A study of infrared thermographic assessment of liquid nitrogen cryotherapy.
OBJECTIVE
To assess whether infrared thermography can accurately predict the area of soft tissue necrosis that results from liquid nitrogen cryoprobe therapy.


METHODS
Eight rats received cryosurgery on the shaved abdomen with a liquid nitrogen cryoprobe in a triple-freeze technique. The therapy was monitored with infrared thermography and thermocouple probes. The temperature reached was correlated with the area of tissue necrosis found on histologic examination at sacrifice 1 week after the cryotreatment. A parallel study was carried out on pieces on beefsteak to assess the depth and shape of freeze.


RESULTS
The -20 degrees C isotherm, which is felt to correspond to the cell lethal zone, occupied the inner 70% of the area of the iceball produced. Histologically, 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 cannot be readily used in the oral cavity. However, this study does show that one can clinically estimate that the inner 70% of the area of an iceball produced by liquid nitrogen on soft tissues will ultimately undergo necrosis.
Pogrel
M A
MA
Department of Oral and Maxillofacial Surgery, University of California, San Francisco, USA.
Yen
C K
CK
Taylor
R
R
D000818:Animals; D016923:Cell Death; D003452:Cryosurgery / Q000379:methods*; D007259:Infrared Rays; D009584:Nitrogen / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013817:Thermography / Q000379:methods*
D009584:Nitrogen