Systems and methods for positioning a catheter

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 61/027,710, filed Feb. 11, 2008, and entitled “Systems and Methods for Positioning a Catheter,” which is incorporated herein by reference in its entirety.

[0002] Briefly summarized, embodiments of the present invention are directed to a method for displaying a position of a medical device, such as a catheter, during insertion thereof into a patient.

[0003] In one example embodiment, the method includes obtaining a first set of detected position data relating to a location marker, then determining a possible first position of the location marker. A first confidence level relating to a match between the first set of detected position data and a first set of predicted position data is assigned. A determination is made whether the first confidence level meets or exceeds a first threshold. If the first confidence level meets or exceeds the first threshold, a determination is then made whether the first position of the location marker is within a first detection zone. If the first position of the location marker is within the first detection zone, the first position of the location marker is displayed.

[0004] These and other features of embodiments of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of embodiments of the invention as set forth hereinafter.

[0020] Reference will now be made to figures wherein like structures will be provided with like reference designations. It is understood that the drawings are diagrammatic and schematic representations of exemplary embodiments of the present invention, and are neither limiting nor necessarily drawn to scale.

[0021] FIGS. 1-12 depict various features of embodiments of the present invention, which is generally directed to methods and systems for detecting a location of a catheter, or of a catheter placement device, within a patient. Certain of such methods and systems relate more particularly to the detection and graphical representation of a location of a catheter or catheter placement device. In some embodiments, the systems and methods can represent the location relatively accurately and/or can reduce the number of erroneous identifications of the location, as further described below.

[0022] With reference to FIG. 1, in certain embodiments, a catheter 10 can be inserted in a vasculature 20 of a patient 25. The catheter 10 can be advanced in a distal direction from an entry point 28 to a destination 30, such as a target site or a desired or predetermined location within the patient 25. The catheter 10 can thus be advanced along a path 35 through the patient. In some embodiments, the catheter 10 can comprise a peripherally inserted central catheter (“PICC”), a central venous catheter (“CVC”), or another suitable catheter or medical device. In some embodiments, the destination 30 for a distal end 50 of the catheter 10 is within the superior vena cava (“SVC”). In other embodiments, the catheter 10 can be advanced to other suitable destinations 30 within the patient 25.

[0023] For clarity it is to be understood that the word “proximal” refers to a direction relatively closer to a clinician using the device to be described herein, while the word “distal” refers to a direction relatively further from the clinician. For example, the end of a catheter placed within the body of a patient is considered a distal end of the catheter, while the catheter end remaining outside the body is a proximal end of the catheter. Further, the words “including,” “has,” and “having,” as used herein, including the claims, shall have the same meaning as the word “comprising.”

[0024] In certain embodiments, the catheter 10 is operably associated with a location marker 40. The location marker 40 can be at the distal end 50 of the catheter 10, and in some embodiments, may be integrally formed therewith. The location marker 40 can comprise an energy emitter or field producer of any suitable variety, and can include one or more permanent magnets (e.g., rare earth magnets), electromagnetic coils, or other magnetized materials or structures. In yet other embodiments, the location marker can comprise ultrasonic emitters, electromagnetic field emitters, visible/infrared photon emitters, ionizing radiation emitters, etc.

[0025] In one embodiment, the location marker can be tracked using the teachings of one or more of the following U.S. Pat. Nos. 5,775,322; 5,879,297; 6,129,668; 6,216,028; and 6,263,230. The contents of the afore-mentioned U.S. patents are incorporated herein by reference in their entireties.

[0026] As mentioned, the location marker 40, when associated with the catheter 10 as described above, enables the distal end 50 of the catheter to be tracked during its advancement through the vasculature. The direction in which the catheter tip is pointing can also be ascertained, thus further assisting accurate catheter placement. The location marker 40 further assists the clinician in determining when a malposition of the catheter distal end 50 has occurred, such as in the case where the distal end has deviated from a desired venous path into another vein.

[0027] With reference to FIG. 2A, in some embodiments, the location marker 40 is included on a stylet 60. The stylet 60 can be preloaded into a lumen of the catheter 10 prior to advancing the catheter 10 through the vasculature 20 of the patient 25, and may extend substantially to the distal end 50 of the catheter 10 such that the location marker 40 is substantially co-terminal with the catheter distal end. In some embodiments, only a distal portion of the stylet 60 includes the location marker 40. For example, a discrete section of a distal portion of the stylet may include permanent magnetic materials. In other embodiments, a larger portion of the stylet can comprise permanent magnetic materials. In some embodiments, the stylet 60 is removed from the lumen of the catheter 10 once the distal end 50 of the catheter has been positioned at the destination 30.

