SHEATH, CRYOPROBE, AND METHODS FOR USE

Abstract: A cryoprobe (2) is described having a Joule-Thomson nozzle (34) and heat exchanger (30) contained within a first sheath (20) in which the first sheath has an insulating layer (44) disposed proximally with respect to the heat exchanger, wherein the insulating layer affects the shape of the ice formed on the cryoprobe. In an alternate embodiment, a cryoprobe is described having an outer sheath (56) surrounding a first sheath whereby gas leaks from the first sheath are prevented from harming the patient.

Description: DESCRIPTION Sheath, Cryoprobe, And Methods For Use Field of the Invention The present invention relates to cryoprobes, and to cryoprobes for use in cryosurgery. In particular, the invention relates to sheathed cryoprobes capable of shaping ice balls formed thereon and to methods of endometrial ablation and other surgical procedures using such cryoprobes . Background of the Invention Cryosurgical probes are used to treat a variety of diseases. The cryosurgical probes quickly freeze diseased body tissue, causing the tissue to die after which it will be absorbed by the body or expelled by the body. Cryothermal treatment is currently used to treat prostate cancer and benign prostate disease, breast tumors and breast cancer, liver tumors and cancer, glaucoma and other eye diseases. Cryosurgery is also proposed for the treatment of a number of other diseases. The use of cryosurgical probes for cryoablation of the uterus is described in Cahan, .G. and Brockunier, A., Cryosurgery of the Uterine Cavity. Am. Obstet. Gynec. 99:138-153, 1967. Cahan and Brockunier describe a cryosurgical probe patterned after the curve and diameter of a No. 6 Hegar dilator. Liquid nitrogen circulates through this cryosurgical probe in order to cause cryonecrosis of the diseased endometrial tissue in the uterus. Multiple applications of freezing and thawing are applied using the curved probe in order to treat left and right cornu of the uterus as well as the fundus. This method of cryosurgery has a number of drawbacks because the uterus has, for example, an irregular shape resulting from the left and right cornu. Moreover, the uterus has a rough and irregular lining which is not amenable to efficient cryosurgery. Because of the uterus' s irregular shape and rough lining, a clinician will often miss a portion of the diseased tissue and must subject the patient to multiple sessions of cryosurgery. A number of approaches have been developed to more efficiently perform cryo-endometrial ablation. For example, Droegemueller et al., U.S. Pat. No. 3,924,628, disclose a flexible bladder which is inserted into the uterus. Using a metal catheter, liquid nitrogen is pumped into the bladder that distends to contact the varied surface of the uterine inner lining. However, the bladder is difficult to position properly and may miss portions of diseased tissue. Coleman et al, U.S. Pat. No. 5,403,309, disclose a cryosurgical probe having a channel for introduction of a heat-conducting liquid into bodily cavities such as the uterus or bladder. A cryoprobe, preferably a Joule- Thompson probe, then cools the heat-conducting liquid to induce cryonecrosis of the diseased tissue. The above methods, however, all suffer from safety problems that are particularly acute for the highly vascular tissue of the uterus. Joule-Thomson probes use high-pressure gas that, should the probe leak, could easily cause gas embolism in such vascular tissue. Thus, there is a need for a cryoprobe providing greater assurance against possible gas leaks. Cryoprobes may be used, as mentioned above, to treat diseases of the prostate, liver, and breast, and they have gynecological applications as well. The cryosurgical probes form ice balls which freeze diseased tissue. Each application has a preferred shape of ice ball, which, if capable of production, would allow cryonecrosis of the diseased tissue without undue destruction of surrounding healthy tissue. For example, prostate cryoablation optimally destroys the lobes of the prostate, while leaving the surrounding neurovascular bundles, bladder neck sphincter and external sphincter undamaged. The prostate is wider at the base and narrow at the apex. A pear or fig shaped ice ball is preferred for this application. Breast tumors tend to be small and spherical so that spherical ice balls are desired to destroy the tumors without destroying surrounding breast tissue. Liver tumors may be larger and of a variety of shapes, including spherical, olive shaped, hot dog