Patent Application
20130085495
The invention relates generally to the structure and use of radiofrequency electrosurgical apparatus for the treatment of tissue. More particularly, the invention relates to an electrosurgical system having pairs of electrode arrays, which are deployed to treat large volumes of tissue, particularly for the treatment of tumors in the liver and other tissues and organs.
The delivery of radiofrequency energy to treatment regions within tissue is known for a variety of purposes. Of particular interest to the invention, radiofrequency energy may be delivered to diseased regions in target tissue for the purpose of causing tissue necrosis. For example, the liver is a common depository for metastases of many primary cancers, such as cancers of the stomach, bowel, pancreas, kidney, and lung. Electrosurgical probes for deploying multiple electrodes have been designed for the treatment and necrosis of tumors in the liver and other solid tissues. See, for example, the LeVeen™ Needle Electrode available from Boston Scientific Corporation, which is constructed generally in accordance with published PCT application WO 98/52480.
The probes described in WO 98/52480 comprise a number of independent wire electrodes, which are extended into tissue from the distal end of a cannula. The wire electrodes may then be energized in a monopolar or bipolar fashion to heat and necrose tissue within a defined generally spherical volumetric region of target tissue. In order to assure that the target tissue is adequately treated and to limit damage to adjacent healthy tissues, it is desirable that the array formed by the wire electrodes within the tissue be precisely and uniformly defined.
Despite the significant success that has accompanied use of the LeVeen™ Needle Electrode in treating solid tissue tumors, the ability to treat particular types of tumors has been somewhat limited. For example, the ability to produce very large tissue lesions, for example lesions having volumes greater than 30-35 cm3, has been problematic. In addition, such larger tumors tend to be less spheroidal in shape than smaller tumors. Since the LeVeen™ Needle Electrode produces generally spheroidal lesions, the ability to treat larger, non-spheroidal tumors can be limited. Additionally, the ability to treat highly vascularized tissues and/or tissue near a large blood vessel has also been limited. In the latter cases, heat being introduced by the electrode can be rapidly carried away by circulating blood, making uniform heating and control of temperature in the vascularized tissues difficult. Uniform heating and temperature control of the tissue being treated is, of course, one prerequisite to obtaining homogenous lesions in and around the tumors.
The ability to provide uniform heating and the creation of homogenous tissue lesions is particularly difficult with bipolar devices. The two bipolar electrodes may be placed in regions with quite different perfusion characteristics, and the heating around each pole can be quite different. That is, one pole may be located adjacent to a large blood vessel, while the other pole may be located adjacent to tissue, which is less perfused. Thus, the pole located in the less perfused tissue will heat the tissue immediately surrounding the electrode much more rapidly than the tissue surrounding the opposite polar electrode is heated. In such circumstances, the tissue surrounding one pole may be preferentially heated and necrosed, while the tissue surrounding the other pole will neither be heated nor necrosed sufficiently.
To address these issues, a bipolar dual electrode array probe, as described in U.S. patent application Ser. No. 09/663,048, entitled “Methods and Systems for Focused Bipolar Tissue Ablation,” which is expressly incorporated herein by reference, has been developed. As shown in
For this reason, it would be desirable to provide improved bipolar electrosurgical methods and systems for more uniformly ablating tumors in the liver and other body organs.
In accordance with preferred embodiments of the present inventions, a tissue ablation probe is provided. The probe comprises proximal and distal electrode arrays, each of which has a retracted configuration and a deployed configuration. The probe further comprises a shaft for carrying the electrode arrays. In one embodiment, the electrode arrays are electrically isolated from each other and have respective concave faces that oppose each other when in the deployed configuration, thereby enhancing the bipolar nature of the probe. In forming a concave face, an electrode array may comprise a plurality of individual electrodes that initially move axially and then evert as they are deployed. In another embodiment, the shaft comprises a proximal conductive tube from which the proximal electrode array is deployed, and a distal conductive tube from which the distal electrode array is deployed. The conductive tubes may, e.g., be coaxial relative to each other or may be in a side-by-side relationship.
In accordance with one aspect of the present inventions, the electrode arrays have distal termini, and the shaft has an electrically insulative portion that separates the electrode arrays. In one embodiment, the insulative portion is continuous, but may also have gaps. The shaft portion can be insulated in any one of a variety of ways, but in one embodiment, the insulative shaft portion comprises an electrically conductive wall on which electrically insulative material is disposed. The electrode arrays are separated from each other by a first length when deployed, and the insulative shaft portion spans a second length greater than seventy-five percent of the first length. By way of non-limiting example, the insulative shaft portion may allow most of the electrical current to flow between the electrode arrays, rather than along the normally conductive shaft, thereby enhancing the shape of the resulting tissue ablation. The second length may be further increased relative to the first length (e.g., equal to or greater than) to allow even more electrical current to flow between the electrode arrays.
