as a function of cable pull and catheter diameter (“Dc”) (366), and for tension (367), defined as the total amount of common pull in the control elements. Combining the equations of FIGS. 132 and 133, one arrives at the relationships (368, 369) depicted in FIG. 134, wherein desired actuation and desired tensioning are decoupled by the mechanics of the involved structures. Desired actuation (368) of the guide instrument interface socket (270) depicted in FIG. 131 is a function of the socket's angular rotational position. Desired tensioning (369) of the associated control elements is a function of the position of the tensioning gear (300) versus the rack (298).

[0308] Referring to FIG. 135, with a single degree of freedom actuated, such as +/− pitch or +/− yaw, and active tensioning via a split carriage mechanism, desired tension is linearly related to the absolute value of the amount of bending, as one would predict per the discussion above in reference to FIGS. 110A-E. The prescribed system never goes into slack—desired tension is always positive, as shown in FIG. 135. Referring to FIG. 136, a similar relationship applies for a two degree of freedom system with active tensioning—such as a four-cable system with +/− pitch and +/− yaw as the active degrees of freedom and active tensioning via a split carriage design. Since there are two dimensions, coupling terms (370) are incorporated to handle heuristic adjustments to, for example, minimize control element slacking and total instrument compression.

[0309] As discussed in reference to FIG. 113, in one embodiment, a tissue structure model (414) may be utilized to enhance navigation. It is particularly desirable to utilize actual data, acquired in situ, from the patient onto which a procedure is to be conducted, due to anatomic variation among the patient population which may be significant, depending generally upon the subject tissue structures. For example, the geometry of the left atrium of the human heart varies significantly from patient to patient, according to published reports and experimental verification in animals.

[0310] In one embodiment, focused magnetic resonance imaging, gated for heart cycle motion, and preferably gated for respiratory cycle motion, may be utilized along with conventional image cropping and thresholding techniques to produce a three dimensional tissue structure model. One of the challenges with such an imaging modality as applied to modeling active tissue structures such as those of the heart is the gating. In one embodiment, the gating comprises waiting for cardiac resting periods during diastole which are also correlated to substantially limited respiratory-induced motion. Acquiring a three-dimensional image of a left atrium, for example, utilizing gated magnetic resonance, may require an unacceptable amount of acquisition time, not to mention the generally large and expensive instrumentation required to accomplish the acquisition and fusion into a usable tissue structure model. Such a modality, however, may be preferred where cardiac and/or respiratory cyclic motion is negligible, and wherein an image or series of images may be acquired and synthesized into a usable tissue structure model comparatively quickly.

[0311] Referring to FIGS. 137-139 a technique is depicted through which a tissue structure model may be synthesized given appropriate hardware, such as an ultrasound transducer mounted upon a catheter or similar structure, and a localization system mounted upon the same structure to enable the capture of not only ultrasound slice data, but also the position and orientation of the transducer at the time of each slice acquisition. In other embodiments, a similar robotic system does not include a localization system, in which case kinematic and/or geometric relationships may be used to predict the location of the imaging device.

[0312] FIG. 137 depicts a human heart with a side-firing ultrasound catheter, such as those available under the trade name AcuNav™ by Siemens AG, entering the left atrium via the inferior vena cava blood vessel. Coupled to the ultrasound catheter, at or near the location of the ultrasound transducer, is a localization device, such as a set of orthogonally oriented electromagnetic receiving coils, to determine the position and orientation of the ultrasound transducer at each acquired “slice” of acquired reflected data. FIG. 138 is a view along the longitudinal axis of the distal end of the ultrasound catheter illustrating that, by rotating the ultrasound catheter, multiple slices (500) of reflected ultrasound image data, comprising multiple structural tissue mass location points, may be acquired, along with the position and orientation of the ultrasound transducer for each slice of reflected ultrasound data. With such an embodiment and a targeted tissue structure that is cyclically mobile, such the heart, each of the slices preferably is acquired during the resting period of diastole to prevent motion-based image distortion.

[0313] In post-acquisition processing, the acquired image slice data and associated position and orientation data may be utilized to construct a three-dimensional tissue structure model, such as that represented by the series of slices in FIG. 139. As will be apparent to those skilled in the art, to achieve a finer “mesh” of points for image formation, more slices may be acquired and assembled as shown in FIG. 139. Utilizing conventional image thresholding techniques available, for example, on most ultrasound mainframe devices, such as that sold under the trade name Sequoia™ by Siemens AG, points of transition between blood or other fluid-filled cavity and tissue mass may be clearly resolved to establish transition points such as those depicted in FIG. 138.

[0314] Referring to FIGS. 140-148, various aspects of another embodiment for acquiring a compiling a tissue structure image is depicted. Referring to FIG. 140, applying similar principles as applied in reference to the embodiment of FIGS. 137-139, a perimetrically-firing ultrasound image acquisition device, such as that sold under the trade name UltraICE™ by Boston Scientific Corporation, may be utilized in concert with a localization system to acquire a series of perimetric slices (502) and associated position and orientation data for the transducer (504) to assemble a series of tissue-cavity threshold points (506) related in space, as depicted in FIG. 141. As illustrated in FIG. 140, a series of related slices (502) is gathered as the transducer is inserted, retrieved, or both, through a cavity. As with the embodiment above, in the case of mobile heart tissue, each of the slices preferably is acquired during the resting period of diastole to prevent motion-based image distortion. Further, a finer resolution tissue structure image may be created with higher density image acquisition as the transducer is repositioned within the targeted cavity, as will be apparent to those skilled in the art.

[0315] Referring to FIG. 142, a close-up isometric view of a circumferentially-firing ultrasound catheter device (508) comprising a localization device (509) and an ultrasound transducer (510) is depicted within a tissue cavity acquiring a slice of data with an illustrative measured point at a detected density threshold at the transition between empty cavity and tissue wall. FIG. 143 depicts two views down the longitudinal axis of such a catheter system to depict acquisition of a series of density transition points about the catheter which form a slice which may be compiled into a larger three-dimensional image of the subject cavity. Referring to FIG. 144, the conventional transformation mathematics which may be utilized to transform position and orientation data within the acquiring catheter tip frame of reference to the ground frame of reference, or some other desired frame of reference. FIGS. 145A and 145B depict two different views of a catheter (512) inserting straight through a tissue cavity (513) and acquiring a series of data slices (514) along the way.

[0316] FIGS. 146A-D depict respective variations for imaging a given tissue structure geometry with the subject embodiment. In the embodiment depicted in FIG. 146A, a circumferentially-firing ultrasound catheter (515) is inserted straight through a cavity without regard to incoming slice data. In FIG. 146B, a variation is depicted wherein the catheter structure carrying the ultrasound transducer and localization device is bent as it moves through the subject tissue cavity to provide a series of slices occupying substantially parallel planes. FIG. 146C depicts a variation wherein the catheter structure carrying the ultrasound transducer and localization device is directed into specific sub-portions of the subject tissue mass. In one embodiment, such directing may be the result of real-time or near-real-time image analysis by the operator. For example, fluoroscopy or other conventional imaging techniques may be utilized to position the catheter into such a location in one embodiment. In another embodiment, the catheter may be automatically or semi-automatically guided to such as position, as discussed below. As shown in FIG. 146D, the catheter may be inserted and steered through the subject tissue cavity such that the planes of the slices of data acquired are not parallel. Given the known position and orientation of the ultrasound transducer from an associated localization system, it is by no means a requirement that the planes within a given image stack be parallel. Indeed, in some embodiments, it may be desirable to controllably bend an imaging catheter (516) near a location of interest to acquire multiple images (517) of a particular portion of the subject tissue, as depicted in FIG. 147. Such controlled bending through a preset range of motion as additional image slices are acquired may be termed “bend detailing” a particular portion of the subject tissue structures.

