A STUDY OF INFRARED THERMOGRAPHIC ASSESSMENT OF LIQUID-NITROGEN CRYOTHERAPY

Objective. To assess whether infrared thermography can accurately pred ict the area of soft tissue necrosis that results from liquid nitrogen cryoprobe therapy. Study design. Eight rats received cryosurgery on t he shaved abdomen with a liquid nitrogen cryoprobe in a triple-freeze technique. The therapy was monitored with infrared thermography and th ermocouple probes. The temperature reached was correlated with the are a of tissue necrosis found on histologic examination at sacrifice 1 we ek after the cryotreatment. A parallel study was carried out on pieces of beefsteak to assess the depth and shape of freeze. Results. The -2 0 degrees C isotherm, which is felt to correspond to the cell lethal z one, occupied the inner 70% of the area of the iceball produced. Histo logically, the -20 degrees C isotherm corresponded well to the area of tissue necrosis. In depth, the iceball takes on a semicircular shape. Conclusions. infrared tomography is expensive to use clinically and c annot be readily used in the oral cavity. However, this study does sho w that one can clinically estimate that the inner 70% of the area of a n iceball produced by liquid nitrogen on soft tissues will ultimately undergo necrosis.