Cryosurgical treatment of epitheliomas using the cone-spray technique

By use of cone-shaped devices to confine liquid nitrogen spray to a restricted area on the skin surface, it is practical to treat selected epitheliomas without the aid of thermocouples. "Depth dose" is estimated by measuring the lateral spread of freezing on the surface beyond the restricted area, timing the duration of freeze, and from this information calculating the depth of freeze and the relationship of various isotherms (such as the --25 degrees C isotherm) with the frozen mass.