[0317] Referring to FIGS. 148A-C, several acquisition protocol embodiments are depicted for implementing the aforementioned acquisition system embodiment. In a simple embodiment (148A), an insertion vector is selected, subsequent to which an ultrasound transducer is inserted across a subject tissue cavity, pausing to acquire slice and position/orientation data along the way, leading to the combination of slice and location/orientation data into a three-dimensional model. In another embodiment (148B), rather than following a pre-determined program for inserting across the subject cavity and acquiring data slices, a closed-loop system analyzes incoming slice data and applies preprogrammed logic to automatically navigate as the image acquisition continues. FIG. 148C depicts an embodiment similar to that of FIG. 148B, with the exception that logical path planning is integrated into the controls logic operating the catheter instrument driver to provide automated or semi-automated image acquisition functionality. For example, the system may watch acquired images time-of-flight between emitted radiation and detected reflection of such radiation to steer the instrument directly down the middle of the cavity, as interpreted utilizing the time-of-flight data. This may be referred to as “time-of-flight center drive”. In another embodiment, significant changes in time-of-flight data for a given sector of an image series over a given period of time or distance may be interpreted as a change in tissue surface geometry worth higher density localized imaging, or even an automatic bending to take the transducer closer to the site of interest—or to rotate the transducer for higher-resolution imaging of the particular area without insertion adjustment, as described above in reference to FIG. 147.

[0318] FIGS. 149 and 150 depict respective embodiments for acquiring a three-dimensional tissue structure model of a human left atrium.

[0319] Referring to FIG. 149, subsequent to crossing the septal wall, confirming an acquisition start position adjacent the septum, and measuring the approximate trajectory and insertion length to reach the left superior pulmonary vein funnel into the left atrium with the instrument utilizing a conventional technology such as fluoroscopy or ultrasound, the instrument may be driven across the left atrium cavity along the approximate trajectory, gathering slices along the way and noting, via time of flight calculations and anatomy logic, approximate positioning of any other pulmonary vein funnel neckdown positions. As the instrument reaches the end of the predicted trajectory to the left inferior pulmonary vein funnel, neckdown into the funnel may be detected using time of flight calculations and added data from bend-detailing, as described above in reference to FIG. 147. After the neckdown is detected, the instrument may be driven into the funnel and funnel shape and trajectory data acquired for the left superior pulmonary vein structure. In one embodiment, a preset insertion limit prevents insertion beyond a set value into a pulmonary vein funnel structure. In another embodiment (such as that described in reference to FIG. 150), a tissue contact sensing means may be utilized to provide feedback to an operator or automated drive system that a tissue structure has been physically encountered by the instrument, and that the instrument insertion should be limited, as directed by the pertinent controls logic.

[0320] Referring still to FIG. 149, subsequent to acquiring funnel shape and trajectory data for a first pulmonary vein funnel of the left atrium, a similar procedure may be utilized to do the same for second, third, and fourth pulmonary vein funnels. After driving back out of the left superior pulmonary vein funnel, preferably along the trajectory utilized to minimally invasively enter the funnel, the neckdown into the left inferior pulmonary vein funnel is detected utilizing similar techniques, such as bend-detailing, and funnel and trajectory data pertinent to the left inferior pulmonary vein is acquired. Subsequently, the instrument may be driven back to the location of the right pulmonary vein neckdowns, preferably starting with the more easily accessed, in most patients, right inferior pulmonary vein neckdown. To increase the amount and variation of data comprising the ultimate left atrium model, data slices may be continually gathered as the instrument is driven back, forth, and around the left atrium.

[0321] After locating the right inferior pulmonary vein funnel, the instrument may be driven into the funnel and data acquired for the trajectory and shape, as discussed above in reference to the left pulmonary vein funnels. Similar, shape and trajectory data may be acquired for the right superior pulmonary vein funnel, which in most patients, is the most difficult to access due to its location relative to the septum. Should bend-detailing or acquisition of slices and time of flight analysis as facilitated by driving the instrument around within the atrium be ineffective in location any of the pulmonary vein neck down locations, conventional systems, such as fluoroscopy or intracardiac ultrasound, may be utilized during the depicted acquisition procedure to assist in generally driving the instrument to the location of the pertinent tissue structures, after which the appropriate portion of the depicted procedure may be resumed in a more automated fashion.

[0322] Referring to FIG. 150, another embodiment of a procedure for acquiring a three-dimensional image of a left atrium is depicted, this embodiment differing from that of FIG. 149 in that the pertinent system also incorporates a contact sensing means at the distal tip of the instrument for sensing contact between the instrument tip and the subject tissue structures. With such added functionality and logic to incorporate the information from it, the subject system may be configured to stop or indicate to the operator that a tissue structure or wall has been engaged. Such a feature may be utilized to streamline the acquisition process. For example, rather than planning a trajectory based upon data from imaging modalities such as fluoroscopy or ultrasound, the instrument merely may be pointed in roughly the appropriate direction across the left atrium toward the left pulmonary veins, and insertion driving and data slice acquisition engaged. The contact sensing feedback may be logically utilized to stop insertion of the instrument at or near the left wall of the left atrium, or within the bends of the pulmonary veins as they narrow away from the funnels of the left atrium.

[0323] A number of references have reported methods for determining contact between medical device instrumentation and tissue. For example, U.S. Pat. Nos. 5,935,079; 5,891,095; 5,836,990; 5,836,874; 5,673,704; 5,662,108; 5,469,857; 5,447,529; 5,341,807; 5,078,714; and Canadian Patent Application 2,285,342 disclose various aspects of determining electrode-tissue contact by measuring changes in impedance between an instrument electrode and a reference electrode. In an embodiment of the subject invention wherein the instrument comprises suitably positioned electrodes, techniques such as those disclosed in the art may be utilized. Other preferred embodiments of contact sensing means are described in reference to FIGS. 151-157.

[0324] Referring to FIG. 151, an instrument (518) operated by an instrument driver and a closed-loop control system incorporating a localization technology to measure actual instrument position is depicted. When the instrument tip is driven through a range of motion, such as + pitch to − pitch, then back to neutral and + yaw to − yaw, at some cyclic interval, loads encountered by tissue structure contact, as opposed to free cavity space in blood, for example, will tend to increase the error detected between the measured tip position determined by the localization system, and the predicted tip location, determined via the inverse kinematics of the instrument structure. Other cyclic patterns of motion may also be utilized, such as repeated spiral motion, circular motion, etc. Depending upon the experimentally determined systematic error between the predicted and measured tip locations in free space given a particular instrument structure, a threshold may be utilized, beyond which error is considered an indicator of tissue contact. Depending upon the cyclic motion pattern selected, the direction of contact between the instrument and another object may also be detected by observing the directionality of error between predicted and measured instrument position.

[0325] Referring to FIG. 152, a distal tip of an instrument (519) is depicted having two vibratory devices (520). In one embodiment, one device is a vibratory transmitter, such as a piezoelectric crystal adjacent a membrane, and the other device is a vibratory receiver comprising, for example, a membrane adjacent another piezoelectric crystal. In another embodiment, both devices, a single device, or more than two devices may comprise both transmitters and receivers. In free cavity space, the instrument will vibrate more freely than it will when in mechanical contact with a tissue structure, and in this embodiment, the difference is detected and logically interpreted as a tissue structure contact indicator.

[0326] Referring to FIGS. 153-155, another embodiment of a tissue contact sensing means is depicted wherein impedance monitoring through multiple paths at multiple frequencies may be utilized as an indicator of tissue contact. Conductivity measured through blood varies relatively little with frequency modulation, whereas conductivity does vary more significantly with frequency modulation when measured through a tissue structure. By quickly switching frequencies and taking measurements at various frequencies, using, for example, a microprocessor, one can make a determination regarding contact with tissue or not based upon the associated modulation in conductivity or impedance.

