Patent ID: 7083612

Claim:
A cryotherapy system comprising: a plurality of cryoprobes, each such cryoprobe having a shaft with a closed distal end adapted for insertion into a body and conduits for flowing a cryogenic fluid through the shaft to reduce a temperature of the distal end; a source of the cryogenic fluid; a plurality of flow-control metering valves in fluid communication with the conduits of the plurality of cryoprobes and with the source of the cryogenic fluid; a compressor in fluid communication with the conduits of the plurality of cryoprobes to define a self-contained fluid system; and a computer processor comprising: instructions to control the plurality of flow-control metering valves and the compressor to provide desired flows of the cryogenic fluid through the conduits of the self-contained fluid system; and instructions to control the compressor and the plurality of flow-control metering valves to provide an initial flow of the cryogenic fluid through the conduits of the cryoprobes under physical conditions near a critical point of a liquid-vapor system for the cryogenic fluid, wherein the critical point defines a point in a phase diagram of the liquid-vapor system where molar volumes are substantially equivalent for liquid and gas, whereby vapor lock associated with freezing of the cryoprobes is avoided.