[0028] In greater detail, the stylet 60 includes a proximal end 62 and a distal end 70. A handle 64 is included at the stylet proximal end 62, with a core wire 66 extending distally therefrom. A magnetic assembly of magnetic elements that form the location marker 40 in the present embodiment is disposed distally of the core wire 66. The magnetic assembly includes the one or more magnetic materials disposed adjacent one another proximate the stylet distal end 70 and encapsulated by tubing 68. In the present embodiment, a plurality of permanent magnetic elements is included, each element including a solid, cylindrically shaped ferromagnetic stacked end-to-end with the other magnetic elements. An adhesive tip 69 can fill the distal tip of the tubing 68 adjacent the magnetic elements of the location marker 40. This configuration is exemplary; other location marker configurations are also contemplated.

[0029] Note that in other embodiments, the magnetic elements described above may vary from the design in not only shape, but also composition, number, size, magnetic type, and position in the stylet, guidewire, etc. For example, in one embodiment, the plurality of ferromagnetic magnetic elements is replaced with an electromagnetic assembly, such as an electromagnetic coil, which produces an electromagnetic field for detection by the sensor. Another example of an assembly usable here can be found in U.S. Pat. No. 5,099,845 entitled “Medical Instrument Location Means,” which is incorporated herein by reference in its entirety. Yet other examples of stylets including magnetic elements that can be employed with the catheter tip location modality described herein can be found in U.S. application Ser. No. 11/466,602 filed Aug. 23, 2006, and entitled “Stylet Apparatuses And Methods Of Manufacture,” published as U.S. Publication No. 2007-0049846 which is incorporated herein by reference in its entirety. These and other variations are therefore contemplated by embodiments of the present invention. It should be appreciated herein that “stylet” as used herein can include any one of a variety of devices configured for removable placement within a lumen of the catheter to assist in placing a distal end of the catheter in a desired location within the patient's vasculature.

[0030] With reference to FIG. 2B, in another embodiment, the location marker 40 including a plurality of magnetic elements or other suitable structure is included on a distal portion of the guidewire 80 proximate a distal end 90 thereof. In this embodiment, the distal tip 90 of the guidewire 80 is advanced to the destination 30 within the patient 25. The catheter 10 can then be advanced over the guidewire 80 until the distal end 50 of the catheter 10 is at the destination 30. The guidewire 80 can then be removed from the patient 25.

[0031] FIG. 2C gives various details regarding a distal portion of a stylet 92 including the location marker 40 configured in accordance with one possible embodiment. A coil assembly 96 is included proximate a stylet distal end 94 and is operably connected to leads 96A. The leads 96A are in turn operably connected to corresponding circuitry in a tip location system (FIG. 10) configured to produce an electric pulse signal so as to enable the coil assembly 96 to be electrically pulsed during operation and produce an electromagnetic field having a predetermined frequency or pattern that is detectable by one or more sensors included in a detector placed proximate to the patient 25 (FIG. 3) during transit of the catheter through the vasculature when the coil assembly is within the detectable range of the sensor. Note that the coil assembly described herein is but one example of a field-producing element, or a component capable of producing an electromagnetic field for detection by the sensor. Indeed, other devices and assembly designs can be utilized here to produce the same or similar functionality.

[0032] The coil assembly 96 and leads 96A are disposed within tubing 98 that extends the length of the stylet 92. The coil assembly and leads can be protected in other ways as well. A core wire 99 can be included within the tubing 98 in one embodiment to offer stiffness and/or directional torqueability to the stylet 92. The core wire 99 in one embodiment includes nitinol and can extend to the distal end 94 of the stylet 92 or terminate proximal thereto.

[0033] With reference to FIG. 3, in certain embodiments, a tip location detector 100 is positioned adjacent or proximate to the patient 25 as the catheter 10 is advanced to the destination 30 within the patient vasculature. For example, in the illustrated embodiment, the detector 100 can be positioned on the chest of the patient 25.