[0327] Such a technique may be combined with conductivity path modulation. Conventionally, impedance is measured between an instrument tip electrode and a dispersive ground mounted, for example, upon the skin of a patient's back. With such a configuration, conductivity increases, and impedance decreases, when the instrument is in contact with, for example, the heart wall. Another measurement path of interest is conductivity between an instrument tip electrode and another electrode inside of the same chamber, but at a more proximal instrument location. As blood is relatively highly conductive, conductivity will be at a maximum when the tip electrode is not in contact with tissue, and will decrease when the tip electrode touches a tissue wall, resulting in obscuring at least a portion of the tip electrode. Indeed, previous studies have shown conductivity or impedance measurements take with such a configuration can be utilized to predict contact before it actually occurs, and that depth of tip electrode penetration may also be predicted given the relationship between conductivity and obstruction of the tip electrode by tissue.

[0328] FIG. 153 depicts a further instrument embodiment (522) having a distal tip configured to facilitate such functionality. The instrument (522) has a tip electrode disposed distally, and four electrodes (524a-d) disposed more proximally at corner positions to facilitate contact with tissue structures as the instrument is positioned adjacent a tissue structure in a near parallel or tangential manner. FIG. 154 depicts the instrument (522) adjacent a tissue structure (523) with reference to a dispersive patch electrode (524) located upon the skin of a patient's back. With such a configuration, impedance may be monitored between any pair of electrodes, with various frequencies, to provide a configuration combining not only frequency modulation to detect tissue-electrode contact, but also conductivity comparison path modulation to detect tissue-electrode contact.

[0329] Referring to FIG. 155, a schematic is depicted for utilizing fast switching hardware, such as microprocessors, to collect data with each of the pertinent combinations. Each cycle of acquisition through the various combinations yields impedance difference monitoring based upon path switching and frequency switching, which may be compiled and logically associated with determinations of tissue contact or not, and even the location of the instrument which is predicted to be in contact with tissue. Many other variations of electrode arrays may be utilized in addition to the configuration depicted in FIG. 153, and frequency may be modulated between more than three frequencies, as depicted in FIG. 155, to produce additional data for each combination acquisition cycle.

[0330] FIGS. 156 and 157 depict another embodiment of a means for detecting contact between an instrument electrode and a tissue structure, such as a cardiac wall. The electrocardiogram (“ECG”) signal acquired by an instrument electrode positioned in free blood in the heart shows a discernable signal, but from a signal processing perspective, is less sharp and lower in amplitude due to the attenuation of high frequency signal content, as compared with similar signals detected when the electrode is in contact with a cardiac wall. When the ECG signal is differentiated with respect to time, the resulting differentiated signal has higher amplitude when the electrode is in contact, as compared with a slower-rising curve for a not-in-contact scenario. In one embodiment, a microcontroller or digital signal processor (“DSP”) is utilized to perform sampling, differentiation, and analysis of acquired ECG waveforms. In another embodiment, the shape of incoming ECG waveforms is monitored to detect not only contact, but proximity to contact as the waveform shape changes with proximity to the pertinent tissue structure.

[0331] Referring to FIG. 157, similar signal processing means are utilized to compare an intracardiac ECG signal (527) with a body surface ECG signal (528), which essentially represents a superposition of the various ECG waveforms from subportions of the heart. The fit between the intracardiac ECG signal is compared with the body surface ECG signal to determine whether the intracardiac ECG signal does indeed appear to be a portion of the combined signal represented by the body surface ECG signal. If the superposition match does not meet an experimentally determined threshold, the result is logically related to a state of non-contact between the intracardiac electrode and the heart wall tissue structures.

[0332] When the intracardiac electrode is in contact with a particular wall of the heart, the intracardiac ECG signal is crisp, detailed, and fits well into a portion of the superimposed combined body surface ECG signal, as depicted in FIG. 157. In another embodiment, the body surface ECG signal may be split into, for example, four subportions, each of which may be compared in a similar manner to the intracardiac ECG signal for a determination of not only contact, but also a confirmation of position within the heart as associated with the four subportions. For example, the body surface ECG signal may be subdivided into four portions representative of the four chambers of the heart, or even four portions of the same chamber.

[0333] In a generic form, the aforementioned “master following mode” may be logically configured to follow directly each command as it comes through the control system from the master input device. In one closed loop control embodiment, however, a logic layer is configured to interpret data incoming from a master input device and a localization system in light of the integrated tissue structure model and certain system settings information pertinent to the particular procedure at hand, to make modifications to commands forwarded to the master following and subsequent main servo loop controls logic, resulting in movements of the physical instrument.

[0334] Referring to FIGS. 158-160, some relatively simplistic examples illustrate challenges addressed by interpreted master following. The exemplary instrument embodiment depicted in each of these figures comprises a localization device and a contact sensing device. Many combinations or instrument componentry may be utilized with an interpreted master following logic layer to provide an operator with enhanced navigation functionality, depending upon the functional objectives.

[0335] As shown in FIG. 158, an instrument (530) has a distal end carrying a localization device (532) is positioned adjacent an irregular tissue wall which is represented in the system's visualization and control systems by a preferably three-dimensional tissue structure model acquired utilizing one of the aforementioned modalities. Supposing that the operator's objective is to move the instrument distal tip as indicated in FIG. 158, an operator's preferred movement path depends upon his preferred action in between the two locations. For example, if the operator merely wishes to touch the instrument (530) to the tissue wall in each location without contacting any tissue in between, the operator may prefer a path of efficiency around the irregularity in the tissue structure, such as that depicted by a dashed line (531). Following this path, the operator may drive the instrument between the respective positions/locations.

[0336] Additionally or alternately, the operator may wish to lightly touch the instrument (530) against the tissue structure and keep the instrument in contact as the instrument is driven between the locations depicted in FIG. 159 via a series of hops between the two locations, rather than a constant dragging type of contact as described in the aforementioned embodiment. Further, in another embodiment, as depicted in FIG. 160, the operator may wish to move the instrument between positions, while maintaining the instrument substantially normal to the tissue structure wall, perhaps due to the preferred orientation of a distal instrument feature, e.g., an electrode.

[0337] In addition, the operator may wish to have safety functionality built into the controls logic to, for example, prevent the instrument from damaging the subject tissue structures by excessively dragging along the tissue with an excessive load, overloading or overstressing a particular portion of a tissue structure with a concentrated load, or occupying a region that may cause tissue damage, such as an active valve entrance.

[0338] Such operator objectives are addressed in various embodiments of an interpreted master following logic layer interposed into the controls logic. In one embodiment, interpreted master following interprets commands that would normally lead to dragging along the tissue structure surface as commands to execute a succession of smaller “hops” to and from the tissue structure surface, while logging each contact as a new point to add to the tissue structure surface model. Hops are preferably executed by backing the instrument out the same trajectory it came into contact with the tissue structure, then moving normally along the wall per the tissue structure model, and re-approaching with a similar trajectory. In addition to saving to memory each new XYZ surface point, in one embodiment, the system saves the trajectory of the instrument with which the contact was made by saving the localization orientation data and control element tension commands to allow the operator to re-execute the same trajectory at a later time if so desired. By saving the trajectories and new points of contact confirmation, a more detailed contour map is formed from the tissue structure model, which may be utilized in the procedure and continually enhanced. The length of each hop may be configured, as well as the length of non-contact distance in between each hop contact.

