Standardization of cryosurgical lesions

In order to establish treatment standards for tumours of various types and sizes, one must have full control over the cryosurgical operation. The requirements for such controlled cryotherapy are discussed, and it is argued that it should be possible to keep the freezing rate between 30–50°C per minute irrespective of tumour size, and that the tissue must be thawed as quickly as possible once the desired minimum temperature has been reached. For controlled cryotherapy one has to rely on freezing damage as damage caused during thawing is difficult to predict.Freezing probes of different designs and sizes must be available to meet the demands mentioned for heat exchange and a pressure gauge must be at hand to record the force with which the freezing probe rests against the tissue. Finally a reliable flowmeter must be found with which to measure the number of calories drained away from the tissue.