[0034] The detector 100 includes in the present embodiment one or more sensors 110. Two sensors 110 are shown schematically in the illustrated embodiment. In some embodiments, the location detector 100 can include one or more, two or more, etc. sensors 110. For instance, in one embodiment, the detector 100 includes ten sensors 110 placed in a spaced-apart configuration within the detector body. The sensors 110 are configured to detect the location marker 40. For example, each sensor 110 can be configured to detect the strength of a magnetic field produced by the location marker 40 at the position of the sensor 110 and by so doing enable the system to calculate an approximate location and orientation of the location marker.

[0035] In some embodiments, the detector 100 defines one or more branches 120. In some embodiments, two branches 120a, 120b of the detector 100 extend upward and outward from a lower branch 120c such that the detector 100 is substantially “Y”-shaped. Terms such as “upper” and “lower” are used herein by way of convenience, and not limitation, to describe the embodiments depicted in the figures. Accordingly, the upper branches 120a, 120b are closer to the head of the patient 25 than is the lower branch 120c.

[0036] FIG. 3 illustrates an axis convention that will be used throughout the remainder of this disclosure by way of convenience and not limitation. In the illustrated embodiment, three dimensional Cartesian coordinate system is centered on the lower branch 120c of the detector 100. The positive portion of the X-axis runs toward the right of the page (i.e., toward the left side of the patient 25), the positive portion of the Y-axis runs toward the top of the page (i.e., toward the head of the patient 25), and the positive portion of the Z-axis extends directly out of the page (i.e., away from the chest of the patient 25). Accordingly, the portion of the Z-axis extends through the patient 25 such that a more negative Z-value is deeper within the patient relative to the detector 100.

[0037] In some embodiments, a portion of the detector 100 can be expected to be more sensitive to the initial detection of the location marker 40 than other portions of the detector 100. For example, in some embodiments, the location marker 40 may be expected to pass beneath (i.e., below, relative to the Z-axis) the branch 120a of the detector 100 before passing beneath other portions of the detector 100 as the catheter 10 is advanced toward the superior vena cava of the patient 25. In some embodiments, data processing algorithms based on such an expectation can be used to reduce or eliminate misidentification of a position of the location marker 40 or “false positive” identifications that represent something other than the marker 40.

[0038] With reference to FIG. 4, in some embodiments, the detector 100 is in communication with a processor 130. The processor 130 can comprise any suitable storage and/or computing device, such as, for example, a computer configured to run one or more programs, or a microprocessor. The processor 130 can be configured to receive data obtained by the detector 100 (e.g., via the sensors 110) and to process the data to determine a position of the location marker 40, as further described below. In some embodiments, the processor 130 utilizes detection zones in processing the data received from the detector 100 and/or in delivering a representation of the position of the location marker 40 for display. One possible environment in which the processor 130 is included is seen in FIG. 10, as described further below.

[0039] In some embodiments, the processor 130 utilizes a first detection zone 140 and a second detection zone 150. In some embodiments, the first detection zone 140 encompasses a relatively large portion of the upper branches 120a, 120b of the detector 100. For example, in some embodiments, the first detection zone 140 extends from a base portion of each branch 120a, 120b to a position above the detector 100 in the positive Y direction, beyond the detector 100 in both the positive and negative X directions, and below the detector 100 in the negative Z direction. As such, the first detection zone 140 and second detection zone 150 define imaginary rectangular volumes of space proximate the detector 100 that extend into the body of the patient 25. In one embodiment, for example, the size of the first detection zone 140 is about 28 centimeters (cm) in the X direction, about 10.5 cm in the Y direction, and about 8 cm in the Z direction. The size of the second detection zone 150 is about 23 cm in the X direction, about 15 cm in the Y direction, and about 11 cm in the Z direction. Other detection zone dimensions are also possible.

[0040] In other embodiments, the first detection zone 140 does not include the detector 100. For example, in some embodiments, the first detection zone 140 can be substantially as shown in FIG. 4, but begins at a position below the detector 100 (i.e., at a position in the negative Z direction), and extends toward more negative Z-values.

[0041] One or more of the first and second detection zones 140, 150 can include a portion of the path 35 along which the catheter 10 is advanced. In some embodiments, the first detection zone 140 includes a portion of the path 35 that is proximal of a portion of the path 35 that runs through the second detection zone 150. In other embodiments, only the first detection zone 140 may include a portion of the path 35.

[0042] In some embodiments, the first and second detection zones 140, 150 can overlap each other. For example, in the illustrated embodiment, the second detection zone 150 includes a portion of the upper branches 120a, 120b that is also included in the first detection zone 140. The first and second detection zones 140, 150 can define the same or different areas in any of the XY-, YZ-, or ZX-planes and can define the same or different volumes.