shaped or irregularly shaped, and may require more elongated ice balls larger ice balls, and ice balls of various shapes . U. S. Pat. Application Ser. No. 08/685,233, filed July 28, 1996 in the name of Paul Mikus, the contents of which are incorporated by reference in their entirety as if set forth herein, discloses Joule-Thomson cryoprobes adapted to shape the type of ice ball formed thereon. By varying the length of the heat exchanger coils, the distance between the Joule-Thomson nozzle and the heat exchanger distal end, and the distance between the end of the heat exchange chamber and the Joule-Thomson nozzle, various ice ball shapes are formed. Preferably, a flow-directing sheath is used to further affect the shape of the desired ice ball. Despite the advances set forth by Mikus, there remains a need in the art for a clinician to have greater control over ice ball shape formation. Summary of the Invention In one innovative aspect a cryoprobe in accordance with the present invention may comprise a Giaque-Hampson heat exchanger with finned tube gas supply line coiled around a mandrel. The distal portion of the finned tube gas supply line ends in a Joule-Thomson nozzle. An expansion chamber is located distally with respect to the Joule-Thomson nozzles. After exiting the Joule-Thomson nozzles and expanding in the expansion chamber of the cryoprobe, the gas flows over the coils and exhausts out the proximal end of the probe. Proximal to the heat exchanger is a coaxially- disposed insulating layer on the sheath upon which ice formation is curtailed, thereby affecting the shape of the formed ice ball. The insulating layer may be tapered or of a uniform thickness. In an another embodiment of the invention, an outer sheath is coaxially disposed about the cryoprobe sheath defining a space there between. A heat-conducting fluid may be used to fill the space between the outer sheath and the cryoprobe sheath to enhance ice formation. The outer sheath is fastened to the handle of the probe with an adapter. In one embodiment, a channel extends through the adapter to an output port whereby the output port is in fluid communication with the space between the sheath and the outer sheath. A sensor, which can be a pressure transducer or a chemical sensor, is associated with the output port and detects the presence of gas leaks. Brief Description of the Drawings FIG. 1 is a schematic drawing of a cryoprobe in use during an endometrial ablation procedure. FIG. 2 is a view of an insulating layer with a single coil Giaque-Hampson heat exchanger according to one embodiment of the invention. FIG. 3 is a view the distal end of a cryoprobe illustrating an insulating layer with a dual helix heat exchanger according to one embodiment of the invention. FIG. 4 is a view of a cryoprobe with an outer sheath, adapter, and a pressure sensor port according to one embodiment of the invention. FIG. 5 is a view of an outer sheath and an adapter according to one embodiment of the invention. FIG. 6 is a view of a cryoprobe with an outer sheath and adapter removed. Detailed Description of the Preferred Embodiments Turning now to the drawings, FIG. 1 shows a cryoprobe being used in an endometrial ablation procedure. A cryoprobe 2 is inserted through the vagina and cervix into the uterus 5. Prior to cryotherapy, the uterus is distended with a heat-conducting fluid 7, preferably 10 cc of sterile intrauterine gel. The bladder 10 is filled with approximately 300 to 400 ml of warm sterile saline to act as heat sink to protect it from cryonecrosis. An ultrasound probe 8 is inserted in the rectum 9 to monitor probe placement and ice ball formation. The cryoprobe 2 is optimally placed in the uterine fundus with the distal tip just touching the uterine wall. A freezing cycle is begun so that a temperature of -40° C and below is induced in the diseased tissue. Using the transrectal ultrasound, a clinician monitors the radius of the ice ball until it is approximately 25-50% through the myometrium. At this point, the freeze cycle is discontinued and the ice ball allowed to thaw. A second freezing procedure should be conducted in the fundus using this same procedure. If, however, the length of the endometrial cavity is greater than 6 cm. , the clinician may dislodge the cryoprobe 2 from the latter formed ice ball when the distal tip temperature reaches 0° and pulls the tip into the lower uterine segment in order to freeze the lower uterine segment. When the formed ice ball encompasses the entire endometrial cavity, thawing is initiated for a