Fluoroscopically Alignable Cutter Assembly and Method of Using the Same

The present invention relates to an assembly, generally a cutter assembly, more specifically to a fluoroscopically alignable cutter assembly, of the type that is insertable in a body vessel, orifice or conduit such as the urethra.

Catheters are used to insert cutting elements in body vessels, orifices, or conduits, such as arteries narrowed by atherosclerotic plaque and/or fibromuscular disease or to perform surgery within a constricted or obstructed ureter or urethra. Often, such catheters are of a dilation nature and serve to dilate the body vessels, orifices, and conduits. They basically consist of an elongated catheter, having an inflatable balloon or bladder at or near its distal end. A guide wire or other axial support means is often included to improve the torque control or "steerability" of the apparatus.

When a cutter assembly is inserted in the body vessel, orifice, or conduit, the cutting element carried by the cutting assembly must be properly aligned so that the cut made into the tissue or plaque is properly oriented. This is particularly important when the cutting element is carried by a dilation catheter and when the tissue is stressed and thereby subjected to significant trauma as it is cut by the cutting element. It would be highly undesirable if a cut was propagated in an undesirable direction since this might cause significant nerve and/or muscle damage. Fluoroscopy can be used to observe the cutter assembly as it is inserted into the patient. However, in many instances, for example, in prostate surgery, the fluoroscopic picture is a picture which looks downwardly upon the cutter assembly and the generally radiopaque cutting element, but does not readily show the precise orientation of the cutting element. Basically the cutting element shows up as a thin line under fluoroscopy and the precise orientation of the thin line is not readily apparent.

Radiopaque markings have been used to indicate the longitudinal positioning of balloons in body conduits. However, they have not been used to indicate angular orientation of such balloons (since balloons are generally radially symmetrical) nor have such markings been used to angularly orient cutters or the like in body conduits.

While the present invention is primarily contemplated as being useful with cutting elements it should be realized that it is more broadly useful with any device which is insertable in the body and which does not operate symmetrically but is instead sensitive to angular alignment about its longitudinal axis.

The present invention is directed to overcoming one or more of the problems as set forth above.

In accordance with an embodiment of the present invention, a fluoroscopically alignable assembly is set forth. The assembly comprises a longitudinally extending support having distal and proximal end portions and a longitudinal axis and being extendable into a body cavity. A radiopaque element is supported by the support in such a manner that rotation of the support about the axis changes the orientation of the element relative to the support. A radiopaque marker pattern is carried by the support, the pattern being such that by fluoroscopic viewing of the pattern a user can determine the orientation of the element about the axis.

In accordance with another embodiment of the present invention, a method is set forth of fluoroscopically aligning an assembly. The assembly, which is as set forth above, is inserted into a body vessel, orifice, or conduit. A fluoroscopic image of the assembly is detected. The position of the cutting is adjusted relative to the radiopaque marker pattern so as to align the element in a desired orientation for incising the body vessel, orifice, or conduit.

In accordance with still another embodiment of the invention tissue defining a body cavity is incised in a desired rotational orientation or orientations by aligning a cutting element as set forth above and then performing the incising.

The present invention allows one to readily align an element, for example, a cutting element, which is within a body vessel, orifice, or conduit whereby the cutting occurs in a desired direction. In accordance with an embodiment of the present invention, the length of the cutting element is also made visible due to the radiopaque marker pattern whereby both the angular orientation and the longitudinal position of cutting within the body vessel, orifice, or conduit can be readily controlled by the surgeon.

The invention will be better understood by reference to the figures of the drawings wherein like numbers denote like parts throughout and wherein:

FIG. 1 is a partial perspective view of a cutter assembly in accordance with an embodiment of the present invention;

FIG. 2 is a side elevation view of an alternative embodiment of the cutter assembly in accordance with an alternate embodiment of the present invention;

FIG. 3 is a section view taken along the line 3--3 of FIG. 2;

FIG. 4 is a view similar to FIG. 1, showing an alternate embodiment in accordance with the present invention;

FIG. 5 is a partial top elevation view of a section of a cutter assembly in accordance with yet another embodiment of the present invention; and

