Abstract:
A cryosurgical system and related methods of utilizing distinct freeze and thaw fluids to selectively freeze or thaw tissue as part of a cryosurgical treatment plan. A closed loop cryosurgical system can include a control console, a cryocooler, a freeze tank, a thaw tank as well as fluid supply and fluid return lines operably interconnecting one or more cryoprobes with the freeze and thaw tank. At the direction of the control console, the cryocooler is used to cool a freeze fluid in the freeze tank while a heating element in the thaw tank is used to head a thaw fluid in the thaw tank. By using distinctly controlled reservoirs of freeze and thaw fluid, the cryosurgical system is able to quickly cycle back and forth between freeze and thaw cycles conducted as part of a cryosurgical treatment.

Description:
PRIORITY CLAIM 
       [0001]    The present application claims priority to U.S. Provisional Application Ser. No. 60/865,524, filed Nov. 13, 2006 and entitled “CLOSED LOOP CRYOSURGICAL SYSTEM”, which is herein incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present disclosure is directed toward cryoablation treatment of the prostate. In particular, the present disclosure is directed to a cryosurgical system utilizing distinct freeze and thaw fluids for selectively freezing or thawing prostate tissue as part of cryosurgical treatment plan. 
       BACKGROUND OF THE INVENTION 
       [0003]    Cryoablation of the prostate involves controlled freezing of portions of the prostate to selectively kill cancerous tissue as well as the connective tissue and capillaries surrounding the cancerous tissue. When exposed to freezing, the cancerous cells are destroyed while the destruction of the surrounding connective tissue and capillaries prevents and/or inhibits any additional growth of the cancerous tissue. Cryosurgical probes quickly freeze diseased body tissue, causing the tissue to die after which it will be absorbed by the body, expelled by the body, sloughed off or replaced by scar tissue. In addition to treatment of the prostate, cryoablation has been used successfully in a variety of gynecological applications as well as for treatment of a number of other diseases and conditions including breast cancer, liver cancer, renal cancer glaucoma and other eye diseases. 
         [0004]    A variety of cryosurgical instruments variously referred to as cryoprobes, cryosurgical probes, cryosurgical ablation devices, cryostats and cryocoolers have been used as patient interfaces during cryosurgery. These devices typically use the principle of Joule-Thomson expansion to generate cooling. The devices take advantage of the fact that most fluids, when rapidly expanded, become extremely cold. In these devices, a high pressure gas mixture is expanded through a nozzle inside a small cylindrical shaft or sheath typically made of steel. The Joule-Thomson expansion cools the steel sheath to a cold temperature very rapidly. The cryosurgical probes then form ice balls which freeze diseased tissue. A properly performed cryosurgical procedure allows cryoablation of the diseased tissue without undue destruction of surrounding healthy tissue. 
       SUMMARY OF THE INVENTION 
       [0005]    The present disclosure is directed to a cryosurgical system and related methods of utilizing distinct freeze and thaw fluids to selectively freeze or thaw tissue as part of a cryosurgical treatment plan. A closed loop cryosurgical system can comprise a control console, a cryocooler, a freeze tank, a thaw tank as well as fluid supply and fluid return lines operably interconnecting one or more cryoprobes with the freeze and thaw tank. At the direction of the control console, the cryocooler is used to cool a freeze fluid in the freeze tank while a heating element in the thaw tank is used to heat a thaw fluid in the thaw tank. By using distinctly controlled reservoirs of freeze and thaw fluid, the cryosurgical system is able to quickly cycle back and forth between freeze and thaw cycles conducted as part of a cryosurgical treatment. 
         [0006]    In one aspect, the present disclosure is directed to a cryosurgical system having distinct reservoirs of freeze and thaw fluids that are monitored and adjusted by a control console. The freeze and thaw fluids can be selectively routed through one or more cryoprobes to conduct ablation and thaw cycles during a cryosurgical treatment, i.e., each cryoprobe is controlled independently from the others. 
         [0007]    In another aspect, the present disclosure is directed to a method for conducting a cryosurgical treatment wherein distinct freeze and thaw fluids are monitored and adjusted such that the freeze and thaw fluids can be directed through one or more cryoprobes to conduct freeze and thaw portions of the cryosurgical treatment. 
