February 1997
P. Mikus, J. Eum, G. Kelly, R. Brady, D. Reed, D. Le, and Z. Chang
ENDOcare Inc., 18 Technology Drive, Suite 134, irvine, CA 92618

The progress in minimally invasive cryosurgical procedure is partially attributable to the technical advancement in multiple cryosurgical instrumentation. The recent success in developing an argon-liquidation based cryosurgical system (CRYOcare System) represents a new generation of state-of-the-art cryosurgical devices that will help to bring minimally invasive cryosurgery to the next level. The new device is featured with eight (8) independant controllable cryoprobe channels with the thermocouple being directly mounted inside the tips of cryoprobes (2-mm, 3-mm, 5-mm, and 8-mm). The effective liquidation of argon gas inside the cryoprobe tip drastically improves the cryoprobe performance, reduces the size and simplifies the design of the overall system. Compared to other cryosurgical devices, the argon-liquidation based multiprobe system is particularly marked for a 3-mm cryoprobe. The cryoprobe performance, measured by cool-down time, ice ball size and shape and temperature profile, is highly consistent, uniform and predictable. Additionally, there is no statistically significant difference in performance among the eight (8) cryoprobe channels. In a gelatin solution, an ice ball of approximatley 30 mm in diameter (40 grams) is formed by a 3-mm cryoprobe after 5 minutes, or 40 mm (75 grams) after 10 minutes or 45 mm (110 grams) after 15 minutes and 52mm (146 grams) after 20 minutes freezing. The overall freezing power of a 3-mm cryoprobe is estimated to be 40 watts. Because the refrigerative power is generated in the distal tip, a high quality of thermal insulation is achieved along the shaft without applying major thermal insulation technique. The argon liquidation technique also makes it possible to construct a cryoprobe smaller than 2-mm in diameter over an extended length.

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