FIG. 6A is a radial view of the cutter assembly in FIG. 5, showing one step in an alignment procedure of the present invention; and

Adverting to FIG. 1, a fluoroscopically alignable assembly, in the embodiment illustrated a cutter assembly 10, is shown which is in accordance with an embodiment of the present invention. The assembly 10 includes a longitudinally extending cutting element support 12, having a distal end portion 14 and a proximal end portion 17 and being extendable into a body cavity, orifice or conduit (not shown). A cutting element 18, which is generally itself radiopaque, is supported by the cutting element support 12. In the particular embodiment of FIG. 1, a balloon or bladder 20 is supported by the cutting element support 12 and the cutting element 18 is supported by the balloon 20. Such an assembly is described in more detail in co-pending applications, Ser. Nos. 07/522,254, now U.S. Pat. No. 5,080,660, filed concurrently herewith, and 07/298,477, filed Jan. 18, 1989, now abandoned and the disclosures therein are incorporated herein by reference thereto. A number of cutting elements 18 can be utilized in accordance with the present invention. However, the present invention is particularly useful when the cutting element is of the nature of a radio frequency electrosurgical cutting wire of the type described in the aforementioned co-pending U.S. patent applications.

In monopolar electrosurgical cutting a current is allowed to pass from an active cutting electrode through a patient's tissue and into a grounding pad or cable. The current cuts tissue at the active cutting electrode, the cutting rate being dependant on current density through the tissue in that area. At low current density heat is generated but no cut is achieved. At high current density fast cutting occurs.

In bipolar electrosurgical cutting the current passes from the active cutting electrode through the patient's tissue to a return electrode which is located in, or is in contact with, the patient's tissue a short distance away from the cutting electrode. The cutting and return electrodes are generally carried by a single instrument.

Current density depends on the current (measured in watts) applied and can be controlled utilizing an adjustment present on a conventional generator designed for this purpose. The current density also depends on the series impedance of the overall circuit. Series impedance is equivalent to the sum total of the resistance to the current throughout the circuit. It is affected by the material and the design of the active electrode, by the patient, by the type of tissue to be cut, and by the condition of contact established between the patient and (when a monopolar electrode is utilized) the grounding pad as well as by the location of the grounding pad relative to the cutting site. During surgery, the generator setting is usually adjusted to compensate for this variability and to reflect the surgeon's preference. Generators used in this type of surgery have a wide range of power output to accommodate a variety of procedures and devices.

The objective in electrosurgical cutting is to heat the tissues cells so rapidly that they explode into steam leaving a cavity in the cell matrix. The heat is meant to be dissipated in the steam and to not conduct through the tissue to thereby dry out adjacent cells. When the electrode is moved and fresh tissue is contacted new cells are exploded and the incision is made. Such electrosurgical cutting involves the sparking of the current to the tissue. The current utilized is in the radio frequency range and operates by the radio frequency current jumping across an air gap to the tissue. This is known as sparking.

An explanation of electrosurgical cutting theory can be found in the FORCE 1 Instruction Manual published by Valleylab of Boulder, Colo. on Mar. 1, 1986. The entire text of the FORCE 1 Instruction Manual is incorporated herein by reference.

In accordance with the embodiment of FIG. 1, a radiopaque marker pattern 22 is provided and is carried by the cutting element support 12. The pattern 22 is such that by fluoroscopic viewing of the pattern 22 (and usually the cutting element 18, as well), a user can determine the angular orientation of the cutting element 18 about its longitudinal axis 26. In the particular embodiment illustrated, the pattern 22 is in the nature of a radiopaque wire 24 which fits in a passage in the cutting element support 12. If one looks downwardly upon the cutting element 18, and aligns the cutting element 18 with the wire 24 so that only a single line is apparent to the surgeon, then the cutting element 18 is aligned to out directly upwardly (the possibility of a 180.degree. misalignment is avoidable since the cutter assembly 10 can be inserted with sufficient care so that it is less than 90.degree. out of alignment) from the longitudinally extending cutting element support 12. Also, the assembly 10 can have markers on its proximal(out-of-body) end to allow positioning within 45.degree. of the desired target orientation. If the cutter assembly 10 is otherwise aligned, for example if it is rotated some number of degrees about the illustrated axis 26, then the surgeon will see two lines in the fluoroscopic picture, one corresponding to the cutting element 18 and the other to the wire 24 (one or more of the lines forming the radiopaque pattern 22 can be made distinguishable from the line representative of the cutter element 18, for example, the pattern lines can be dashed lines, have transverse dashes across them, or the like). The surgeon can then rotate the cutter assembly 10 about the axis 26 until the two visible lines coincide to properly position the cutting element 18 directly above the wire 24.