[0043] More or fewer detection zones are possible. Additionally, detection zones can define a variety of shapes, such as, for example, boxes, spheres, ellipsoids, and paraboloids. Detection zones may be suitably described in a variety of coordinate systems, such as, for example, Cartesian or polar coordinates.

[0044] FIG. 5 illustrates another embodiment of a detector 100 having an upper detection zone 160 and a lower detection zone 170 superimposed thereon. FIG. 5 provides approximate dimensions and approximate relative positions of the upper and lower detection zones 160, 170. In the illustrated embodiment, the detection zones 160, 170 begin at a position of about −1 centimeter from the origin of the Z-axis and terminate at a position of about −6 cm from the origin of the Z-axis.

[0045] Other dimensions than those illustrated in the instant embodiment are also possible. For example, one or more of the upper and lower detection zones 160, 170 can extend from about −1 centimeter to about −25 centimeters, from about −1 centimeter to about =15 centimeters, from about −1 centimeter to about −12 centimeters, or from about −1 centimeter to about −9 centimeters from the Z-origin. In some embodiments, the upper limit of the depth of one or more of the upper and lower detection zones 160, 170 can be within a range of between about 0 centimeters and −5 centimeters, and the lower limit of the depth of one or more of the first and second detection zones 160, 170 can be within a range of between about −5 centimeters and about −30 centimeters. Other ranges for the upper and lower detection zones 160, 170 are possible. The first and second detection zones 140, 150 can be defined in one embodiment by the same or different dimensions as the upper and lower detection zones 160, 170.

[0046] FIG. 6 depicts a catheter 10 having the location marker 40 positioned beneath the detector 100 of FIG. 4. A magnetic field produced by the location marker 40 is schematically illustrated by concentric circles. In the illustrated embodiment, the location marker 40 is within the first detection zone 140.

[0047] With reference to FIG. 7, in certain embodiments, the processor 130 can be in communication with a display device 200, such as, for example a graphical user interface on a screen (see also FIG. 10). In some embodiments, the display 200 includes a detector representation 210, which can depict a projection of the detector 100 in the XY-plane. A depth indicator 220 can depict a Z-coordinate of the location marker 40.

[0048] As shown in FIG. 8, in some embodiments, the display 200 can include a marker symbol 230 that represents a position of the location marker 40 relative to the detector 100 (compare FIG. 6), such as within a portion of the vasculature of the patient when the detector is positioned on the patient's chest. The marker symbol 230 can also indicate a direction in which the location marker 40 is moving or the direction that the location marker 40 is facing. For instance, in the view shown in FIG. 8, the location marker 40 indicates that the catheter 10 is generally advancing from the left side of the page toward the right side thereof. As further discussed below, in some embodiments, whether or not the marker symbol 230 is displayed and/or the position on the display 200 at which the marker symbol 230 is displayed is based on information received from the processor 130.

[0049] In some embodiments, the display 200 can include button icons 240 that correspond to buttons or controls located on a button control interface included in a console (FIG. 10) in which the display 200 is housed. Further informational or control icons 250 can be included on the display 200. In further embodiments, the display 200 comprises a touch screen such that a user can deliver instructions to the processor 130 and/or the tip location detector 100 via the buttons or controls appearing on the screen. Other systems and methods for providing instructions to the processor 130 and/or the tip location detector 100 are also possible.

[0050] With reference to FIG. 9, in certain embodiments, a tip location system 300 can include the detector 100, the processor 130, and/or the display 200. The system 300 can be configured to detect the location marker 40 and to display the marker symbol 230, as described above. In some embodiments, the detector 100 is positioned relative to the patient 25. The system 300 is then zeroed to calibrate to (or account for) local magnetic fields. In some embodiments, after the system 300 has been zeroed, the system 300 actively measures magnetic fields. For example, in an implementation where the location marker 40 includes a plurality of magnetic elements positioned at the distal end 70 of a stylet 60 pre-loaded in the catheter 10 (see the stylet 60 shown in FIG. 2A), the detector 100 can monitor or measure magnetic fields via the sensors 110 during transit of the catheter through the vasculature of the patient. The measurements can be obtained continuously, for example, or iteratively at regular or irregular intervals as determined by the processor 130 or other suitable control component of the system 300.

