A study of the heating effect on mouse liver after Cryosurgery

Cryosurgery is used as a treatment method for warts and malignant tumors which is an operation method that uses vital reaction of tissue by applying the effect of low temperature. Since liquid nitrogen and argon gas are applied as cryogen, it is therefore difficult to control the temperature precisely. It is possible to destroy the tumors by hyperthermia, but there are few studies including warming condition higher than body temperature after cryosurgery. The aim is to produce cryosurgery-hyperthermia system and to evaluate the ability of this system and hyperthermia condition after cryosurgery by studying the effect of cryosurgery-hyperthermia in mice livers. Contact type cryosurgical system in this study includes Free Piston Stirling Cooler (FPSC) and Peltier device, using 1cycle method of fast freezing and slow thawing only. Contact probe can be used for freezing, thawing and heating. Temperatures of tissue surface and probe are measured by K-type thermocouples. Mice liver after operation were stained by Hematoxylin-Eosin (HE) and observed under optical microscope. The result showed measured temperatures of heating tissue following cryosurgery, and stained tissue showed necrosis. This suggests the possibility of electrical temperature control during cryosurgery and the effect of hyperthermia after cryosurgery would supply a more effective treatment system. Now we are looking into the possibility of developing an insertion type of cryosurgical system over the contact type. This possible method may contribute to cryosurgery in the future.