second time. FIG. 2 shows a cryoprobe 2 according to one embodiment of the invention. A first sheath 20 houses the cryostat 22 described in detail below. A handle 24 of convenient size is provided. The handle 24 houses a high pressure gas supply line 26 and electrical wiring (not shown) . The details of the cryostat 22 used in the cryoprobe 2 are illustrated in FIG. 2 and 3. FIG 2 shows a first embodiment of the cryoprobe 2. The high-pressure gas supply line 26 connects to the proximal extension 28 of the finned tube coiled heat exchanger 30. The heat exchanger 30 extends longitudinally through the first sheath 20 and connects to the distal extension 32 which opens through Joule-Thomson nozzle 34 into expansion chamber 36. The heat exchanger 30 is coiled around mandrel 38 so that the construction known as a Giaque-Hampson heat exchanger is formed. At the distal tip of the mandrel 38 a thermocouple 40 may be provided so that the clinician can monitor the temperature inside the cryoprobe 2. FIG. 2 illustrates a single coiled heat exchanger. Alternatively, FIG. 3 shows a cryoprobe that includes two coiled heat exchangers 40 and 30 and two Joule-Thomson nozzles. This dual helix cryoprobe 45 produces large ice balls. A second high-pressure gas supply line (not illustrated) , heat exchanger 40, and Joule-Thomson nozzle 42 are provided. The helical coils preferably are parallel to each other, meaning that the coils follow the same helical path around the mandrel. As shown in FIG. 3, when the Joule-Thomson nozzles 42 and 34 are located at the same longitudinal location, a large spherical ice ball can be formed very rapidly. When the Joule-Thomson nozzles are offset or staggered, meaning that the longitudinal placement of each nozzle is significantly different, the probe very rapidly forms a cylindrical ice ball. Modifications of the configuration illustrated in FIG. 2 and 3 will create various ice ball shapes. For convenience of reference, we refer to three longitudinal segments of the cryoprobe as LI, L2, and L3. The distance between the Joule-Thomson nozzle and the end of the heat exchanger is denoted L3. The length of the distal extension 32 is denoted L2. The length of the heat exchanger is denoted LI. With LI set at approximately 5 cm, if L2 is approximately 7.5 mm and L3 is approximately 5 mm, a pear ice ball shape may be formed. Alternatively, should an olive shaped ice ball be desired, L3 is shortened to approximately 2.5 mm. Although by varying these three parameters, it is possible to form ice balls of various other shapes, an insulating layer 44 provided on the inner surface of the sheath proximal to the heat exchanger affords even greater ice ball shaping control. FIGs. 2 and 3 illustrate one embodiment of a cryoprobe 2 including an insulating layer 44. A coaxially-disposed inner sheath 28 having a diameter smaller than that of the first sheath 20 forms insulating layer 44. At either end of the inner sheath 28 are distal seal 48 and proximal seal 50 whereby the sheath 20, seals 48 and 50, and inner sheath 28 enclose insulating layer 44. Insulating layer 44 may be comprised simply of air or of another insulating dielectric material. As illustrated in FIGs. 2 and 3, the insulating layer 44 is of a uniform thickness. Alternatively, the insulating layer could be tapered so that the insulation does not begin abruptly at the proximal end of the heat exchanger. This would allow a "feathering" to the proximal edge of the ice ball. Of course, this requires a similar tapering in the diameter of inner sheath 46. By displacing distally or proximally the distal end of the insulating layer 44 as defined by distal seal 48, the ice ball is lengthened or shortened. In addition, the shape of the distal edge of the ice ball may be significantly affected. FIG. 4 illustrates an outer sheath 56 , adapter 58 and pressure sensor port 62 according to one embodiment of the invention. Outer sheath 56 surrounds sheath 30 so that the danger of gas leaks is lessened. In turn, this greatly reduces the risk of gas embolism causing death or trauma to the patient. The danger of gas embolism is particularly acute during endometrial ablation because of the highly vascular nature of the uterus. Outer sheath 56 and sheath 20 define a space 64. Space 64 can be of negligible thickness or greater provided that thermal conductivity between outer sheath 56 and sheath 30 is not negatively affected to the point that therapeutic efficacy is threatened. Filling space 64 with a petroleum jelly or similar heat-conducting fluid enhances