In accordance with another separate aspect of the present inventions, the shaft has an intervening portion between the electrode arrays. The intervening portion has an electrically conductive proximal region, an electrically conductive distal region, and a non-conductive gap therebetween. The probe further comprises an electrically insulative material covering at least portions of the proximal and distal shaft regions. Optionally, the insulative material may also cover the non-conductive gap. By way of non-limiting example, the application of the insulative material on the conductive shaft provides a convenient means of modifying the amount of current that flows between the electrode arrays. In one embodiment, the insulative material is closer to one of the electrode arrays than the other. In this manner, the flow of electrical current adjacent one array can be modified relative to the other array.
In accordance with still another separate aspect of the present inventions, the probe comprises proximal and distal electrically conductive tubes that are electrically isolated from each other. The proximal electrode array is proximally deployable from and electrically coupled to the proximal tube, and the distal electrode array distally deployable from and electrically coupled to the distal tube. The probe further comprises an electrically insulative material covering at least portions of the proximal and distal tubes. In one embodiment, the insulative material continuously extends from the proximal tube to the distal tube, and, depending on the desired proportion of electrical current conveyed between the electrode arrays, may cover the entirety of the proximal and distal tubes.
In accordance with other preferred embodiments of the present inventions, another tissue ablation probe is provided. The probe comprises a proximal electrode element that includes a proximal electrode stem and a deployable proximal electrode array, which has distal termini and is electrically coupled to a proximal end of the proximal electrode stem when deployed. The probe further comprises a distal electrode element including a distal electrode stem and a deployable distal electrode array, which has distal termini and is electrically coupled to a distal end of the distal electrode stem when deployed. The electrode arrays may have the same features as the electrode array previously described above. The probe is configured, such that a majority of electrical energy conveyed between the proximal and distal electrode elements is conveyed between distal termini of the electrode arrays. In some embodiments, substantially all of the electrical energy conveyed between the proximal and distal electrode elements is conveyed between distal termini of the electrode arrays. In one embodiment, the proximal electrode stem comprises a proximal conductive tube from which the proximal electrode array is deployed, and the distal electrode stem comprises a distal conductive tube from which the distal electrode array is deployed.
In accordance with a preferred method of the present invention, a target tissue region (e.g., a tumor within an organ such as the liver, lung, kidney, pancreas, stomach, uterus, or spleen) is treated. The method comprises deploying a first electrode array on one side of the tissue region, and deploying a second electrode array on another side of the tissue region, such that the electrode arrays define a periphery therebetween. The method further comprises transmitting electrical energy (e.g., at a frequency in the range from 300 kHz to 1.2 MHz and at a power in the range of 50W to 300W) from the first electrode array to the second electrode array, so that the tissue region along the periphery is initially ablated. In one method, the core of the tissue region within the periphery is subsequently ablated. By way of non-limiting example, this method will typically produce a more uniform ablation.
In accordance with another preferred embodiment of the present inventions, a tissue ablation probe is provided. The probe comprises an array of needle electrodes having a retracted configuration and a deployed configuration, and a shaft carrying the electrode array. The probe further comprises an electrically insulative material partially disposed on at least one needle electrode of each array, whereby a tip of the needle electrode(s) is left exposed. For example, the insulative material can be disposed on the needle electrode(s) at a point on the shaft from which the needle electrodes deploy to somewhere along the length of the needle electrode(s). In one embodiment, the insulative material may be partially disposed on all the needle electrodes of each array, whereby tips of the needle electrodes are left exposed. By way of non-limiting example, the electrical insulation of portions of the needle electrode(s) allows the electrical current to be more focused at the tips of the electrode array, thereby providing for a greater tissue ablation. In one embodiment, the probe comprises proximal and distal electrode arrays on which the electrically insulative material is applied. In this case, the shaft and electrode arrays can optionally have the same features as the electrode arrays previously described above to further enhance bipolar ablation between the arrays.
Other and further aspects and features of the invention will be evident from reading the following detailed description of the preferred embodiments, which are intended to illustrate, not limit, the invention.