[0051] In some embodiments, a model 310 of the location marker 40 is stored in the system 300. For example, in some embodiments, the model 310 is stored in a memory portion of the processor 130 for access when needed. The model 310 can comprise magnetic strength patterns that are each representative of a magnetic field produced by the location marker 40 at one of a multitude of possible marker locations. In some embodiments, the processor 300 compares data received from the detector 100, which data relate to the position of the location marker 40 with respect to one or more of the detector sensors 110, with the model 310 to ultimately determine whether the location marker 40 is within one or more of the detection zones 140, 150.

[0052] In some embodiments, the processor 130 can execute a program or set of executable instructions that implements one or more algorithms for determining how well a data set of a possible location marker position gathered by the detector 100 corresponds with the model 310. The program can provide a confidence level regarding the data set. In some embodiments, the confidence level indicates how well such a data set and the model 310 match. In further embodiments, the confidence level indicates the degree of certainty that the location marker 40 is at a specific position. In still further embodiments, the confidence level represents how well a gathered data set and the model 310 match as well as the degree of certainty that the location marker 40 is at a specific position. The confidence level can be expressed as an absolute or a scalar value, in some embodiments. An example of a program that is suitable for use with certain embodiments described herein is software marketed under the trademark ZAP™, which is distributed by Lucent Medical Systems.

[0053] In certain embodiments, the processor 130 provides instructions to depict the marker symbol 230 (FIG. 8) corresponding to the detected position of the location marker 40 on the display 200 when certain conditions are met. For example, in some embodiments, after the system 300 has been zeroed or calibrated, in order for the display to initially depict the marker symbol 230, the center of the location marker 40 must be identified as being within the first detection zone 140 with a confidence level above a first threshold value (or with a confidence level within a first range). For example, in certain embodiments that use ZAP™ software, the center of the location marker 40 must be identified as being within the first detection zone 140 (which can, for example, be at a depth of between about 1 centimeter and about 8 centimeters below the detector 100), with a COST of less than or equal to 500. COST is a term associated with ZAP™ software that represents in one embodiment an absolute value of a comparative match between measured magnetic field data as detected by the detector 100 and predicted magnetic field data as computed by the processor 130. The COST value is on a reverse scale such that a lower value represents a relatively higher threshold value or level of confidence.

[0054] In some embodiments, multiple identification and validation sequences, or solution sequences, regarding a position of a possible location marker 40 are performed before the marker symbol 230 is initially displayed. For example, in some embodiments, the conditions relating to resolution of the possible location marker position with respect to the first and/or second detection zones 140, 150 and determination of a confidence level described in the preceding paragraph must be satisfied in eight consecutive sequences before the marker symbol 230 will initially be displayed. In other embodiments, the conditions must be met in five consecutive sequences before an initial display of the marker symbol 230. In certain of such embodiments, subsequent cycles may aid in pinpointing or converging on a more accurate location of the marker symbol 230, such that the marker symbol 230 may drift slightly after it is initially displayed. Other series of solution sequences are also possible.

[0055] After the initial display of the marker symbol 230, separate conditions may be implemented in order to continue displaying the maker symbol 230 after it has met the conditions to be displayed initially. For example in some embodiments, the marker symbol 230 will continue to be displayed if the center of the location marker 40 is within either the first detection zone 140 or the second detection zone 150 and if the confidence level is above a second threshold value (or within a second confidence range). In some embodiments, the second threshold value is lower then the first threshold value (i.e., the second threshold value can represent a lesser degree of confidence than does the first threshold value). For example, in certain embodiments that use ZAP™ software, the center of the location marker 40 must be identified as being within the first or second detection zones 140, 150 with a COST of less than or equal to 1000 in order for the marker symbol 230 to continue to be displayed.

[0056] In further embodiments, the first and second detection zones 140, 150 can be expanded in size after the initial identification of the location marker 40 and initial display of the marker symbol 230. For example, in some embodiments, the first and second detection zones 140, 150 extend between a depth of about 1 centimeter and about 8 centimeters below the detector 100 before the initial display of the marker symbol 230, and can extend between a depth of about 1 centimeter and about 12 centimeters below the detector after the initial display of the marker symbol 230. Of course, modification of the detection zone sizes in amounts different from those outlined above is also possible.

[0057] An initial display of the marker symbol 230 can occur after events other than or in addition to zeroing the system 300. For example, in some embodiments, the system 300 may be turned off after having displayed the marker symbol 230. Upon being turned on again, a subsequent showing of the marker symbol 230 can be referred to as an initial display of the marker symbol 230. In other embodiments, the system 300 can be reset without powering down such that a first display of the marker symbol 230 after the resetting event would be an initial display of the marker symbol 230.