         [0008]    The above summary of the various representative embodiments of the invention is not intended to describe each illustrated embodiment or every implementation of the invention. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the invention. The figures in the detailed description that follows more particularly exemplify these embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0009]    These as well as other objects and advantages of this invention, will be more completely understood and appreciated by referring to the following more detailed description of the presently preferred exemplary embodiments of the invention in conjunction with the accompanying drawings of which: 
           [0010]      FIG. 1  is a schematic illustration of an embodiment of a closed loop cryosurgical system according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Referring to  FIG. 1 , there can be seen an embodiment of a closed loop cryosurgical system  100  according to the present disclosure. Cryosurgical system  100  generally includes a control console  102  operably interconnected with a cryocooler  104  and a heating element  106 . An exemplary control console  102  that may be used with an embodiment of the present invention is used as part of the Her Option® Office Cryoablation Therapy available from American Medical Systems of Minnetonka, Minn. Console  102  can include controls that allow for monitoring, activation, deactivation, and modification of various system parameters, such as the flow rates, pressures, and temperatures of the refrigerants. In addition, console  102  can include a display that allows the operator to quickly monitor, and in some embodiments adjust, the performance of cryosurgical system  100 . 
         [0012]    In one representative embodiment, cryocooler  104  can comprise a dual-stage compressor system with a primary compressor providing a primary pressurized, mixed gas refrigerant and a secondary compressor providing a secondary pressurized, mixed gas refrigerant. Through the use of a dual-stage compressor system, cryocooler  104  can achieve cooler temperatures than a single stage compressor system. In addition, the use of gas mixtures for the primary pressurized, mixed gas refrigerant and secondary pressurized, mixed gas refrigerant are known in the art that provide a dramatic increase in cooling performance over a single gas. 
         [0013]    Referring again to  FIG. 1 , cryosurgical system further comprises a freeze tank  107 , a thaw tank  108  and a plurality of cryoprobes  110   a ,  110   b  and  110   c . Cryoprobes  110   a ,  110   b  and  110   c  are fluidly interconnected to the freeze tank  107  and thaw tank  108  with supply fluid lines  112   a ,  112   b  and  112   c  and return fluid lines  114   a ,  114   b ,  114   c . The supply fluid lines  112   a ,  112   b ,  112   c  and return fluid lines  114   a ,  114   b ,  114   c  are generally flexible to allow for easy manipulation and placement of cryoprobes  110   a ,  110   b  and  110   c . In addition, supply fluid lines  112   a ,  112   b  and  112   c  and return fluid lines  114   a ,  114   b ,  114   c  can be insulated so as to limit heat transfer with the ambient environment and prevent medical professional from being exposed to potentially uncomfortable or unsafe temperatures. 
         [0014]    Supply fluid lines  112   a ,  112   b  and  112   c  each comprise an ablation supply portion  116   a ,  116   b ,  116   c , a thaw supply portion  118   a ,  118   b ,  118   c  and a cryoprobe supply portion  120   a ,  120   b ,  120   c  while return fluid lines  114   a ,  114   b ,  114   c  comprise an ablation return portion  122   a ,  122   b ,  122   c , a thaw return portion  124   a ,  124   b ,  124   c  and a cryoprobe return portion  126   a ,  126   b ,  126   c . Each of the ablation supply portions  116   a ,  116   b ,  116   c  and thaw supply portions  118   a ,  118   b ,  118   c  include a supply valve  128  while each of the ablation return portions  122   a ,  122   b ,  122   c  and thaw return portions  124   a ,  124   b ,  124   c  include a return valve  130 . Supply valve  128  and return valve  130  can comprise suitable manual valve or remotely actuated, automated valves. In one representative embodiment, the supply and return valves can comprise solenoid valves that are operably interconnected with the control console  102  such that actuation of each valve is independently controlled by the control console  102 . In addition, each of the cryoprobe supply portions  120   a ,  120   b ,  120   c  includes a cryoprobe supply pump  132 . 
