ELECTROSURGICAL PROBE WITH ANNULAR ELECTRODES

Abstract: An electrosurgical probe (10) including a shaft (12) having a generally cylindrical shape having a circumference, a proximal end (14) and a distal end (16), a plurality of electrically isolated, annular electrodes (18) disposed on the distal end (16) of the shaft (12), each electrode (18) at least partially encircling the circumference of the shaft (12), the electrodes (18) being electrically connectable to a high frequency voltage source (20).

Description: ELECTROSURGICAL PROBE WITH ANNULAR ELECTRODES FIELD OF THE INVENTION The present invention relates generally to an electrosurgical probe and particularly to such a probe with annular very high frequency electrodes BACKGROUND OF THE INVENTION The field of electrosurgery includes a number of loosely related surgical techniques which have in common the application of electrical energy to modify the structure or integrity of patient tissue Electrosurgical procedures usually operate through the application of very high frequency currents to cut or ablate tissue structures, where the operation can be monopolar or bipolar Monopolar techniques rely on external grounding of the patient, where the surgical device defines only a single electrode pole Bipolar devices comprise both electrodes for the application of current between their surfaces Electrosurgical procedures and techniques are particularly advantageous since they generally reduce patient bleeding and trauma associated with cutting operations Additionally, electrosurgical ablation procedures, where tissue surfaces and volume may be reshaped, cannot be duplicated through other treatment modalities The use of electrosurgical procedures in electrically conductive environments, however, can be problematic For example, many procedures require flushing of the region to be treated with isotonic saline (also referred to as normal saline), both to maintain an isotonic environment and to keep the field of viewing clear The presence of saline, which is a highly conductive electrolyte, can cause shorting of the electrosurgical electrode in both monopolar and bipolar modes Such shorting causes unnecessary heating in the treatment environment and can further cause non-specific tissue destruction Prostate diseases, such as prostate cancer and benign prostatic hypertrophy (BPH), can cause enlargement of the prostate which in turn causes a narrowing of the urethra adjacent the prostate caused by swelling of the surrounding tissue Such narrowing can cause difficulty in urination, resulting in discomfort and exposing the patient to further complications A variety of methods have been proposed for treating enlarged prostates Generally, the methods rely on either reducing the prostatic mass to lessen pressure on the urethra or resecting prostatic tissue adjacent the urethra in order to increase the luminal area for passing urine. The first group of methods include various protocols for directing energy, including microwave radiation, radio frequency energy, and laser energy, to induce an increase in tissue temperature within a defined volume of the prostate Such an increase in tissue temperature, often referred to as "thermotherapy", will be maintained at a temperature and for a time sufficient to cause necrosis of the treated prostate tissue, with the necrosed tissue being subsequently sloughed off or reabsorbed into the surrounding tissue mass Such sloughing off or reabsorption of the necrosed tissue, in turn, will cause size reduction of the prostate, relieving the symptoms of BPH The latter group of methods includes the use of endoscopes introduced through the urethra which allow for controlled tissue resection Of particular interest to the present invention, transurethral prostatic tissue resection techniques are known to employ monopolar "loop" electrodes introduced through conventional resectoscopes for excising tissue along the urethral lumen The treating physician can view the procedure, either directly or over a video screen, and can control the depth of cutting by manually manipulating the position of the electrode while RF energy is applied using conventional electrosurgical power supplies While prostatic tissue resection using such loop electrodes is generally successful, it suffers from a number of deficiencies First, the control of depth of cutting is difficult, placing the patient at risk of serious injury Second, non-conductive (non-physiologic) fluids must be used to flush the region being treated in order to avoid energy dissipation through the fluid. The use of such non-physiologic irrigants, can cause trauma to the tissue and possibly disrupt the electrolyte balance in the bloodstream, resulting in hyponatremia Third, conventional prostatic tissue resection results in the formation of tissue "chips" which must be flushed from the working site and may collect upstream in the bladder Chip removal requires frequent withdrawal of the resectoscope in order to provide sufficient access for effective cleaning Fourth, monopolar tissue resection can cause electrical stimulation of nearby tissue, placing the patient at risk of muscle spasms Fifth, monopolar tissue resection can cause unintended and unwanted heating of tissue, including nerves, in regions near the intended treatment site Such unwanted heating can result from aberrant current pathways from a treatment electrode to a dispersive electrode disposed on the patient's skin In the worst case, unwanted heating can result in unintended tissue necrosis, leading possibly to irreversible nerve damage A particularly relevant example of a radio frequency (RF) electrode is described in US Patent 5,681,282 to Eggers et al., the disclosure of which is incorporated herein by reference. In Eggers et al., an electrode array, including a plurality of electrically isolated electrode terminals, is engaged against a wall of a body lumen, such as against the mucosal surface of the prostate within the urethra The electrode array is located at the distal