Abstract: A miniature refrigeration system and method of operation. A primary refrigerant is pressurized by a compressor to a relatively low pressure, for safety reasons. The compressed primary refrigerant is passed through a primary-to-secondary heat exchanger, to precool the gas mixture. The secondary side of the primary-to-secondary heat exchanger is cooled by a secondary refrigeration system. The primary refrigerant exiting the primary outlet of the primary-to-secondary heat exchanger passes to a primary Joule-Thomson expansion element where the high pressure gas is expanded to a lower temperature. This low temperature gas cools a heat transfer element mounted in the outer wall of the catheter or cryoprobe, to cool surrounding tissue. Return gas can flow back through a distal primary-to-primary heat exchanger to further cool the incoming high pressure gas mixture. A proximal primary-to-primary heat exchanger can be added between the primary-to-secondary heat exchanger and the primary compressor.

Abstract: A sheath for use on a closed loop Joule-Thomson cryosurgical probe, and the combination of the and the closed loop probe. The sheath is slipped over the probe, thereby separating the probe from the environment. The sheath has a grip which fits over the handle of the cryosurgical probe, and an extendible shroud which can be longitudinally extended to cover tubing and which are attached to the handle. The sheath has a hollow multi-lumen catheter shaped and sized to fit snugly over the cannula of the cryosurgical probe. The catheter is not thermally conductive, preventing transfer of heat from the ambient to the gas mixture, and preventing the freezing of tissues at undesired locations along the catheter. A thermally conductive cap or tip is attached to the distal end of the hollow catheter. The thermally conductive cap or tip fits snugly over the cold tip on the probe, and it efficiently transfers heat from the target tissue to the cold tip, which in turn transfers heat to the expanded gas mixture.

Abstract: A sheath for use on a closed loop Joule-Thomson cryosurgical probe, and the combination of the and the closed loop probe. The sheath is slipped over the probe, thereby separating the probe from the environment. The sheath has a grip which fits over the handle of the cryosurgical probe, and an extendible shroud which can be longitudinally extended to cover tubing and which are attached to the handle. The sheath has a hollow multi-lumen catheter shaped and sized to fit snugly over the cannula of the cryosurgical probe. The catheter is not thermally conductive, preventing transfer of heat from the ambient to the gas mixture, and preventing the freezing of tissues at undesired locations along the catheter. A thermally conductive cap or tip is attached to the distal end of the hollow catheter. The thermally conductive cap or tip fits snugly over the cold tip on the probe, and it efficiently transfers heat from the target tissue to the cold tip, which in turn transfers heat to the expanded gas mixture.

Abstract: A sheath for use on a closed loop Joule-Thomson cryosurgical probe, and the combination of the and the closed loop probe. The sheath is slipped over the probe, thereby separating the probe from the environment. The sheath has a grip which fits over the handle of the cryosurgical probe, and an extendible shroud which can be longitudinally extended to cover tubing and which are attached to the handle. The sheath has a hollow multi-lumen catheter shaped and sized to fit snugly over the cannula of the cryosurgical probe. The catheter is not thermally conductive, preventing transfer of heat from the ambient to the gas mixture, and preventing the freezing of tissues at undesired locations along the catheter. A thermally conductive cap or tip is attached to the distal end of the hollow catheter. The thermally conductive cap or tip fits snugly over the cold tip on the probe, and it efficiently transfers heat from the target tissue to the cold tip, which in turn transfers heat to the expanded gas mixture.

Abstract: A miniature refrigeration system and method of operation. A primary refrigerant is pressurized by a compressor to a relatively low pressure, for safety reasons. The compressed primary refrigerant is passed through a primary-to-secondary heat exchanger, to precool the gas mixture. The secondary side of the primary-to-secondary heat exchanger is cooled by a secondary refrigeration system. The primary refrigerant exiting the primary outlet of the primary-to-secondary heat exchanger passes to a primary Joule-Thomson expansion element where the high pressure gas is expanded to a lower temperature. This low temperature gas cools a heat transfer element mounted in the outer wall of the catheter or cryoprobe, to cool surrounding tissue. Return gas can flow back through a distal primary-to-primary heat exchanger to further cool the incoming high pressure gas mixture. A proximal primary-to-primary heat exchanger can be added between the primary-to-secondary heat exchanger and the primary compressor.

Abstract: A disposable, sterilizable sheath for use on a closed loop Joule-Thomson cryosurgical probe, and the combination of the disposable sheath and the closed loop probe. The sheath is slipped over the probe, thereby separating the probe from the environment. The sheath has a grip which fits over the handle of the cryosurgical probe, and an extendible shroud which can be longitudinally extended to cover tubing and which are attached to the handle. The sheath has a hollow multi-lumen catheter shaped and sized to fit snugly over the cannula of the cryosurgical probe. The catheter is not thermally conductive, preventing transfer of heat from the ambient to the gas mixture, and preventing the freezing of tissues at undesired locations along the catheter. A thermally conductive cap or tip is attached to the distal end of the hollow catheter.

Abstract: A miniature mixed gas refrigeration system and method of operation are disclosed. An optimum gas mixture is formulated from a group of component fluids, according to calculated thermodynamic properties of a group of candidate fluid mixtures. The gas mixture is pressurized by a compressor to a pressure less than 420 psia, for safety reasons. The compressed gas mixture is passed through a primary heat exchanger, and then through a primary-to-secondary heat exchanger, to precool the gas mixture. The secondary side of the primary/secondary heat exchanger is cooled by a secondary Joule-Thomson refrigeration system. Properly sized flow restrictions in the primary side of the primary/secondary heat exchanger can solidify and trap liquid contaminants that may be in the gas mixture. The gas mixture exiting the primary outlet of the primary/secondary heat exchanger passes to a primary Joule-Thomson expansion element where the high pressure gas is expanded isenthalpically to a lower temperature at least as low as 183K.