[0339] In one embodiment, interpreted master following performs a variety of safety checking steps to ensure that the operator does not accidentally damage the subject tissue structure by driving into it or through it with the instrument. For example, the controls logic may be configured to disallow driving of the instrument beyond or into the subject tissue structure, as determined utilizing a tissue structure model with localization data and/or contact sensing. Such a mode may be manually overridden with an operator command in certain scenarios, for example, in order to purposefully puncture a tissue wall such as the septum at the location of the fossa ovalis. In one embodiment, the controls logic may be configured to prevent instrument electrode activation while the operator is attempting to move the instrument, or may attempt to prevent electrode activation in the same location for more than a predetermined time or amount of energy delivered.

[0340] In another embodiment, interpreted master following assists the operator in automating various clinical procedures. For example, where the instrument comprises a distal ablation electrode, the controls may be configured to automatically fit a circular ablation pattern through three contact points selected by the operator. Further, an operator may select a hopping, intermittent electrode burning pattern to automatically apply has he merely moves the master input device linearly. Haptics functionality may be utilized to provide the operator with various feedback to assist in clinical procedures. For example, a haptic “groove” may be created along the insertion axis of the instrument to assist the operator in driving the instrument with the master input device. Further, previously selected points of desired contact may be haptically turned in to “gravity wells” to assist the operator in directing the instrument to such locations.

[0341] A control system embodiment, such as described above, facilitates precision steerability of a catheter-based instrument in order to conduct a medical procedure. As an exemplary application, a myocardial ablation procedure to address atrial fibrillation will now be described with reference to FIGS. 161-174.

[0342] Referring to FIG. 161, a standard atrial approach is depicted with a robotically controlled guide catheter instrument (534) and sheath instrument (535) passing through the inferior vena cava and into the right atrium. Referring to FIG. 162, an imaging device, such as an intracardiac echo (“ICE”) sonography catheter (536), is forwarded into the right atrium to provide a field of view upon the interatrial septum. The guide instrument is driven to the septum wall, as shown in FIG. 163. Referring to FIGS. 164 and 165, the septum (537) may be crossed using a conventional technique of first puncturing the fossa ovalis location with a sharpened device (538), such as a needle or wire, passed through the working lumen of the guide instrument (534), then passing a dilator (539) over the sharpened device and withdrawing the sharpened device to leave the dilator (539), over which the guide instrument (534) may be advanced, as shown in FIG. 166. It may be desirable in some embodiments to pass an instrument arrangement through the working lumen of the guide instrument comprising a needle positioned coaxially within a dilator, as is well known in conventional (i.e., non-robotic) septum crossing techniques.

[0343] As shown in FIG. 167, subsequent to passing the guide instrument (534) across the septum (537), the guide instrument (534) may be utilized as a dilator to insert the sheath instrument (535) across the septum (537), thereby providing both instruments (534, 535) access and/or a view into the left atrium. It may be desirable to anchor the sheath instrument (535) in place just across the septum (537). For example, as shown in FIG. 168, an expanding structure such as a conventional balloon anchor (540) may be employed. As shown in FIG. 169, the guide instrument (534) may then be used to navigate inside the left atrium.

[0344] In one embodiment, a radio frequency (RF) ablation system is used with the robotic catheter system to supply energy to perform myocardial tissue ablation procedures in order block undesirable conduction pathways within the wall of the left atrium and adjoining vessels (e.g., pulmonary vein). By way of illustration, FIG. 170 depicts a system level view of such arrangement, including an operator control station (2), a computer (6), an instrument driver (16), a RF ablation energy control unit (541), a guide instrument (543) and a working instrument (547).

[0345] In one embodiment, shown in FIG. 171, a robotically controlled guide instrument (543), which may have an outer diameter of about 7 French, comprises an integrated ablation distal tip, and is passed through a sheath instrument (535). In another embodiment, shown in FIG. 172, a working instrument (547), in this instance an “off the shelf” ablation catheter such as that sold under the trade name Blazer™ by Boston Scientific Corporation, which may have an outer diameter of about 7 French, is passed through the working lumen of the guide instrument (534), which itself is passed through a sheath instrument (535). In such embodiments, the RF power may be supplied directly from the RF generator to the ablation catheter handle. Alternatively, the power supply may be coupled to the ablation catheter via a controller integrated with the robotic guide instrument in order to provide addition safety features, e.g., automatic power shut-off under defined circumstances. In such embodiments, only a small portion of the ablation catheter need be protruded beyond the distal tip of the guide instrument to expose the ablation electrodes, and the steering features which may be integrated into the “off the shelf” ablation catheter may not be needed as a result of the precision steerability provided by the robotically-controlled instrumentation through which the ablation catheter is coaxially positioned. Alternatively, a greater portion of the ablation catheter may be protruded beyond the distal tip of the guide instrument, preferably with the guide instrument held in a constant position by the system, and the manual steering functionality of the “off the shelf” ablation catheter may be utilized to place the distal portion of such device in a desired location, utilizing feedback to the operator from fluoroscopy, ultrasound, localization, or other real-time or near real-time systems. It will be appreciated by those skilled in the art that many of types of other ablation catheters or other working instruments may be passed through the working lumen of the guide instrument (534).

[0346] The precision provided by a system comprising a robotic guide instrument with an ablation catheter positioned coaxially within the robotic guide instrument facilitates precision mapping and creation of transmural lesions. In the right heart, without transseptal crossing, atrial flutter may be addressed by actively driving the distal tip of the ablation catheter to the lower right atrium. The right atrial isthmus may be contacted and ablated, along with the tricuspid annulus down to the junction of the right atrium and the inferior vena cava. Long linear lesions may be created through inputs to the master input device in various locations, such as the “intercavalline” between the superior vena cava and the inferior vena cava, or the “septal line” from the superior vena cava to the fossa ovalis, and then from the fossa ovalis down to the inferior vena cava. “Lasso” type ablation catheters may be driven using the subject robotic instrument system, to isolate pulmonary veins in the left heart, or conduct a segmental pulmonary vein isolation, wherein a subset of the electrodes positioned about the “Lasso” device are utilized to create ablation lesions. The procedure known as “Left Atrial Catheter Ablation” or “LACA”, developed by clinicians such as Pappone and Morady, may be facilitated using the subject system. LACA, which may involve large ablations to isolate the right superior pulmonary vein and right inferior pulmonary vein, along with ablative isolation of the left superior pulmonary vein and left inferior pulmonary vein, a connecting ablation between the aforementioned lesions (“roofline” ablation), and a left atrial isthmus linear ablation from the left inferior pulmonary vein to the mitral valve annulus, may be addressed utilizing the robotic precision of the subject system. Ablation targets such as the right inferior pulmonary vein and the ridge between the left superior pulmonary vein and the left inferior pulmonary vein may be particularly difficult without the precision of the subject system.

[0347] There are many well-known diagnostic or therapeutic distal end electrode configurations of working instruments that may used in conjunction with the guide instrument (534), such as those shown by way of non-limiting example in FIGS. 173A-D. Other tip options include non-contact means such as microwave or ultrasound energy (indicated by an “arrow” emitted from distal tip element 612 in FIG. 174A), optical laser energy (indicated by multiple “arrows” emitted from distal tip element 614 in FIG. 174B), a penetrating electrode or chemical/drug injection needle (element 616 in FIG. 174C), or mechanical grasper (element 618 in FIG. 174D).

[0348] In another embodiment, the instrument may be navigated by “direct visualization” utilizing conventional fiberscope or CCD camera devices, preferably disposed within a distally-positioned viewing balloon containing a substantially clear fluid such as saline when in a blood environment. In yet another embodiment, an infrared visualization technology, such as those available from CardioOptics Corporation, may be coupled to the instrument to provide direct visualization through a blood or similar medium without a viewing balloon or similar structure. In another embodiment wherein the instrument is navigated in a non-blood space, a viewing balloon need not be positioned to protect the camera device, and the camera lens or image intake may be positioned at the distal tip of the instrument. Whether the direct visualization device is assisted by a balloon-like visualization structure or not, the device preferably is coupled to the instrument either by insertion through the working lumen of an embodiment of the instrument, or integrated into one of the walls comprising the elongate instrument.