the thermal conductivity of space 64. In addition, outer sheath 64 is preferably made of surgical stainless steel so that its thermal conductivity is high. In one embodiment adapter 58 attaches the outer sheath 56 in a sealing arrangement to the handle 24 of the cryoprobe 2. Fig 5 illustrates the outer sheath 56 and adapter 58 removed from the cryoprobe 2. Fig. 6 illustrates how the handle 24 is machined to fit with adapter 58. Crossing through adapter 58 is a channel 60 which ends in pressure sensor port 62 so that pressure sensor port 62 is in fluid communication with space 64. A pressure sensor tube 64 connects to pressure sensor port 62 so that a sensor (not illustrated) remote from the handle can detect gas leaks. Alternatively, the sensor could be located in the handle 24. The sensor may comprise a pressure transducer or a chemical sensor attuned to a particular gas, preferably argon, used as the high-pressure gas. If the sensor detects a gas leak, pumping of the high-pressure gas could be automatically ceased and an alarm given. The clinician could then remove the cryoprobe before any danger of gas embolism. In a basic embodiment, the cryoprobe may simply employ an outer sheath 56 and adapter 58 without the channel 60, pressure port 62 and associated sensor. Although there would be no alarm possible in this embodiment, the patient would still enjoy the added security provided by the outer sheath against gas embolism. Although the outer sheath 56 is particularly useful for endometrial ablation because of the highly vascular nature of the uterus, cryosurgery on other organs in the body will also benefit from the added safety of this invention. Moreover, the benefits provided by the insulating layer whereby the ice ball can lengthened, shortened and distal edge shape affected are not limited to endometrial ablation but can enhance other forms of cryosurgery as well. Thus, while the preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the invention. Other embodiments and configurations may be devised without departing from the spirit of the invention and the scope of the appended claims.

Claims: Claims 1. A cryoprobe comprising : a high pressure gas supply line supplying a Joule- Thomson nozzle; a heat exchanger interposed between the high pressure gas supply line and the Joule-Thomson nozzle; a first sheath containing said heat exchanger and Joule-Thomson nozzle; said sheath having an outer and inner surface; and an insulating layer formed on the inner surface of said first sheath, said insulating layer located proximally with respect to said heat exchanger. 2. The device of claim 1, further comprising: an inner sheath disposed within said first sheath, said inner sheath located proximally with respect to said heat exchanger; a distal seal attached to a distal end of said inner sheath, wherein said distal seal is disposed between said inner sheath and said first sheath; and a proximal seal attached to a proximal end of said inner sheath, wherein said proximal seal is disposed between said inner sheath and said first sheath, and wherein said insulating layer is formed by an insulating space defined by said inner sheath, said first sheath, and said distal and proximal seals. 3. The device of claim 2, wherein said insulating layer comprises air. 4. The device of claim 2, wherein said insulating layer is of a uniform thickness. 5. The device of claim 2, wherein the insulating layer is tapered. 6. A cryoprobe comprising: a high pressure gas supply line supplying a Joule- Thomson nozzle; a heat exchanger interposed between the high pressure gas supply line and the Joule-Thomson nozzle; a first sheath containing said heat exchanger and Joule-Thomson nozzle, said first sheath having an outer surface; a handle attached to said first sheath; and an outer sheath surrounding the outer surface of said first sheath, said outer sheath defining a space between said first sheath and said outer sheath whereby a patient is protected from gas leaks in said first sheath. 7. The cryoprobe of claim 6, further comprising an adapter sealing said outer sheath to said handle. 8. The cryoprobe of claim 7, wherein said adapter defines a channel, said channel having a proximal end connected to a pressure sensor port whereby said pressure sensor port is in fluid communication with the space defined between said first sheath and said outer sheath. 9. The cryoprobe of claim 8, wherein a sensor is in fluid communication with said pressure sensor port. 10. The cryoprobe of claim 9, wherein said sensor comprises a pressure transducer. 