         [0015]    Freeze tank  107  and thaw tank  108  generally comprise sealed and insulated tanks fabricated of materials suitable for use with extreme cold temperatures as well as elevated temperatures. Freeze tank  107  includes a cooling heat exchanger  133  that is operably interconnected to the cryocooler  104 . Freeze tank  107  includes a reservoir of an ablation fluid  134  and the thaw tank includes a reservoir of a thaw fluid  136 . Ablation fluid  134  and thaw fluid  136  can comprise any suitable heat exchange fluid wherein ablation fluid  134  has desirable freeze properties and thaw fluid  136  has desirable boiling properties. In some instances, ablation fluid  134  and thaw fluid  136  can comprise the same fluid as long as the freezing and boiling properties are suitable for the desired temperature operation range of the cryosurgical system  100 . Representative heat exchange fluids can comprise perfluorocarbon (PFC) fluids as well as Asahikling 225 (AK-225) commercially available from the Asahi Glass Company. When ablation fluid  134  and thaw fluid  136  comprise the same fluid, an exchange line  138  can operably, fluidly connect the freeze tank  107  and thaw tank  108 . Exchange line  138  can comprise an exchange valve  140  for isolating the freeze tank  107  and thaw tank  108  during a cryosurgical treatment. Both freeze tank  107  and thaw tank  108  can also comprise temperature control sensors  142  operably connected to the control console  102 . 
         [0016]    Cryoprobes  110   a ,  110   b  and  110   c  can comprise any of a variety of different cryoprobes selected based upon the cryosurgical treatment to be performed. In some representative embodiments, cryoprobes  110   a ,  110   b ,  110   c  can be rigid or flexible, straight or curved, long or short and the like. Furthermore, cryoprobes  110   a ,  110   b ,  110   c  can be selected for specific cryosurgical treatment applications including, for example, urethra treatment, prostate treatment, bladder treatment and ureter/kidney treatment. Although not presently illustrated, it will be understood that cryosurgical system  100  can further comprise additional components for assisting with the maintenance and positioning of cryoprobes  110   a ,  110   b  and  110   c . In some embodiments, cryoprobes  110   a ,  110   b ,  110   c  can include temperature sensors that are in operable communication with the control console  102  for monitoring and controlling cryoprobe temperature during treatment. For instance, the supply fluid lines  112   a ,  112   b ,  112   c , return fluid lines  114   a ,  114   b ,  114   c  and cryoprobes  110   a ,  110   b ,  110   c  connect to the freeze tank  107  and thaw tank  108  by way of an articulating arm, which may be manually or automatically used to position the cryostats  110   a ,  110   b ,  110   c . In some embodiments, the articulating arm may incorporate the supply fluid lines  112   a ,  112   b ,  112   c  and return fluid lines  114   a ,  114   b ,  114   c  within the articulating arm. In addition, the cryosurgical system can further include a positioning grid to properly align and position the cryoprobes  110   a ,  110   b  and  110   c  for patient insertion. 
         [0017]    In use, a medical professional determines the desired operating conditions of the cryosurgical system  100  and inputs them into the control console  102 . In general, a cryosurgical treatment will consist of at least one cryoablation cycle. Frequently, the cryosurgical treatment will include several distinct cryoablation cycles with a thaw cycle occurring between each cryoablation cycle, wherein one or more cryoprobes are operated independently in a simultaneous or sequential manner as appropriate to the application. 
         [0018]    During a first cryoablation cycle, the control console activates the cryocooler  104  such that the freeze tank  107  can be cooled. In the case of cryocooler  104  comprising a dual-stage compressor system, a primary mixed gas refrigerant is used to cool a secondary mixed gas refrigerant, which is subsequently pumped through the cooling heat exchanger  133 . As the secondary mixed gas refrigerant passes through the cooling heat exchanger  133 , heat energy is transferred from the ablation fluid  134  into the secondary mixed gas refrigerant such that over a relatively short period of time, the temperature of the ablation fluid  134  approaches the incoming temperature of the secondary mixed gas refrigerant. Once the ablation fluid  134  reaches the desired ablation temperature as measured by the temperature control sensor  142 , ablation fluid  134  is ready to supply one or more of the cryoprobes  110   a ,  110   b ,  110   c.    