[0349] Conventional sensors may be disposed at and/or around the distal tip of the instrument, such as those which comprise strain gages and/or piezoelectric crystals. Also, more than one localization device may be coupled to the instrument along different positions of the instrument to allow for more complex monitoring of the position of the instrument. Such additional information may be utilized to help compensate for body movement or respiratory cycle related movement of tissues relative to a base coordinate system.

[0350] In still another embodiment of the tissue structure model acquisition modalities described above, including a contact sensor, the instrument may merely be driven around, in a planned fashion, or even at random, within a cavity to collect and store all points of contact to develop a three-dimensional model of the tissue structures. In a related embodiment, a rough model acquired utilizing a conventional imaging modality such as ultrasound or fluoroscopy may be utilized as a starting point, and then additional points added, particularly at points of interest, such as pulmonary vein and valve locations within the left atrium, utilizing a “tapping around” pattern with contact sensing to gather more points and refine the model.

[0351] As described above in reference to FIG. 113, in one embodiment, visualization software provides an operator at an operator control station, such as that depicted in FIG. 1 (2), with a digitized “dashboard” or “windshield” display to enhance instinctive driveability of the pertinent instrumentation within the pertinent tissue structures.

[0352] It may be useful to present the operator with one or more views of various graphical objects in an overlayed format, to facilitate the user's comprehension of relative positioning of the various structures. For example, it may be useful to overlay a real-time fluoroscopy image with digitally-generated “cartoon” representations of the predicted locations of various structures or images. Indeed, in one embodiment, a realtime or updated-as-acquired fluoroscopy image including a fluoroscopic representation of the location of an instrument may be overlayed with a realtime representation of where the computerized system expects the instrument to be relative to the surrounding anatomy. In a related variation, updated images from other associated modalities, such as intracardiac echo ultrasound (“ICE”), may also be overlayed onto the display with the fluoro and instrument “cartoon” image, to provide the operator with an information-rich rendering on one display.

[0353] Referring to FIG. 175, a systemic view configured to produce such an overlayed image is depicted. As shown in FIG. 175, a conventional fluoroscopy system (330) outputs an electronic image in formats such as those known as “S-video” or “analog high-resolution video”. In image output interface (332) of a fluoroscopy system (330) may be connected to an input interface of a computer (342) based image acquisition device, such as those known as “frame grabber” (334) image acquisition cards, to facilitate intake of the video signal from the fluoroscopy system (330) into the frame grabber (334), which may be configured to produce bitmap (“BMP”) digital image data, generally comprising a series of Cartesian pixel coordinates and associated grayscale or color values which together may be depicted as an image. The bitmap data may then be processed utilizing computer graphics rendering algorithms, such as those available in conventional “OpenGL” graphics libraries (336). In summary, conventional OpenGL functionality enables a programmer or operator to define object positions, textures, sizes, lights, and cameras to produce three-dimensional renderings on a two-dimensional display. The process of building a scene, describing objects, lights, and camera position, and using OpenGL functionality to turn such a configuration into a two-dimensional image for display is known in computer graphics as “rendering”. The description of objects may be handled by forming a mesh of triangles, which conventional graphics cards are configured to interpret and output displayable two-dimensional images for a conventional display or computer monitor, as would be apparent to one skilled in the art. Thus the OpenGL software (336) may be configured to send rendering data to the graphics card (338) in the system depicted in FIG. 175, which may then be output to a conventional display (340).

[0354] In one embodiment, a triangular mesh generated with OpenGL software to form a cartoon-like rendering of an elongate instrument moving in space according to movements from, for example, a master following mode operational state, may be directed to a computer graphics card, along with frame grabber and OpenGL processed fluoroscopic video data. Thus a moving cartoon-like image of an elongate instrument would be displayable. To project updated fluoroscopic image data onto a flat-appearing surface in the same display, a plane object, conventionally rendered by defining two triangles, may be created, and the updated fluoroscopic image data may be texture mapped onto the plane. Thus the cartoon-like image of the elongate instrument may be overlayed with the plane object upon which the updated fluoroscopic image data is texture mapped. Camera and light source positioning may be pre-selected, or selectable by the operator through the mouse or other input device, for example, to enable the operator to select desired image perspectives for his two-dimensional computer display. The perspectives, which may be defined as origin position and vector position of the camera, may be selected to match with standard views coming from a fluoroscopy system, such as anterior/posterior and lateral views of a patient lying on an operating table. When the elongate instrument is visible in the fluoroscopy images, the fluoroscopy plane object and cartoon instrument object may be registered with each other by ensuring that the instrument depicted in the fluoroscopy plane lines up with the cartoon version of the instrument. In one embodiment, several perspectives are viewed while the cartoon object is moved using an input device such as a mouse, until the cartoon instrument object is registered with the fluoroscopic plane image of the instrument. Since both the position of the cartoon object and fluoroscopic image object may be updated in real time, an operator, or the system automatically through image processing of the overlayed image, may interpret significant depicted mismatch between the position of the instrument cartoon and the instrument fluoroscopic image as contact with a structure that is inhibiting the normal predicted motion of the instrument, error or malfunction in the instrument, or error or malfunction in the predictive controls software underlying the depicted position of the instrument cartoon.

[0355] Referring back to FIG. 175, other video signals (not shown) may be directed to the image grabber (334), besides that of a fluoroscopy system (330), simultaneously. For example, images from an intracardiac echo ultrasound (“ICE”) system, intravascular ultrasound (“IVUS”), or other system may be overlayed onto the same displayed image simultaneously. Further, additional objects besides a plane for texture mapping fluoroscopy or a elongate instrument cartoon object may be processed using OpenGL or other rendering software to add additional objects to the final display.

[0356] Referring to FIGS. 176A-B and FIG. 177, one embodiment is illustrated wherein the elongate instrument is a robotic guide catheter, and fluoroscopy and ICE are utilized to visualize the cardiac and other surrounding tissues, and instrument objects. Referring to FIG. 176A, a fluoroscopy image has been texture mapped upon a plane configured to occupy nearly the entire display area in the background. Visible in the fluoroscopy image as a dark elongate shadow is the actual position, from fluoroscopy, of the guide catheter instrument relative to the surrounding tissues. Overlayed in front of the fluoroscopy plane is a cartoon rendering (white in color in FIGS. 176A and 176B) of the predicted, or “commanded”, guide catheter instrument position. Further overlayed in front of the fluoroscopy plane is a small cartoon object representing the position of the ICE transducer, as well as another plane object adjacent the ICE transducer cartoon object onto which the ICE image data is texture mapped by a technique similar to that with which the fluoroscopic images are texture mapped upon the background plane object. Further, mouse objects, software menu objects, and many other objects may be overlayed. FIG. 176B shows a similar view with the instrument in a different position. For illustrative purposes, FIGS. 176A and 176B depict misalignment of the instrument position from the fluoroscopy object, as compared with the instrument position from the cartoon object. As described above, the various objects may be registered to each other by manually aligning cartoon objects with captured image objects in multiple views until the various objects are aligned as desired. Image processing of markers and shapes of various objects may be utilized to automate portions of such a registration process.

[0357] Referring to FIG. 177, a schematic is depicted to illustrate how various objects, originating from actual medical images processed by frame grabber, originating from commanded instrument position control outputs, or originating from computer operating system visual objects, such as mouse, menu, or control panel objects, may be overlayed into the same display.