end of a probe, the probe being introduced by conventional transurethral or suprapubic access roots In the case of transurethral introduction, the probe is typically passed through a conventional viewing scope having a working lumen, such as a resectoscope After positioning the electrode array at the target site, high frequency voltage is applied between the array and one or more common electrodes, in either a monopolar or a bipolar manner A laterally outward force is applied on the electrode array to ablate peripheral tissue in the lumen, typically in combination with axial and/or transverse translation of the surface to effect the desired depth of ablation SUMMARY OF THE INVENTION The present invention seeks to provide an improved electrosurgical probe which comprises a plurality of annular very high frequency electrodes Unlike the loop electrodes of the prior art, the electrosurgical probe of the present invention does not perform resection and does not normally require anesthesia The probe of the present invention is not a resection probe but is rather inserted into the body like a catheter The electrosurgical probe includes a plurality of annular electrodes which can be used in a monopolar or bipolar mode Pairs of electrodes can be energized in many different kinds of combinations in order to cause necrosis of the prostate in an optimal manner in accordance with a particular treatment plan. It is noted that although the probe of the present invention is described for use with prostate treatment, nevertheless the probe of the present invention is not limited to the prostate but may be used for any kind of suitable body organ or cavity There is thus provided in accordance with a preferred embodiment of the present invention an electrosurgical probe including a shaft having a generally cylindrical shape having a circumference, a proximal end and a distal end, a plurality of electrically isolated, annular electrodes disposed on the distal end of the shaft, each electrode at least partially encircling the circumference of the shaft, the electrodes being electrically connectable to a high frequency voltage source In accordance with a preferred embodiment of the present invention a connector is disposed near the proximal end of the shaft for electrically connecting the electrodes to the high frequency voltage source Preferably the electrodes have generally the same potential Further in accordance with a preferred embodiment of the present invention the shaft is flexible along at least a portion of its length Still further in accordance with a preferred embodiment of the present invention at least a distal portion of the shaft is rigid. Additionally in accordance with a preferred embodiment of the present invention the shaft is at least partially hollow. In accordance with a preferred embodiment of the present invention the shaft is formed with a plurality of holes for passage therethrough of fluids. Further in accordance with a preferred embodiment of the present invention the shaft includes a printed circuit substrate suitable for printing thereupon printed circuit lines, and the plurality of annular electrodes include a plurality of printed circuit lines printed on the substrate, the substrate being rolled into a generally, at least partially cylindrical shape. Additionally in accordance with a preferred embodiment of the present invention a controller is in electrical communication with the probe for controlling operation of the probe. Further in accordance with a preferred embodiment of the present invention a transrectal probe or transurethral endoscope is in electrical communication with the controller. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: Fig. 1 is a simplified pictorial illustration of an electrosurgical probe constructed and operative in accordance with a preferred embodiment of the present invention; Fig. 2 is a simplified pictorial illustration of the electrosurgical probe of Fig. 1 inserted in a urethra; Fig. 3 is a simplified, side view illustration of the electrosurgical probe of Fig. 1 inserted in the urethra, used in conjunction with a transrectal probe or transurethral endoscope; Fig. 4 is a simplified pictorial illustration of using the electrosurgical probe of Fig. 1 to cause necrosis of prostate tissue in accordance with a preferred embodiment of the present invention; and Fig. 5 is a simplified pictorial illustration of an electrosurgical probe constructed and operative in accordance with another preferred embodiment of the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Reference is now made to Figs. 1-3 which illustrate an electrosurgical probe 10 constructed and operative in accordance with a preferred embodiment of the present invention. Electrosurgical probe 10 preferably includes a shaft 12 having a generally cylindrical shape, with a proximal end 14 (Figs 2 and 3) and a distal end 16 A plurality of electrically isolated, annular electrodes 18 are preferably disposed on the distal end 16 Electrodes 18 most preferably completely encircle the circumference of shaft 12, but depending on the application, one or more electrodes 18 may partially encircle the circumference of shaft 12 Electrodes 18 are preferably electrically connected to a high frequency voltage source 20 Although wires individually connected to each electrode 18 may extend from the proximal end 14, however, most preferably a connector 23 (Fig 2) is disposed near proximal end 14 for electrically connecting electrodes 18 to high frequency voltage source 20 Preferably electrodes 18 have generally the same potential For ease of entry into the urethra, shaft 12 is preferably flexible along at least a portion of its length However, for some applications it is preferable that at least a portion of shaft 12 be rigid, such as towards distal end 16 Shaft 12 is preferably at least partially hollow and is preferably formed with a plurality of holes 22 for passage therethrough of fluids, such as isotonic saline, for example A controller 24 is