Generally the radiopaque marker pattern 22 is made up of lines which are relatively thin. In particular, such lines, whether they are made up of wires or are in the nature of radiopaque inks, are no greater in extension (diameter in the case of wires) than is the cutting element 18 itself. If the lines which make up the marker pattern 22 are significantly wider than the cutting element 18 there is an alignment error results since the cutting element 18 can be misaligned at any location opposite the width of the potentially wider lines of the marker pattern 22. Thus, it is preferred that the Width of the lines of the marker pattern 22 be no greater than the width of the cutting element 18.

FIGS. 2 and 3 show an embodiment of the invention wherein the marker pattern 22 comprises two radiopaque markers 28 and 30, each parallel to and extending along the support 12 and each being on the same diameter as seen in FIG. 3. When the surgeon is viewing the cutter assembly 10, of FIGS. 2 and 3 from above, the radiopaque markers 28 and 30 can be aligned to appear to be only a single line, thus assuring proper orientation of, for example, a cutting loop 32, which extends from the distal end portion 14 of the cutting element support 12.

FIG. 4 illustrates an embodiment of a cutter assembly 10'' very much like that of FIG. 3, but wherein the radiopaque marker pattern 22 is in the nature of two wires 34 and 36, both within appropriate passages in the cutting element support 12. A cutting element is not shown but, if present, would extend from the distal end portion of the cutting element support 12. This embodiment is also useful if the element being aligned is not a cutting element and is not itself radiopaque.

FIGS. 5 and 6A and 6B illustrate an embodiment of the present invention wherein the cutter assembly 10''' serves for orientating the cutting element 18 at a desired angle relative to the axis 26. In the embodiment illustrated in FIGS. 5 and 6, there are a plurality of radiopaque indicator lines 38 carried by (in the embodiment illustrated within) the cutting element support 12 and each of the radiopaque indicator lines 38 is laterally removed from a line 39 defined by the intersection of a plane defined by the axis 26 and by the cutting element 18, which is otherwise in the nature shown in FIG. 1. Each of the radiopaque indicator lines 38 is a different distance from this intersection line in order to allow selective angular orientation of the cutting element 18 while it is within a body vessel, cavity, or conduit. For example, the cutting element support 12 can be rotated until the cutting element 18 appears to be over any one of the opaque indicator lines 38, which can be in the nature of radiopaque lines or can be imbedded wires, whereby a cut may be made at a desired orientation about the axis 26. FIGS. 6A and 6B illustrate the alignment procedure.

Also in accordance with the present invention, and adverting particularly to FIG. 1, it is possible to provide additional radiopaque markers 40 and 42, one of which is each end of the cutting element 18. In this way, the surgeon can observe not only the radial direction in which the cutting element 18 is going to proceed on inflating of the balloon 20, but also just where along a body conduit the cutting element 18 is going to cut into the particular body conduit.

In accordance with the method of the invention, the alignable cutter assembly 10, 10', 10'', or 10''', is inserted in a body vessel, cavity, or conduit to the desired depth. Fluoroscopic images are obtained of the cutter assembly 10, 10', 10'', or 10''', within the body. The cutting element 18 is then aligned in a desired angular orientation relative to the axis 26 using the radiopaque marker pattern 22. The precise depth within the body can also be adjusted by observing the radiopaque markers 40 and 42, when present. Thereafter, incising is carried out in the desired direction. If desired, the element can be reoriented in a different angular orientation and an additional incision can be made.

The present invention provides a cutter assembly 10 which allows a cutting element 18 to be aligned properly within a body vessel, cavity, or conduit so as to provide an incision in a desired direction.

While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention and the limits of the appended claims.