[0058] In some embodiments, the system 300 can employ separate criteria for displaying the marker symbol 230 after the system 300 has tracked the position of the location marker 40, e.g., after initially displaying and continuing to display the marker symbol 230. For example, in some embodiments, if the location marker 40 is moved out of the sensing range of the detector 100, e.g., outside of the first and second detection zones 140, 150 and subsequently moved back into the sensing range, the tracking can start again if the detector 100 senses that the location marker 40 is within the first detection zone 140 or the second detection zone 150 and is above the first threshold value, e.g., COST is less than or equal to 500. Similarly, in some embodiments, if the system 300 loses the tracking of the location marker 40, e.g., fails to identify the position of the location marker 40 during a solution sequence, the tracking can commence again if the detector 100 senses that the location marker 40 is within the first detection zone 140 or the second detection zone 150 and is above the first threshold value.

[0059] In some embodiments, the system 300 may be preset such that the threshold values are fixed. In other embodiments, the system 300 can be altered by a user to vary one or more threshold values, as desired.

[0060] FIG. 10 depicts in simplified form an example implementation of a tip location system, i.e., the system 300 partially depicted in FIG. 9, in which embodiments of the present invention can be practiced. As shown, the system 300 generally includes a console 420, display 200, probe 440, and detector 100, each of which is described in further detail below. As mentioned above, the system 300 is employed to ultimately position a distal end 50 of the catheter 10 in a desired position within the patient vasculature. In one embodiment, the desired position for the catheter distal end 50 is proximate the patient's heart, such as in the lower one-third (⅓^rd) portion of the SVC (FIG. 1). Of course, the system 300 can be employed to place the catheter distal end in other locations.

[0061] A processor 422, including non-volatile memory such as EEPROM for instance, is included in the console 420 for controlling system function during operation of the system 300, thus acting as a control processor. A digital controller/analog interface 424 is also included with the console 420 and is in communication with both the processor 422 and other system components to govern interfacing between the probe 440, detector 100, and other system components.

[0062] The system 300 further includes ports 452 for connection with the detector 100 and optional components 454 including a printer, storage media, keyboard, etc. The ports in one embodiment are USB ports, though other port types or a combination of port types can be used for this and the other interfaces connections described herein. A power connection 456 is included with the console 420 to enable operable connection to an external power supply 458. An internal battery 460 can also be employed, either with or exclusive of an external power supply. Power management circuitry 459 is included with the digital controller/analog interface 424 of the console to regulate power use and distribution.

[0063] The display 200 in the present embodiment is an LCD-based device, is integrated into the console 420, and is used to display information to the clinician during the catheter placement procedure. In another embodiment, the display may be separate from the console. In one embodiment, the console button interface 432 (FIGS. 1, 8C) and buttons included on the probe 440 can be used to control the display 200 and thus assist the clinician during the placement procedure.

[0064] In one embodiment the system 300 optionally includes the probe 40, which is employed in connection with ultrasound (“US”)-based visualization of a vessel, such as a vein, in preparation for insertion of the catheter 10 into the vasculature. Such visualization gives real time ultrasound guidance for initially introducing the catheter into the vasculature of the patient and assists in reducing complications typically associated with such introduction, including inadvertent arterial puncture, hematoma, pneumothorax, etc. After the catheter has been initially placed in the patient vasculature, the system 300 can be used to locate the distal end 50 of the catheter 10 via detection of a corresponding location marker, as has been described above. In one embodiment, another modality can be added to the system 300, wherein an ECG-based confirmation of correct catheter distal tip placement with respect to a node of the patient's heart is employed. Further details regarding the US, tip location, and ECG-based modalities of the system 300 can be found in U.S. application Ser. No. 12/323,273, filed Nov. 25, 2008, and entitled “INTEGRATED SYSTEM FOR INTRAVASCULAR PLACEMENT OF A CATHETER,” published as U.S. Publication No. 2009-0156926 which is incorporated herein by reference in its entirety.

[0065] FIG. 10 shows that the probe 440 further includes button and memory controller 442 for governing button and probe operation. The button and memory controller 442 can include non-volatile memory, such as EEPROM, in one embodiment. The button and memory controller 442 is in operable communication with a probe interface 444 of the console 420, which includes a piezo input/output component 444A for interfacing with a piezoelectric array included in the probe, and a button and memory input/output component 444B for interfacing with the button and memory controller 442.

