Abstract: A method for subcooling liquid cryogen that is used by a cutting tool uses the steps of dividing liquid phase cryogen between a subcooler feed line and tool feed line. The cryogen in the subcooler feed line is expanded to lower the pressure and decrease the temperature of the cryogen, and the expanded liquid cryogen from the subcooler feed line is added to the interior of a subcooler. A heat exchanger is positioned in the subcooler in contact with the expanded liquid cryogen. The cryogen in the tool feed line is subcooled below its saturation temperature by passing the cryogen through the heat exchanger, and the subcooled cryogen from the heat exchanger is supplied to the cutting tool. As a result, the subcooled cryogen supplied to the cutting tool is substantially 100% liquid cryogen without any vapor content.

Abstract: A method for subcooling liquid cryogen that is used by a cutting tool uses the steps of dividing liquid phase cryogen between a subcooler feed line and tool feed line. The cryogen in the subcooler feed line is expanded to lower the pressure and decrease the temperature of the cryogen, and the expanded liquid cryogen from the subcooler feed line is added to the interior of a subcooler. A heat exchanger is positioned in the subcooler in contact with the expanded liquid cryogen. The cryogen in the tool feed line is subcooled below its saturation temperature by passing the cryogen through the heat exchanger, and the subcooled cryogen from the heat exchanger is supplied to the cutting tool. As a result, the subcooled cryogen supplied to the cutting tool is substantially 100% liquid cryogen without any vapor content.

Abstract: An apparatus and method for automatic operation of a refrigeration system to provide refrigeration power to a catheter for tissue ablation or mapping. The primary refrigeration system can be open loop or closed loop, and a precool loop will typically be closed loop. Equipment and procedures are disclosed for bringing the system to the desired operational state, for controlling the operation by controlling refrigerant flow rate, for performing safety checks, and for achieving safe shutdown. The catheter-based system for performing a cryoablation procedure uses a precooler to lower the temperature of a fluid refrigerant to a sub-cool temperature (?40° C.) at a working pressure (400 psi). The sub-cooled fluid is then introduced into a supply line of the catheter. Upon outflow of the primary fluid from the supply line, and into a tip section of the catheter, the fluid refrigerant boils at an outflow pressure of approximately one atmosphere, at a temperature of about ?88° C.

Abstract: A system for detecting leaks and occlusions in a cryoablation catheter requires monitoring pressure in the catheter at the end of two predetermined time intervals. The catheter includes a catheter tube, a cryo-chamber at the distal end of the catheter, and a supply line for introducing fluid refrigerant into the cryo-chamber. Also included is a pressure sensor mounted in the cryo-chamber for measuring a tip pressure. During the first time interval, fluid refrigerant is prevented from flowing through the catheter while the catheter is evacuated by a vacuum pump. The tip pressure is then measured to detect leaks. During the second time interval, fluid refrigerant is introduced into the cryo-chamber while evacuation continues, and the tip pressure is measured to detect occlusions.

Abstract: A catheter-based system for performing a cryoablation procedure uses a precooler to lower the temperature of a fluid refrigerant to a sub-cool temperature (?40° C.) at a working pressure (400 psi). The sub-cooled fluid is then introduced into a supply line of the catheter. Upon outflow of the primary fluid from the supply line, and into a tip section of the catheter, the fluid refrigerant boils at an outflow pressure of approximately one atmosphere, at a temperature of about ?88° C. In operation, the working pressure is computer controlled to obtain an appropriate outflow pressure for the coldest possible temperature in the tip section.

Abstract: A system for detecting leaks and occlusions in a cryoablation catheter requires monitoring pressure in the catheter at the end of two predetermined time intervals. The catheter includes a catheter tube, a cryo-chamber at the distal end of the catheter, and a supply line for introducing fluid refrigerant into the cryo-chamber. Also included is a pressure sensor mounted in the cryo-chamber for measuring a tip pressure. During the first time interval, fluid refrigerant is prevented from flowing through the catheter while the catheter is evacuated by a vacuum pump. The tip pressure is then measured to detect leaks. During the second time interval, fluid refrigerant is introduced into the cryo-chamber while evacuation continues, and the tip pressure is measured to detect occlusions.

Abstract: MRI system 10 is provided. The MRI system 10 includes a magnet assembly 12. A first cryogen cooling fluid 20 is utilized to cool the magnet assembly 12. A first supply line 16 communicates the first cryogen cooling fluid 20 to the magnet assembly 12. A first return line 18 communicates the first cryogen cooling fluid 20 away from the magnet assembly 12. A blower assembly 22 is positioned between and in communication with the first supply line 16 and the first return line 18. A regenerative heat exchanger 36 is in communication with the first supply line 16 and the first return line 18. The regenerative heat exchanger 36 transfers thermal energy 29 from the first supply line 16 to the first return line 18. The regenerative heat exchanger 36 is positioned between the blower assembly 22 and the magnet assembly 12. A second supply line 28 transports a second cryogen fluid 26 through a pre-cooler assembly 24.

Abstract: MRI system 10 is provided. The MRI system 10 includes a magnet assembly 12. A first cryogen cooling fluid 20 is utilized to cool the magnet assembly 12. A first supply line 16 communicates the first cryogen cooling fluid 20 to the magnet assembly 12. A first return line 18 communicates the first cryogen cooling fluid 20 away from the magnet assembly 12. A blower assembly 22 is positioned between and in communication with the first supply line 16 and the first return line 18. A regenerative heat exchanger 36 is in communication with the first supply line 16 and the first return line 18. The regenerative heat exchanger 36 transfers thermal energy 29 from the first supply line 16 to the first return line 18. The regenerative heat exchanger 36 is positioned between the blower assembly 22 and the magnet assembly 12. A second supply line 28 transports a second cryogen fluid 26 through a pre-cooler assembly 24.

Abstract: A catheter-based system for performing a cryoablation procedure uses a precooler to lower the temperature of a fluid refrigerant to a sub-cool temperature (−40° C.) at a working pressure (400 psi). The sub-cooled fluid is then introduced into a supply line of the catheter. Upon outflow of the primary fluid from the supply line, and into a tip section of the catheter, the fluid refrigerant boils at an outflow pressure of approximately one atmosphere, at a temperature of about −88° C. In operation, the working pressure is computer controlled to obtain an appropriate outflow pressure for the coldest possible temperature in the tip section.

Abstract: A catheter-based system for performing a cryoablation procedure uses a precooler to lower the temperature of a fluid refrigerant to a sub-cool temperature (?40° C.) at a working pressure (400 psi). The sub-cooled fluid is then introduced into a supply line of the catheter. Upon outflow of the primary fluid from the supply line, and into a tip section of the catheter, the fluid refrigerant boils at an outflow pressure of approximately one atmosphere, at a temperature of about ?88° C. In operation, the working pressure is computer controlled to obtain an appropriate outflow pressure for the coldest possible temperature in the tip section.