The drawings illustrate the design and utility of preferred embodiment(s) of the invention, in which similar elements are referred to by common reference numerals. In order to better appreciate the advantages and objects of the invention, reference should be made to the accompanying drawings that illustrate the preferred embodiment(s). The drawings, however, depict the embodiment(s) of the invention, and should not be taken as limiting its scope. With this caveat, the embodiment(s) of the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
Generally, the invention is directed to the use of RF electrode arrays, particularly bipolar electrode arrays, for the ablation of treatment regions within solid tissue of a patient. The treatment regions may be located anywhere in the body where hyperthermic exposure may be beneficial. Most commonly, the treatment region will comprise a solid tumor within an organ of the body, such as the liver, lung, kidney, pancreas, breast, prostate (not accessed via the urethra), uterus, and the like. The volume to be treated will depend on the size of the tumor or other lesion, but embodiments of the invention are particularly suitable for treating relatively large tissue regions. The peripheral dimensions of a particular treatment region may be regular, e.g., spherical or ellipsoidal, but will more usually be somewhat irregular. The lesion created to enclose the target tissue region utilizing embodiments of this invention will usually be cylindrical or a truncated conical volume, as described in more detail below. The treatment region may be identified using conventional imaging techniques capable of elucidating a target tissue, e.g., tumor tissue, such as ultrasonic scanning, magnetic resonance imaging (MRI), computer-assisted tomography (CAT), fluoroscopy, nuclear scanning (using radiolabeled tumor-specific probes), and the like. Preferred is the use of high-resolution ultrasound, which can be employed to monitor the size and location of the tumor or other target tissue, being treated, either intraoperatively or externally.
Apparatus according to embodiments of the invention will usually comprise at least one probe having a distal end adapted to be positioned beneath a tissue surface at or near the treatment region or regions. A first array of electrodes comprising a plurality of tissue-penetrating electrodes, typically in the form of sharpened, small cross-section metal elements are reciprocatably attached to the probe so that they penetrate into tissue as they are advanced from a first specific site (referred to hereinafter as the first target site) at or adjacent to a peripheral boundary of the treatment region, as described in more detail hereinafter. The primary requirement of such electrode elements is that they can be deployed in an array, preferably a three-dimensional array, emanating from the first treatment site within the treatment region of the tissue. Usually, the first electrode array will be deployed from a first target site on a “distal” side of the treatment region, i.e., the side that is most remote from the organ or tissue entry point. In the exemplary embodiments, the electrode elements are first introduced to the treatment region in a radially collapsed or other constrained configuration, and thereafter advanced into the tissue from a delivery cannula or other element in a divergent pattern to achieve the desired three-dimensional array. The electrode elements will diverge radially outwardly from the delivery cannula (located at the first target site) in a uniform pattern, i.e., with the spacing between adjacent electrodes diverging in a substantially uniform and/or symmetric pattern. Preferably, adjacent electrodes will be spaced-apart from each other in similar or identical, repeated patterns and will usually be symmetrically positioned about an axis of the delivery element. The electrode elements may extend or project along generally straight lines from the probe, but will more usually be shaped to curve radially outwardly and to evert proximally so that they face partially or fully in the proximal direction when fully deployed. It will be appreciated that a wide variety of particular patterns can be provided to uniformly cover the region to be treated.
Apparatus according to embodiments of the invention will also comprise at least a second array of electrodes comprising a plurality of tissue-penetrating electrodes typically in the form of sharpened, small cross-section metal wires or elements. The second electrode array will usually be attached to the same probe as is the first electrode array. In some instances, however, the use of such embodiments may utilize first and second electrode arrays, which are deployed from separate probes and operated in a bipolar manner, as, described in more detail below. The electrode wires or elements of the second array will be deployed from a second target site within the treatment region, usually on a “proximal” side thereof, i.e., the side which is closest to the organ or tissue entry point. The electrodes of the second array will be introduced similarly to those of the first array, i.e., in a collapsed configuration, and subsequently deployed radially outwardly. In the exemplary embodiments, both the first and the second electrode arrays include everting electrode elements, which form arrays having generally concave and convex surfaces. By facing the concave surfaces and electrode tips of the two electrode arrays toward each other so that they are generally aligned along a common axis, usually defined by a shaft of the probe, radiofrequency and other high frequency currents may be applied to tissue in a manner which creates a uniform lesion, i.e., a lesion which is continuous and without significant portions of viable tissue, even when the region has portions which have different perfusion and different cooling characteristics.
