Is it ensure, insure, or assure?
cryosurgery cry·o·sur·ger·y (krī'ō-sûr'jə-rē)
The selective exposure of tissues to extreme cold, often by applying a probe containing liquid nitrogen, to bring about the destruction or elimination of abnormal cells.
therapeutic technique in which localized freezing is used to remove or destroy diseased tissue. Rapid cooling of body tissues to a temperature of -60 C or lower causes ice crystals to form, disrupting cell structure and, ultimately, killing the cell. Freezing may also destroy tissues by triggering an immune response, releasing intracellular proteins that attract natural antibodies. These antibodies, in turn, destroy the diseased cells