[0066] Embodiments of the present invention may comprise a special purpose or general-purpose computer including computer hardware. Embodiments within the scope of the present invention also include computer-readable media for carrying or having computer-executable instructions or data structures stored thereon. Such computer-readable media can be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, computer-readable media can include physical (or recordable-type) computer-readable storage media, such as, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, non-volatile and flash memory, or any other medium which can be used to store desired program code means in the form of computer-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer.

[0067] In this description and in the following claims, a “network” is defined as one or more data links that enable the transport of electronic data between computer systems and/or modules. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a computer, the computer properly views the connection as a computer-readable medium. Thus, by way of example, and not limitation, computer-readable media can also include a network or data links which can be used to carry or store desired program code means in the form of computer-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer.

[0068] Computer-executable instructions comprise, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. The computer executable instructions may be, for example, binaries, intermediate format instructions such as assembly language, or even source code. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the described features or acts described above. Rather, the described features and acts are disclosed as example forms of implementing the claims.

[0069] Those skilled in the art will appreciate that the embodiments of the present invention may be practiced in computing environments with one or more types of computer system configurations, including, personal computers, desktop computers, laptop computers, message processors, hand-held devices, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, mobile telephones, PDAs, pagers, and the like. Embodiments may also be practiced in distributed system environments where local and remote computer systems, which are linked (either by hardwired data links, wireless data links, or by a combination of hardwired and wireless data links) through a network, both perform tasks. In a distributed system environment, program modules may be located in both local and remote memory storage devices.

[0070] Thus, in one embodiment, and as depicted in FIG. 11, a method 500 for displaying a position of a medical device includes calibrating the system 300 at stage 510. At stage 520, a first set of detected position data relating to a possible first position of a location marker is obtained. As has been described, the position data can relate to an X-Y-Z-coordinate on a Cartesian coordinate axis grid centered on or proximate to the detector 100, as shown in FIG. 4. In the present embodiment, the position data includes data from the magnetic field produced by the magnetic assembly of the location marker of the stylet as sensed by each of the sensors 110 of the detector 100. These data are forwarded to the processor 130 of the system 300.

[0071] At stage 525, the possible first position of the location marker is determined. In one embodiment, the possible first position relates to the initial detection of the location marker by the system and is estimated by a neural net functionality provided by the processor 130 or other suitable component of the system. In brief, the neural net functionality continually monitors detected position data and provides a best guess of the position of the location marker. In the present embodiment, the neural net functionality is pre-programmed, or “trained,” with sample location marker position data, i.e., magnetic field data, for a variety of possible location marker positions and orientations with respect to the detector 100. This training enables the neural net to make a best fit determination between its pre-programmed sample position data and the detected position data obtained in stage 520 to determine a possible first position of the location marker. Determination of the possible first position of the location marker in this stage is made in the present embodiment by the processor 130 or other suitable component via execution of the ZAP™ Software.

[0072] At stage 530, a first confidence level relating to a match between the first set of detected position data and a first set of predicted position data relating to the possible first position of the location marker is assigned. The predicted position data in the present embodiment is provided by the processor 130 or other suitable component via execution of the ZAP™ Software, which calculates the predicted data based on physics-based characteristics of the location marker (in the present embodiment, a stack of magnetic elements as seen in FIG. 2A) assumed to be positioned at the possible first position. The resulting first set of predicted position data includes data for each sensor of the detector on the chest of the patient and is compared to the corresponding first set of detected position data for each sensor. This comparison yields the first confidence level, which is a quantitative, absolute value indicating the degree of matching between the detected data obtained at stage 520 and the predicted data. As has been discussed above, the COST value produced by the ZAP™ Software is one example of a confidence level that can be employed in the present method 500. Again, further details regarding the ZAP™ Software and the COST value are given in one or more of U.S. Pat. Nos. 5,775,322, 5,879,297, 6,129,668, 6,216,028, and 6,263,230, each of which is incorporated herein by reference in its entirety. Of course, other algorithms utilizing other confidence level configurations can also be used.