         [0019]    For purposes of describing use of the cryosurgical system  100 , the use of cryoprobe  110   a  will be described though it is to be understood that the same principles of operation apply to the use of cryoprobes  110   b  and  110   c  as well. When the medical professional is ready to utilize cryoprobe  110   a  during an ablation cycle, the supply valves  128  within the ablation supply portion  112   a  and ablation return portion  122   a  are opened while the supply valves  128  within the thaw supply portion  118   a  and the thaw return portions  124   a  are maintained in a closed position. Next, the cryoprobe supply pump  132  within the cryoprobe supply portion  120   a  is actuated such that ablation fluid  134  is pumped through the supply fluid line  112   a  and into the cryoprobe  110   a . Within the cryoprobe  110   a , the ablation fluid  134  flows into a Joule-Thompson expansion element, such as a valve, orifice, or other type of flow constriction, located near the tip of the cryoprobe  110   a , where the ablation fluid  134  is expanded isenthalpically to a lower temperature. A typical Joule-Thompson expansion element is a capillary tube. The ablation fluid  134  then cools a heat transfer element mounted in the wall of the cryoprobe  110   a  so at to form ice ball at the tip of the cryoprobe  110   a  that is used to freeze diseased tissue. The ablation fluid  134  then returns to the freeze tank  107  through the cryoprobe return portion  126  and the ablation return portion  122   a . The ablation fluid  134  then returns to the freeze tank  107  where its temperature is again lowered by exposure to the cooling heat exchanger  133 . 
         [0020]    Following the ablation cycle, the control console activates the heating element  106  to begin warming the thaw fluid  136  within the thaw tank  108 . Heating element  106  can comprise a resistive heating element wherein current supplied to the heating element  106  is converted to heat energy used to heat the thaw fluid  136 . Using temperature control sensor  142 , the control console  102  monitors and controls the operation of the heating element  106  such that the thaw fluid  136  reaches and is maintained at a desired temperature. 
         [0021]    When the medical professional is ready to utilize cryoprobe  110   a  during the thaw cycle, the supply valves  128  within the thaw supply portion  118   a  and thaw return portion  124   a  are opened while the supply valves  128  within the ablation supply portion  116   a  and the ablation return portion  124   a  are closed. Once again, the cryoprobe supply pump  132  within the cryoprobe supply portion  120   a  is actuated such that the thaw fluid  136  is pumped through the cryoprobe supply portion  120   a  and into the cryoprobe  110   a . Within the cryoprobe  110   a , the thaw fluid  136  warms the heat transfer element mounted in the wall of the cryoprobe  110   a  so at to melt the ice ball at the tip of the cryoprobe  110   a  and eventually thaw the previously frozen tissue. This allows the tip of the cryoprobe  110   a  to be removed from the tissue without causing further damage to healthy tissue. The thaw fluid  136  then returns to the thaw tank  108  through the cryoprobe return portion  126   a  and the thaw return portion  124   a . The thaw fluid  136  returns to that tank  108  where its temperature is again increased by exposure to the heating element  106 . Upon completion of a thaw cycle, cryoprobe  110   a  can be removed from the treatment area if treatment is complete or alternatively, the medical professional can commence a new freeze cycle. 
         [0022]    As will be understood by one of skill in the art, cryosurgical system  100  can comprise a variety of physical configurations wherein various components can be grouped together to form combined units or distinct portions of the overall system. For example, cryosurgical system  100  can take the form of a cabinetized or skid-mounted assembly wherein the major components including the control console  102 , cryocooler  104 , freeze tank  107 , and thaw tank  108  are assembled and packaged as a single, unitized assembly. Alternatively, the cryosurgical system  100  can comprise a plurality of distinct assemblies such as, for example, an assembly comprising the control console  102  and cryocooler  104  and a second assembly comprising the freeze tank  107  and thaw tank  108 . 
         [0023]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it will be apparent to those of ordinary skill in the art that the invention is not to be limited to the disclosed embodiments. It will be readily apparent to those of ordinary skill in the art that many modifications and equivalent arrangements can be made thereof without departing from the spirit and scope of the present disclosure, such scope to be accorded the broadest interpretation of the appended claims so as to encompass all equivalent structures and products.