Referring now to
The first electrode array 12 has a concave surface 22 and a convex surface 24, and the second electrode array 14 also has a concave surface 26 and a convex surface 28. In the illustrated embodiment, the concave surfaces at 22 and 26 of the electrode arrays 12 and 14 face each other along the axis line 18, so that a distance l1 is defined between distal termini 13 and 15 (i.e., the tips of the electrode wires) of the electrode arrays 12 and 14. The axial electrode stems 16 and 20 also face each other and extend toward each other, leaving a distance l2 between the inner termini 17 and 21 (i.e., the tips) of the electrode stems 16 and 20.
As shown in
As shown in
In exemplary methods of the invention, the electrode arrays 12 and 14 will be disposed within tissue on opposite sides of a treatment region. The arrays will be disposed generally as shown in
The RF power supply 32 may be a conventional general purpose electrosurgical power supply operating at a frequency in the range from 300 kHz to 1.2 MHz, with a conventional sinusoidal or non-sinusoidal wave form. Such power supplies are available from many commercial suppliers, such as Valleylab, Aspen, and Bovie. Most general purpose electrosurgical power supplies, however, are constant current, variable voltage devices and operate at higher voltages and powers than would normally be necessary or suitable. Thus, such power supplies will usually be operated initially at the lower ends of their voltage and power capabilities, with voltage then being increased as necessary to maintain current flow. More suitable power supplies will be capable of supplying an ablation current at a relatively low fixed voltage, typically below 200 V (peak-to-peak). Such low voltage operation permits use of a power supply that will significantly and passively reduce output in response to impedance changes in the target tissue. The output will usually be from 50 W to 300 W, usually having a sinusoidal wave form, but other wave forms would also be acceptable. Power supplies capable of operating within these ranges are available from commercial vendors, such as Boston Scientific Therapeutics Corporation. Preferred power supplies are model RF-2000 and RF-3000, available from Boston Scientific Corporation.
The geometry and volume of the treatment region within the patient tissue can determined by controlling various dimensions of the apparatus. For example, the arrays 12 and 14 will usually have outer circular diameters D in the range from 1 cm to 6 cm, usually from 2 cm to 4 cm. The diameters of each array will usually be the same, although they could differ in certain circumstances. When the diameters are the same, the geometry of the lesion created will be generally cylindrical. When the diameters are different, the geometry could generally be a truncated cone. The distance l1 between the inner termini 13 and 15 of the electrode arrays 12 and 14 will usually be in the range from 2 cm to 10 cm, more usually in the range from 3 cm to 7 cm, and preferably in the range from 4 cm to 6 cm. The axial electrode stems 16 and 20 will typically have a length in the range from 0.0 cm (i.e., non-existent) to 2 cm.
Based on the distance l1, the desired shape of the resulting ablation lesion, and the desired ablation time, the distance l2 between the inner termini 17 and 21 of the axial stems 16 and 20 is selected to control the proportion of current flowing between the distal termini 13 and 15 of the electrode arrays 12 and 14 relative to the current flowing between the inner termini 17 and 21 of the electrode stems 16 and 20.
It has been discovered that, in general, the greater the proportion of current flowing between the distal termini 13 and 15 of the electrode arrays 12 and 14, as opposed to current flowing between the inner termini 17 and 21 of the electrode stems 16 and 20, the more uniform the resulting ablation lesion will be along the periphery of the tissue treatment region (e.g., so that the ablation lesion is more cylindrical, rather than hour-glass shaped), but the greater the time needed to ablate the tissue core along the axis 18. In contrast, the greater the proportion of current flowing between inner termini 17 and 21 of the electrode stems 16 and 20, the less uniform the resulting ablation lesion will be along the periphery of the tissue treatment region, but the lesser the time needed to ablate the tissue core along the axis 18.
With this phenomenon in mind, the distance l2 is preferably selected relative to the distance l1, such that a majority of the current, and preferably substantially all of the electrical current, will essentially flow between distal termini 13 and 15 of the electrode arrays 12 and 14, while a small or minimal amount of current flows between the inner termini 17 and 21 of the electrode stems 16 and 20. It has been discovered that the preferred distance l2 should be greater than fifty percent of the distance l1 in order to ensure that the majority of the electrical current flows between the distal termini 13 and 15 of the respective electrode arrays 12 and 14. Optimally, the distance l2 should be greater than seventy-five percent of the distance l1 in order to ensure that substantially all of the electrical current flows between the distal termini 13 and 15 of the respective electrode arrays 12 and 14. In some cases, the distance l2 may be greater than the distance l1, as illustrated in
Thus, it will be appreciated that by increasing the proportion of current flowing between the distal termini 13 and 15 of the electrode arrays 12 and 14 and increasing the ablation time, the treatment region will be heated and necrosed from the outer regions inward towards the center region, thus enhancing the ability to completely and uniformly necrose the entire tissue volume of the treatment region defined by the outward perimeters of the arrays 12 and 14.
