| 摘要 |
An improved method for cooling a probe tip of a cryosurgical instrument is provided by supplying a two phase refrigerant comprising a gaseous phase and a liquid phase to a restricted orifice adjacent an expansion chamber of the instrument, conveying the refrigerant through said orifice into said expansion chamber for expanding the gaseous phase into the chamber thereby providing a Joule-Thomson refrigeration effect and for providing additional cooling of the chamber by the evaporation of the liquid phase therein, and, conveying an effluent gas of the expansion chamber to atmosphere. A cryosurgical instrument comprises an expansion chamber formed of a high thermal conductivity material having an outer surface thereof which is adapted for contacting body tissue which is to be treated, a means for conveying a gaseous refrigerant from a source thereof to said expansion chamber, said means including a stationary body forming an orifice of fixed dimensions through which said gas expands into said chamber for cooling said chamber, and, a means for exhausting said gas to atmosphere, said exhaust means including a flow channel communicating between said chamber and a quick acting flow valve, said valve biased for interrupting a flow path through the valve between said exhaust conduit and atmosphere and selectively operable to establish the flow path through the valve.
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