[0358] In another embodiment, a preacquired image of pertinent tissue, such as a three-dimensional image of a heart, may be overlayed and registered to updated images from realtime medical imaging modalities as well. For example, in one embodiment, a beating heart may be preoperatively imaged using gated computed tomography (“CT”). The result of CT imaging may be a stack of CT data slices. Utilizing either manual or automated thresholding techniques, along with interpolation, smoothing, and/or other conventional image processing techniques available in software packages such as that sold under the tradename Amira™, a triangular mesh may be constructed to represent a three-dimensional cartoon-like object of the heart, saved, for example, as an object (“.obj”) file, and added to the rendering as a heart object. The heart object may then be registered as discussed above to other depicted images, such as fluoroscopy images, utilizing known tissue landmarks in multiple views, and contrast agent techniques to particularly see show certain tissue landmarks, such as the outline of an aorta, ventricle, or left atrium. The cartoon heart object may be moved around, by mouse, for example, until it is appropriately registered in various views, such as anterior/posterior and lateral, with the other overlayed objects.

[0359] Referring to FIG. 178, a distributed system architecture embodiment is depicted. A master control computer running a realtime operating system, such as QNX, is connected to each of the other computers in the system by a 1 gigabit Ethernet “Realtime Network”, and also by a 100 megabit Ethernet “System Network”, using a conventional high-speed switch. This enables localized custom computing for various devices to be pushed locally near the device, without the need for large cabling or a central computing machine. In one embodiment, the master control computer may be powered by an Intel Xeon dual processor architecture, the visualization computer powered by a high-end X86 Intel architecture PC running Windows XP and having multiple video cards and frame grabbers, the instrument driver and master input device CPUs being PC 104 or “EPIC” standard boards with two Ethernet connections for the two networks. An additional master input device, touchscreen, and console may be configured into an addition operator workstation in a different location relative to the patient. The system is very expandeable—new devices may be plugged into the switch and placed onto either of the two networks. Referring to FIG. 178, two high resolution frame grabber boards (374) acquire images from two fluoro devices (or one in the case of single plane fluoro), which a nominal resolution frame grabber board (373) acquires images from an intracardiac echo system. Such image data may be utilized for overlaying, etc, as described in reference to FIGS. 175 177, and displayed on a display, such as the #2 display, using a video card (372) of the visualization computer, as depicted. Heart monitor data, from systems such as those distributed by Prucka, may be directly channeled from video out ports on the heart monitor device to one of the displays. Such data may also be acquired by a frame grabber. Similarly, electrophysiological mapping and treatment data and images from systems available from distributors such as Endocardial Solutions, Biosense Webster, etc, may be directed as video to a monitor, or data to a data acquisition board, databus, or frame grabber. Preferably the master control computer has some interface connectivity with the electrophysiology system as well to enable single master input device driving of such device, etc. Referring to FIG. 179 a depiction of the software and hardware interaction is depicted. Essentially, the master state machine functionality of the master control system realtime operating system allows for very low latency control of processes used to operate master input device algorithms and instrument driver algorithms, such as those described in reference to the control systems description above. Indeed, XPC may be utilized to develop algorithm code, but preferably a universal modeling language such as rational rose by IBM or Rhapsody by ILogix, is utilized to build code and documentation using a graphical interface. With the gigabit realtime network, in a matter of 200-300 microseconds, the master input device or instrument driver algorithms are able to communicate with FPGA driver code in the electronics and hardware near the pertinent device to exchange new values, etc, and confirm that all is well from a safety perspective. This leaves approximately 700 microseconds for processing if a 1 millisecond motor shutoff time is required if all is not well—and this is easily achievable with the described architecture. The visualization PC may be configured to cycle data from the master control computer at a lower frequency, about 20 milliseconds.

[0360] Referring to FIG. 181, common features may be accessed by a console. Sheath control buttons for roll, bend, and insert, when depressed one at a time, cause the master input device to control roll of the sheath (in one embodiment, this meaning roll of the entire instrument driver) in one direction or another as directed by the master input device, +/− bending in one direction, and insertion of the sheath relative to the guide instrument. Instinctive control buttons determine whether the main display is to synchronize master input device movement with 3-D images, such as CT images, or fluoro images. An autoretract button pulls in the guide instrument to a zero insertion point along the trajectory that it was bent. A trackball and mouse select buttons may be used for some features not accessed by a touch screen interface. Record features record a digital clip of video on a selected monitor for a preset period of time, or acquire an image of the video on a selected monitor. Camera controls enable the operator to pan or zoom an image featured on a display.

[0361] Referring to FIGS. 182 186D, a touchscreen interface provides a palate for virtually unlimited control configuration. Various embodiments of patient data setup, operator preset, data storage and retrieval, and operational procedure aspects may be coded into the touch screen interface for easy access during an operation.

[0362] Referring to FIGS. 187A-200C, several embodiments of minimally invasive instruments and kits thereof which may be preferred for a cardiac ablation procedure in accordance with the present invention are depicted.

[0363] Referring to FIGS. 187A-188B, various aspects of one embodiment of a sheath instrument 180 are depicted. The finished assembly of the depicted embodiment preferably has an inner lumen of about 145 mils and 158 mils (noncircular x-section, the former being the smaller inner lumen diameter, or “I.D.”, the latter being the larger I.D.) which is configured to fit the outer finish diameter, or “O.D.”, of a guide instrument such as that described in reference to FIGS. 189A-189C, which has an inner diameter of approximately 8 French—a size configured to fit several approved off-the-shelf ablation catheters, as well as needle/dilator sets such as those described below.

[0364] Referring to FIG. 187A, the depicted sheath instrument embodiment (227) comprises a sheath catheter member (208) which is proximally coupled to a sheath instrument base (46) which is coupled to a control element interface assembly (147) and Luer assembly (225). The control element interface assembly (147), similar to those described in reference to FIGS. 103.5 and 103.6, for example, has a splined axle (157) configured to interface with an instrument driver interface socket (not shown, see item 44 of FIG. 6, for example). The total working length of the portion of the catheter member (208) distal of the sheath instrument base (46) is approximately 78 centimeters in the depicted embodiment. Approximately 2.5 inches from the distal tip (237), a proximal ring (233) is integrated into the assembly to provide not only radio-opacity for fluoroscopy, and also conductivity for a potential difference type localization integration as discussed above, but also for termination and return of a proximal control element (not shown in FIG. 187A) which, in the depicted embodiment, is configured to extend from the one or more pulleys (not shown in FIG. 187A) associated with the manual adjustment knob (229) to the proximal ring (233) and back to the one or more pulleys (not shown in FIG. 187A) associated with the manual adjustment knob (229). Approximately 2 millimeters from the distal tip (237), a distal ring (231) is positioned to function similarly to the proximal ring (233), but for a distal control element which, in the depicted embodiment, preferably is looped from the one or more pulleys (not shown in FIG. 187A) comprising the control element interface assembly (147), which is configured to be servo-robotically actuated from an instrument driver to which it may be coupled. The looping configuration of the control elements preferably provides greater break strength, in the range of twice the break strength of a single strand of the same control element wire material under tension, because with the both-side-soldered (325) and looping configuration around the proximal (233) or distal (231) ring, as depicted in FIG. 187D, each of the two strands of the continuous control element is configured to share loads as separate tension elements. The portion approximately two inches proximal of the distal ring (231) is configured to have relatively high, yet controllable flexibility, as controlled by catheter member reinforcing structures or “ribs” discussed in reference to FIG. 187B.

