Ultrasonic monitoring of cryotherapy: Results on in vitro skin of domestic pig

Ultrasound and echographic techniques are proposed as a non-invasive monitoring technique for cryosurgery. Our goal is 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. In this paper we describe the experimental results of cryotherapy monitoring with a 15 MHz transducer in in vitro skin of domestic pig. We show that it is possible to detect the frozen region depth boundary. Kinetics of the freeze-thaw cycle is also measurable (thickness of the frozen region versus time), which is of major importance as it allows to exactly adjust the freezing time as a function of the tumor depth extent.