UC Irvine

The main goal of this study was to demonstrate the feasibility of using back-side infrared imaging to estimate the spatial cryogen temperature distribution during a cryogen spurt. Calculations from numerical models showed that the front-side temperature distribution could be identified at the back side of a thin aluminum sheet. Infrared images were obtained at various timepoints during a cryogen spurt from the back side of a 800-μm aluminum sheet and the temperature distribution estimated. The temperature distribution was approximately gaussian in shape. A secondary goal was to calculate the temperature distribution in skin for two cases: 1) uniform cryogen temperature distribution, essentially representative of a 1-D geometry assumption; and 2) nonuniform distribution. At the end of a 100-ms spurt, calculations showed that, for the two cases, large discrepancies in temperatures at the surface and at a 60-μm depth were found at radii greater than 2.5 mm. These results suggest that it is necessary to consider spatial cryogen temperature gradients during cryogen spray cooling of tissue.