Development of a microprocessor controlled cryosurgical system

This paper presents the development of a microprocessor controlled cryosurgical system optimized for dermatologic cryosurgery. The cryosurgical system was developed to provide the user with the accurate control of the three critical parameters of cryosurgery; rate of freeze, duration of ice ball formation, and rate of tissue thaw. The design, based on the Joule-Thompson principle, provides accurate control of the high-pressure nitrous oxide gas, and demonstrates two distinct advantages not currently available with the traditional liquid nitrogen systems. The first is a user defined temperature selection, which allows the clinical practitioner to select the optimal probe temperature for specific cases, and the second is the inclusion of predefined tissue thaw cycles that will provide increased tissue destruction over the currently used spontaneous thaw practice. Design for this instrument was based on physiologic properties obtained from clinical and tissue modeling studies. Cryo-system theory and resources provided by MIRA, Inc. (Uxbridge, Massachusetts) also provided the basis for the development of this system.