11. The cryoprobe of claim 9, wherein said sensor comprises a chemical sensor. 12. The cryoprobe of claim 9, wherein said sensor activates an alarm if a gas leak is sensed. 13. The cryoprobe of claim 8, wherein the space defined by said outer sheath and said first sheath is filled with a heat-conducting fluid. 14. An article of manufacture, comprising: an outer sheath sized to cover a distal portion of a cryoprobe, said outer sheath defining a space between an outer surface of the distal portion of the cryoprobe and said outer sheath; and an adapter associated with a proximal end of said outer sheath whereby said adapter attaches said outer sheath to the cryoprobe. 15. The sheath of claim 14 wherein said adapter defines a channel ending in a pressure sensor port whereby said pressure sensor port is in fluid communication with a space defined by the outer sheath and the outer surface of the distal portion of the cryoprobe. 16. A method of cryosurgery comprising the steps of: providing a sheathed cryoprobe comprising a high- pressure gas supply line supplying a Joule-Thomson nozzle; a heat exchanger interposed between the high-pressure gas supply line and the Joule-Thomson nozzle, a first sheath containing said heat exchanger and said Joule-Thomson nozzle, said first sheath having an outer surface, a handle attached to said first sheath, and an outer sheath surrounding the outer surface of said first sheath, said outer sheath defining a space between said first sheath and said outer sheath; and freezing diseased tissue with the sheathed cryoprobe. AMENDED CLAIMS [received by the International Bureau on 20 October 1999 (20.10.99); original claims 1 -16 replaced by new claims 1-1 1 (3 pages)] 1. A cyroprobe comprising: a high pressure gas supply line supplying a Joule Thomson nozzle; a heat exchanger interposed between the high pressure gas supply line and the Joule-Thomson nozzle; a first sheath containing said heat exchanger and Joule- Thomson nozzle, said first sheath having an outer surface; a handle attached to said first sheath; and an impermeable outer sheath surrounding the outer surface of said first sheath, said outer sheath defining a space between said first sheath and said outer sheath whereby a patient is protected from gas leaks in said first sheath. 2. The cyroprobe of claim 1 further comprising an adapter sealing said outer sheath to said handle. 3. The cyroprobe of claim 2 , wherein said adapter defines a channel, said channel having a proximal end connected to a pressure sensor port whereby said pressure sensor port is in fluid communication with the space defined between said first sheath and said outer sheath. 4. The cyroprobe of claim 3, wherein a sensor is in fluid communication with said pressure sensor port. 5. The cyroprobe of claim 4 , wherein said sensor comprises a pressure transducer. 6. The cyroprobe of claim 4, wherein said sensor comprises a chemical sensor. 7. The cyroprobe of claim 4, wherein said sensor activates an alarm if a gas leak is sensed. 8. The cyroprobe of claim 3 , wherein the space defined by said outer sheath and said first sheath is filled with a heat-conducting fluid. 9. An article of manufacture, comprising: an impermeable outer sheath sized to cover a distal portion of a cyroprobe; and an adapter associated with a proximal end of said outer sheath whereby said adapter is adapted to attach said outer sheath to the cyroprobe . 10. The sheath of claim 9 wherein said adapter defines a channel ending in a pressure sensor port whereby said pressure sensor port is in fluid communication with a space defined by the outer sheath and the outer surface of the distal portion of the cyroprobe if said adapter is attached to the cyroprobe. 11. A method of cyrosurgery comprising the steps of: providing a sheathed cyroprobe comprising a high- pressure gas supply line supplying a Joule-Thomson nozzle; a heat exchanger interposed between the high-pressure gas supply line and the Joule-Thomson nozzle, a first sheath containing said heat exchanger and said Joule-Thomson nozzle, said first sheath having an outer surface, a handle attached to said first sheath, and an outer sheath surrounding the outer surface of said first sheath, said outer sheath defining a space between said first sheath and said outer sheath; and freezing diseased tissue with the sheathed cyroprobe .

Inventors: EUM JAY J, MIKUS PAUL W, EUM, JAY, J., MIKUS, PAUL, W.
Applicants: ENDOCARE INC, ENDOCARE, INC.
Application year: 1999
Main classification: A61B17
IPC codes: A61B18