Quantitative echography: a potential control technique for cryosurgery

An issue of major interest in cryosurgery is the extent of the frozen tissue boundary during the freezing process and of cryonecrosis in the post-freezing period. These problems have to be solved to use cryosurgery as a controlled therapeutic method. The answer can either be found invasively with thermocouples embedded in the tissue, or noninvasively by tissue electric impedance monitoring, which does not give the depth of the frozen tissue boundary. Neither method is actually satisfactory. Ultrasound and echographic techniques are proposed as quantitative noninvasive techniques to determine in real time the extent of the frozen tissue boundary and to follow the kinetics of the advancing cold front at any time during the freezing process