preferably in electrical communication with probe 10 and controls operation thereof Electrodes 18 may be bipolar, in which case an auxiliary electrode 26 (Fig 3) is placed at some other location in or on the patient, such as on the back of the patient, and is energized together with one or more electrodes 18 on the probe 10 Alternatively, electrodes 18 may be monopolar, in which case different pairs of electrodes 18 on probe 10 are energized to cause necrosis of the prostate tissue In any case, controller 24 controls which pairs of electrodes 18 are energized in accordance with the type of treatment plan selected for the particular patient An example of a treatment plan as controlled by controller 24 is now described with reference to Fig 4 As seen in Fig 4, in the case of bipolar electrodes, controller 24 can cause energization of two adjacent electrodes A and B This causes a current to arc between the electrodes and cause necrosis in a somewhat toroidal band 30 in the region near these electrodes Subsequently, two other electrodes C and D, separated from each other by electrodes A and B, can be energized Since the distance between electrodes C and D is greater than the distance between electrodes A and B, the current flowing between electrodes C and D causes necrosis of tissue in a larger toroidal region 32 than that caused by energization of electrodes A and B The process can then be continued for further spaced electrodes 18 to cause necrosis of a relatively large area of a prostate 36 As seen in Fig 3, probe 10 may be used in conjunction with a transrectal probe 37 or a transurethral endoscope 38, both of which are in electrical communication with controller 24 Additionally, imaging apparatus 34, such as fluoroscope or ultrasound apparatus, may be used to monitor the operation of probe 10 Cooling apparatus 39 may be provided for supplying cooling fluid through the urethra Reference is now made to Fig 5 which illustrates an electrosurgical probe 40 constructed and operative in accordance with another preferred embodiment of the present invention Electrosurgical probe 40 preferably includes a shaft 42 constructed of a printed circuit substrate 43 suitable for printing thereupon printed circuit lines Substrate 43 is preferably rolled into a generally, at least partially cylindrical shape, having a proximal end 44 and a distal end 46 A plurality of electrically isolated, annular electrodes 48 are disposed on shaft 42 Most preferably electrodes 48 are formed on substrate 43 as a plurality of printed circuit lines printed thereupon As described similarly above for probe 10, electrodes 48 most preferably completely encircle the circumference of shaft 42, but depending on the application, one or more electrodes 48 may partially encircle the circumference of shaft 42 Electrodes 48 are preferably electrically connected to high frequency voltage source 20 and controller 24 (Figs. 1-3), as described hereinabove for probe 10 Substrate 43 is preferably formed with a plurality of holes 52 for passage therethrough of fluids The operation of probe 40 is preferably substantially the same as probe 10 It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove Rather the scope of the present invention includes both combinations and subcombinations of the features described hereinabove as well as modifications and variations thereof which would occur to a person of skill in the art upon reading the foregoing description and which are not in the prior art

Claims: C L A I M S What is claimed is: 1. An electrosurgical probe (10) comprising: a shaft (12) having a generally cylindrical shape having a circumference, a proximal end (14) and a distal end (16); a plurality of electrically isolated, annular electrodes (18) disposed on the distal end (16) of the shaft (12), each electrode (18) at least partially encircling the circumference of the shaft (12), said electrodes (18) being electrically connectable to a high frequency voltage source (20). 2. The probe (10) according to claim 1, further comprising a high frequency voltage source (20) to which said electrodes (18) are electrically connected. 3. The probe (10) according to claim 2, further comprising a connector (23) disposed near the proximal end (14) of the shaft (12) for electrically connecting the electrodes (18) to said high frequency voltage source (20). 4. The probe (10) according to any of the preceding claims, wherein said electrodes (18) have generally the same potential. 5. The probe (10) according to any of the preceding claims, wherein the shaft (12) is flexible along at least a portion of its length. 6. The probe (10) according to any of the preceding claims, wherein at least a distal portion of the shaft (12) is rigid. 7. The probe (10) according to any of the preceding claims, wherein said shaft (12) is at least partially hollow. 8. The probe (10) according to any of the preceding claims, wherein said shaft (12) is formed with a plurality of holes (22) for passage therethrough of fluids. 9. The probe (40) according to any of the preceding claims, wherein said shaft (42) comprises a printed circuit substrate (43) suitable for printing thereupon printed circuit lines, and said plurality of annular electrodes (48) comprise a plurality of printed circuit lines printed on said substrate (43), said substrate (43) being rolled into a generally, at least partially cylindrical shape. 10. The probe (10) according to any of the preceding claims, further comprising a controller (24) in electrical communication with said probe (10) for controlling operation of said probe (10). 11. The probe (10) according to claim 10, further comprising a transrectal probe (37) in electrical communication with said controller (24). 12. The probe (10) according to claim 10, further comprising a transurethral endoscope (38) in electrical communication with said controller (24).

Inventors: EIN-GAL MOSHE, EIN-GAL, MOSHE
Applicants: EIN GAL MOSHE, EIN-GAL, MOSHE
Application year: 1999
Main classification: A61B18
IPC codes: A61B18