[0365] Referring to FIG. 187B, a cross sectional view of a distal portion of the sheath embodiment (227) depicted in FIG. 187A is depicted. As shown in FIG. 187B, the assembly is created around a mandrel (243) which is removed after assembly, which has a rounded-cornered-square cross section having a maximum diameter (257) of approximately 158 mils. Several layers are formed over the mandrel (243), as described in reference to FIG. 187E, including an inner layer (249), a distal control element (239) liner set, a braided layer (251), structural rib elements (245), and an outer jacket layer (255). The structural rib elements (245) function like small beams integrated into the walls of the construct and are configured to resist homogeneous omnidirectional cantilevered bending of the distal end of the sheath.

[0366] Referring to FIG. 187C, a cross sectional view of a more proximal portion of the sheath embodiment (227) depicted in FIG. 187A is depicted. The same mandrel (243) is utilized to construct the proximal portion, over which an inner layer (249) is placed, followed by a liner (247) sets for each of the subsequently introduced proximal and distal control elements (241, 239), a braided layer (251), a second braided layer (254), and an outer jacket layer (253) different from the outer jacket layer (255) of the distal portion of the sheath embodiment (227).

[0367] Referring to FIG. 187E, one embodiment of a method of constructing the embodiment depicted in FIGS. 187A-187D is illustrated with illustrative steps “A” through “L”. The first step (“A”) comprises placing a nylon 12 jacket approximately 2-3 mils thick over the entire length (proximal and distal) of the mandrel. Next (“B”), polyimide tubes lined with PTFE are stuffed with rectangular mandrels 4 mil by 12 mil. These small mandrels are placeholders for the tension elements, to be installed later with the pertinent ring element to which they are pre-soldered. The polyimide, PTFE-lined, mandrels are heat shrink bonded to the nylon jacket, subsequent to which (“C”) the proximal portion (proximal to the approximately two-inch more flexible distal section) is braided with 1×3 mil rectangular wire at 75 ppi (picks per inch) diamond pattern; the braiding is loosened in pattern over the distal section to 60 ppi. Next (“C+”), the distal section is covered with a later-to-be-removed heat shrink tubing layer, subsequent to which (“D”), the entire length of the construct is braided again with the same wire at a 40 ppi rate. Next (“E”) a 3 mil thick nylon 12 jacket is applied over the proximal portion (proximal of the subsequent position of the proximal ring), and the structure is heat fused (“F”) through a vertical heat shrinking device. Next (“G”) the distal heat shrink (from step “C+”) is removed along with any materials over it, and the pre-soldered proximal ring with looped proximal control element installed (“H”) by pulling the small mandrels out and pushing/pulling the looped control element into the same positions, and subsequently encapsulating the proximal ring into place with a small cuff of nylon 12 material. Next (“I”) rectangular reinforcing ribs (approximately 0.016×0.40 inches) are heat tacked into place along the sides of the portion of the sheath approximately two inches proximal to the position of the distal ring, and subsequently (“J”) a low-durometer jacket, preferably 40d Pebax, is heat fused over the portion of the sheath distal to the proximal ring. Subsequently (“K”) the distal ring and associated tension elements are installed similar to the installation of the proximal ring and tension elements, and (“L”) a short (approximately 1-2 mm long) soft tip section, preferably 35 d, is heat welded to the distal end, followed by installation of a Luer assembly proximally, and final assembly instrument base, including exposure of the two looped control elements through the wall of the proximal portion of the catheter member, installation of termination balls, preferably by mechanical crimp, upon the proximal ends of the control elements, and winding about the pertinent pulleys of the control element interface assembly and manual-knob-driven proximal element pulley.

[0368] Referring to FIGS. 188A and 188B, isometric views of the sheath instrument base (259) assembly are depicted to illustrate that the distal control element loop (239) in the embodiment depicted in FIGS. 187A-E may be servorobotically driven through a control element interface assembly (147) configured to interface with an instrument driver interface socket (not shown), while the proximal control element loop (241) may be actuated with a worm screw mechanism associated with a manual tensioning knob (229). FIG. 188B depicts an exploded view of the assembly of FIG. 188A. With the top plate (267) removed from the sheath instrument base (259), where it is fastened with fasteners (269) such as screws when fully assembled, the work gear (261) coupled to the manual tensioning knob (229) and the associated control element drive gear (263) and associated control element pulley (265) is depicted. A track (266) is depicted, formed in the sheath instrument base (259), to provide a pathway for the proximal control element loop to exit the wall of the proximal catheter member and spool into the control element pulley (265).

[0369] Referring to FIGS. 189A-C, a guide instrument embodiment (275) configured to coaxially interface with the sheath instrument embodiment (227) described in reference to FIGS. 187A-188B is depicted. The working length (277) of the depicted guide instrument catheter member (90) is about 92 centimeters, the most distal 122 millimeters of which (273, 271) are significantly more flexible or bendable than the proximal portions. The very distal 2 mm (271) comprises a soft tapered distal tip of an even more plyable polymeric material. This embodiment of the guide instrument has four control elements fastened to a single distal ring (295) and configured to facilitate omnidirectional distal tip navigation from a proximal interface to a servorobotic instrument driver, such as those described above. A guide instrument base (141) and two associated control element interface assemblies (147) and axles (157) are depicted in a configuration similar to that described in reference to FIGS. 103.1-103.6. In another embodiment, the guide instrument base may comprise a configuration such as that depicted in FIG. 6 (48) and be configured for a four-interface-socket (44) instrument driver (16) configuration such as that depicted in FIG. 6.

[0370] Referring to FIG. 189B, a proximal cross section of the guide instrument catheter member (90) depicted in FIG. 189A is depicted. Starting with an approximately circular mandrel (279) with a diameter of approximately 8 French, an inner layer (281) of nylon may be formed, followed by a metal hypotube layer (283) friction fit onto the most proximal eight inches of the construct, the metal hypotube layer (283) being about 5 mils in thickness. A braid layer (285) is subsequently added, followed by a second braiding layer (291) into which small mandrels (289) and liners (287) are woven, followed by installation of an outer jacket (293). Other details regarding this construction are described in reference to FIG. 189C.

[0371] Referring to FIG. 189C, steps for constructing a guide instrument embodiment such as that (275) depicted in FIG. 189A are illustrated. Over an 8 French mandrel (“A”), a 113 ID 117 OD (mils) thin nylon 12 jacket is placed (“B”), then an approximately 8″ long 5 mil thick metal hypotube is fit over that proximally with a friction fit (“C”), then the entire length is braided with diamond pattern (same wire as with above sheath) at 70 ppi (“D”); then another braid layer is installed at 20 ppi into which is woven four 10 mil-ID, 12 mil-OD, PTFE-lined, polyimide tubes with 9.5 mil PTFE-coated mandrels inside (“E”); then (“F”) a distal control ring is installed with four pre-soldered (with gold/tin) control elements or loops of control elements—which are fed into the positions of the small mandrels as woven into the second layer of braid; then (“G”) a keying extrusion is placed proximally (not over the distal 122 mm) which has a circular inner lumen and substantially rectangular outer cross sectional shape for keying with a coaxially-positioned sheath lumen such as those depicted in FIGS. 187B and C, to prevent relative rotation between such sheath instrument and guide instrument when coaxially interfaced; the distal 122 mm section gets a 40 durometer pebax jacket (“H”); then (“I”) the distal ring is encapsulated with a nylon 12 cuff, a 35 durometer soft distal tip is installed, and (“J”) the entire construct is heat shrinked and pressed into a rectangular cross sectional mold to keep the keyed cross section in place (primarily proximally, about the region of the metal hypotube layer); then (“K”) the proximal pullwires are exposed for instrument base installation, a Luer assembly is added (“L”), and the proximal instrument base is installed (“M”). The final construct of the depicted embodiment has an ID of approximately 8 French and an OD of approximately 152 mils long axis, and 138 mils short axis.