[0073] In one embodiment, stages 525 and 530 above are iteratively executed in order to better pinpoint the possible first position of the location marker. With each iteration, the possible first position is modified, which in turn modifies the set of predicted position data, in the interest of better matching the predicted data with the detected position data obtained at stage 520. This in turn increases the first confidence level, i.e., reduces the COST value in the present embodiment where the ZAP™ Software is employed. Such an iterative method is also referred to as a convergence algorithm. Once a minimum COST value is obtained via the convergence algorithm, the method can proceed. In other embodiments, a predefined number of iterations can be performed; in still other embodiments no additional iterations are performed.

[0074] At stage 540, it is determined whether the first confidence level meets or exceeds a first threshold, such as a predetermined COST value in the present embodiment, as described further above. As described above, the present stage, as well as stages 525 and 530, is executed in the present embodiment by the ZAP™ Software, or other suitable algorithm. If the first confidence level fails to meet or exceed the first threshold, such as a COST value of 500 in one embodiment, the possible location marker is not displayed and the method cycles back to stage 520 to continue monitoring for the presence of a possible location marker.

[0075] If the first confidence level meets or exceeds the first threshold, however, stage 550 is executed, wherein it is determined whether the first position of the possible location marker is within a first detection zone, such as the first detection zone 140 shown in FIG. 4. This stage is executed in one embodiment by the processor 130 of the system 300, as shown in FIG. 10. If the first position is not within the first detection zone, the possible location marker is not displayed and the method cycles back to stage 520 to continue monitoring for the presence of a possible location marker. If the first position is within the first detection zone, however, stage 560 is executed, wherein the first position of the location marker is displayed, such as on the display 200 shown in FIGS. 8 and 10, for instance.

[0076] In one embodiment, stages 520 through 550 are repeated in sequence a predetermined number of times before stage 560 is executed and the location marker is displayed. In one embodiment, stages 520 through 550 are successfully executed eight times, after which the location marker is displayed. Of course, the number of iterations can vary.

[0077] Reference is now made to FIG. 12. In one embodiment, the method for displaying the position of a medical device can continue after display of the first position of the location marker at stage 560 such that further advancement of the location marker 40 associated with the medical device, such as the catheter 10 progressing through a vasculature, can be progressively displayed. At stage 570, a second set of detected position data relating to a possible second position of the location marker is obtained.

[0078] At stage 575, the possible second position of the location marker is determined. In the present embodiment, the possible second position relates to the first position of the location marker, and as such no best fit guessing by a neural net component of the ZAP™ Software or other suitable algorithm need be performed.

[0079] At stage 580, a second confidence level relating to a match between the second set of detected position data and a second set of predicted position data, is assigned. As was the case with stages 525 and 530 of FIG. 11, stages 575 and 580 can be iteratively performed in the present embodiment in order to find a minimum COST value. In other embodiments, a predetermined number of iterations, or no iterations, can be performed.

[0080] At stage 590, it is determined whether the second confidence level meets or exceeds a second threshold, such as a predetermined COST value in the present embodiment, as described further above. As has been described, the second threshold in one embodiment is relatively lower, i.e., the COST value is higher, than the first threshold. In the present embodiment, the COST value is 1000, for instance. If the second confidence level fails to meet or exceed the second threshold, the possible location marker is not displayed and the method can cycle back to stage 570 to continue monitoring for further location marker position data.

[0081] If the second confidence level meets or exceeds the second threshold, however, stage 600 is executed, wherein it is determined whether the second position of the location marker is within at least one of the first and second detection zones, such as the first detection zone 140 and second detection zone 150 shown in FIG. 4. If not, the possible location marker is not displayed and the method can cycle back to stage 570 to continue monitoring for further location marker position data. If the second position is within the first detection zone and/or the second detection zone, however, stage 610 is executed, wherein the second position of the location marker is displayed.

[0082] In one embodiment, stages 570 through 600 are repeated in sequence a predetermined number of times before stage 610 is executed and the location marker is displayed. In another embodiment, no repetitions of the sequence are performed before display at stage 610 is executed.

[0083] In one embodiment, stage 580 includes ensuring that the second position of the location marker is within a predetermined distance range from the first position of the location marker within a predetermined amount of time so as to prevent maverick detection of non-location marker targets from being validated as location markers. It is noted that one or more of stages 570-610 of the method 500 can be successively repeated to find and display additional positions of the location marker during advancement of the catheter 10 through the patient's vasculature.

[0084] Embodiments of the invention may be embodied in other specific forms without departing from the spirit of the present disclosure. The described embodiments are to be considered in all respects only as illustrative, not restrictive. The scope of the embodiments is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.