It has been discovered that the axial symmetry of a resulting ablation lesion can be modified by selecting the distances l3 and l4 relative to each other. In particular, as the distance l4 decreases relative to the distance l3 (assuming the arrangement in
Referring to
Referring to
Referring to
The previously described electrode elements 8 and 10 will typically be integrated within a probe for deployment within a patient's body. The probe will usually comprise an elongate shaft, typically a rigid or semi-rigid, metal or plastic cannula. In some cases, the cannula will have a sharpened tip, e.g., be in the form of a needle, to facilitate introduction to the tissue treatment region. In such cases, it is desirable that the cannula or needle be sufficiently rigid, i.e., have sufficient column strength, so that it can be accurately advanced through tissue. In other cases, the cannula may be introduced using an internal stylet, which is subsequently exchanged for one or more of the electrode arrays. In the latter case, the cannula can be relatively flexible since the initial column strength will be provided by the stylet. The cannula serves to constrain the individual electrode elements of the electrode arrays in a radially collapsed configuration to facilitate their introduction to the tissue treatment region. The first electrode array can then be deployed to its desired configuration, usually a three-dimensional configuration, by extending distal ends of the electrode elements from the distal end of the cannula into the tissue. In the preferred case of the tubular cannula, this can be accomplished simply by advancing the distal ends of the electrode elements of the first electrode array distally from the tube so that they emerge and deflect (usually as a result of their own spring or shape memory) in a radially outward pattern. The electrode arrays of the second electrode array may then be proximally advanced from the tube so that they emerge and deflect (again, usually as a result of their own spring or shape memory) in a radially outward pattern, which is a mirror image of the pattern formed by the first electrode array. Particular devices employing a single probe or elongate member for deploying such spaced-apart arrays will be described in more detail below.
Referring now to
The handle 68, in turn, includes a stationary portion 70 and a rotatable portion 72. The rotatable portion 72 has a first threaded channel 74, which receives the threaded end 60 of the distal array slider 58. A second threaded channel 76 receives the threaded end 66 of the proximal yoke 64. In this way, rotation of the rotatable part 72 of handle 68 will simultaneously advance the distal slider 58 to deploy the distal electrode array 52 and retract the proximal yoke 64 which will deploy the proximal array 54, as best illustrated in
The proximal conductor 62 extends distally through an insulated outer sheath 80 and past a gap 82 (
While the proximal array 54 is being proximally deployed, the distal array 52 is simultaneously being deployed by advancing distally outwardly from the distal conductive tube 86 at the distal end of the probe 50. When fully deployed, as shown in
It can be appreciated that the proximal conductive tube 84 effectively forms a proximal electrode stem, such as the stem 20 illustrated in
The insulative material 92 may be applied to the probe 50 equidistantly between the electrode arrays 52 and 54 to form the electrode configuration illustrated in
Referring now to
Unlike probe 50, however, the distal array 102 and proximal array 104 are disposed in different, parallel tubular structures. As best shown in
It can be appreciated that the proximal conductive tube 122 effectively forms a proximal electrode stem, such as the stem 20 illustrated in
In addition to the provision of insulation on the shafts of the previously described probes 50 and 100, electrical insulation can be also be provided on the needles of the electrode arrays. For example,
As shown, the needles are substantially insulated from a point of deployment 158 to a peak of an arch 160 formed by each needle. In this manner, the electrical current conveyed between the electrode arrays 150 and 152 will be concentrated at the tips 156, thereby maximizing the radius of the resulting ablation lesion. Nevertheless, in some instances, the maximum may not be preferred and therefore, one of skill in the art will appreciate that the needles may be insulated along any portion between the point of deployment 158 and any designated point along the needle. Although all of the needles are shown to be partially insulated, less than all of the needles may be insulated, depending on the desired shaped of the ablation.
Although particular embodiments of the present invention have been shown and described, it should be understood that the above discussion is not intended to limit the present invention to these embodiments. It will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. Thus, the present invention is intended to cover alternatives, modifications, and equivalents that may fall within the spirit and scope of the present invention as defined by the claims.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10971373 | Oct 2004 | US |
| Child | 13685532 | US |