[0372] Although both the guide and sheath instruments described in reference to FIGS. 187A-189B utilize braiding for added torquability and kink resistance, spiral winds or spine constructs, such as those described above in reference to FIGS. 25-32 may also be utilized or similar purpose.

[0373] Referring to FIGS. 190A-190C, various views of one embodiment of a dilator compatible with the guide and sheath instruments described in reference to FIGS. 187A-189C are depicted. The depicted dilator embodiment (297) may be created by placing a thin polyimide liner (301 in FIG. 190C), which may be coated on the interior, mandrel-facing, lumen with a lubricious surface such as PTFE, over a PTFE-coated mandrel (not shown), then butt-welding a relatively long section of relatively rigid polymeric material, such as 72 durometer Pebax, to a relatively short distal section (311 in FIG. 190A) of relatively flexible polymeric material, such as 45 durometer Pebax, to form a main tubular body (299) which is more flexible distally than proximally. Proximally a Luer assembly (305) and hemostasis valve (307) are installed. A small platinum/iridium radio-opaque marker band (303) is installed distally, adjacent to which a 9-degree tapered end is created with a glass mold for tissue dilation at the distal tip of the dilator instrument embodiment (297). The inner lumen (309) diameter at the distal tip is configured to be very close to the outer diameter of the needle for which the dilator is configured to be used, while the outer diameter of the dilator is configured to fit within the inner diameter of the guide instrument with which is it configured to be utilized. In other words, each of the needle, dilator, guide, and sheath instruments preferably are configured for coaxial interfacing during a procedure.

[0374] Referring to FIGS. 191A-191C, various views of one embodiment of a needle compatible with the guide, sheath, and dilator instruments described in reference to FIGS. 187A-190C are depicted, wherein a flexible section near the distal tip facilitates passage of the needle around tight turns within a constraining lumen. An instrument set comprising a coaxial coupling of a sheath instrument, a guide instrument, a dilator instrument, and a needle instrument such as those described herein may be utilized to conduct a trans-septal puncture, as described above in reference to FIGS. 163-167. Subsequently, the needle and dilator may be withdrawn, and an ablation or mapping catheter inserted down the working lumen of the guide catheter to conduct a robotically-controlled ablation or mapping procedure, as described above in reference to FIGS. 167-174, within the chambers of the heart.

[0375] At the heart of the needle embodiment (313) depicted in FIGS. 191A-C is an intermediate section (319) of greater flexibility positioned proximally adjacent the distal non-coring needle point (318) of the needle to enable the distal end (318, 320) of the needle to navigate around small radius of curvature turns more easily than a conventional needle without the highly flexible section (319). The distal end (318, 320) preferably is soldered with gold or platinum material to provide radio-opacity, thereby facilitating placement and positioning of the distal end (318, 320) during a procedure. Proximal of the highly flexible section (319), the proximal needle shaft (321) preferably comprises stainless steel, and may be coupled to a pin vise (317). Proximally a Luer assembly (315) is installed upon the proximal needle shaft (321).

[0376] Referring to FIGS. 191B and 191C, two embodiments of the distal end (318, 320) and highly flexible section (319) are depicted in close up cross sectional view. In both embodiments, to prevent kinking, a prefabricated construct of polyimide and wire (322), the wire embedded into the polyimide in a braided or spiral wound pattern, is placed over the highly flexible section (319). Proximal of the highly flexible section (319), both proximal shaft sections (321) preferably comprise stainless steel. In the embodiment of FIG. 191C, the distal section (320) comprises stainless steel, while the section in between the distal section (320) and proximal section (321) which lies at the center of the highly flexible section (319), also termed the flexible shaft portion (326), comprises nitinol. In the embodiment of FIG. 191C, the flexible shaft portion (326) and distal section (320) comprise the same nitinol tube member. The depicted junctions between nitinol tubing and stainless steel tubing preferably are held together with an adhesive (323) such as epoxy, as depicted in FIGS. 191B-C. The distal section of the embodiment depicted in FIG. 191C may be created by merely necking down the anti-kink metal-reinforced polyimide layer and creating a needle tip (318). With nitinol extending distally from the proximal section (321), the entire distal portion of the embodiment of FIG. 191C is highly flexible—facilitating tight turn radii through tortuous paths of constraining lumens such as catheters or vessels. The embodiment of FIG. 191C, also having a highly flexible section (319) due in part to a nitinol flexible shaft portion (326), has a less flexible distal end (318, 320), complements of the stainless steel material comprising it, which may be desirable when the more dramatic flexibility of the embodiment of FIG. 191C is not desired.

[0377] Many tools and sets of tools besides needles and dilators may be controllably delivered and actuated with the help of a guide, or guide+sheath instrument combination similar to those described in reference to the needle/dilator/guide/sheath instrument arrangement. For example, in another embodiment, a remotely-actuated grasper, such as those available from Intuitive Surgical, Inc., or described in U.S. patent application Ser. No. 10/011,371 to endoVia Medical, Inc., may be used in concert with a remotely steerable guide instrument system sized appropriately for the application. In another embodiment, a remotely steerable guide instrument system such as those described herein may be utilized to place a guidewire, inject with a needle gene or cell therapy into the heart wall, the parenchyma of an organ, etc. In another embodiment, a remotely steerable guide instrument system such as those described herein may be utilized to carry a camera and/or a radiation source (such as a light, or infrared source for cameras such as those available from CardioOptics, Inc.). In another embodiment, a remotely steerable guide instrument system such as those described herein may be utilized to carry a cryo-ablation system or laser ablation system to a precise location adjacent an organ, inside the heart, etc. In another embodiment, a remotely steerable guide instrument system such as those described herein may be utilized to place a pacing lead into the coronary sinus, or place a sensor within the heart or vessels for monitoring, for example, pressure within the left ventricle. Such pressure monitoring may be used, for example, to closely watch heart failure patients and adjust medicine, diuretics, fluid intake, etc. In another embodiment, a remotely steerable guide instrument system such as those described herein may be utilized to deploy an expandable or expanded medical device, such as a stent or stent graft, into a vessel or other lumen with a high degree of precision and visualization. In another embodiment, multiple remotely steerable guide instrument systems such as those described herein may be utilized in a procedure. For example, one guide instrument could be used for precisely positioning a camera and light source while another guide instrument could be used for precisely positioning an interventional instrument such as a grasper, ablation tool, injection needle, etc. Many tools may be utilized with the subject high-precision robotic catheter system, including but not limited to: Graspers, 2DOF articulating guidewires (roll+bend), biopsy forceps, high energy directed ultrasound probes, biopsy needles, lasers, aspiration needles, UV light sources, guides for pacing or other lead delivery, needles for drug delivery and biopsy, scissors, RF ablation probes/tools/needles, clamp and stitch tools, cryo ablation devices, pledget placement devices, ultrasound ablation tools, clip delivery tools, ultrasound tissue welding probes, flow transducers, RF tissue welding tools, and Pressure transducers.

[0378] While multiple embodiments and variations of the many aspects of the invention have been disclosed and described herein, such disclosure is provided for purposes of illustration only. Many combinations and permutations of the disclosed system are useful in minimally invasive surgery, and the system is configured to be flexible. For example, depending upon the medical application, it may be desirable to have a guide instrument with less than four control elements, combined with a sheath instrument, or perhaps combined with a prebent, unsteerable sheath, or perhaps with no sheath at all. The instrument driver may be tailored to match the instrument configuration, with less motors and gearboxes for less control elements, or variation in the configuration for actuating a given control element interface assembly, and associated variation in the tensioning mechanism and number of control element pulleys associated with the pertinent control element interface assembly (one pulley and one cable per control element interface assembly, two pulleys and two cables per control element interface assembly, slotted, split carriage, and winged split carriage embodiments, various tensioning embodiments, etc).