Nd:YAG laser irradiation in combination with contact tissue cooling for creation of subsurface thermal lesions

This study investigates deep laser coagulation of tissue in combination with contact cooling of the tissue surface for potential use in noninvasive urology procedures. A laser probe was designed, built, and tested for combination Nd:YAG laser irradiation and sapphire contact cooling of liver and skin tissue samples, ex vivo. Gross and histologic examination was used to quantify thermal lesion dimensions. Liver lesions measured 5.5 ± 0.3 mm in diameter, while preserving the tissue surface to a depth of 2.1 ± 0.2 mm (n = 5). Skin lesions measured 4.3 ± 0.9 mm in diameter, while preserving the skin surface to a depth of 1.1 ± 0.2 mm (n = 6). There were no statistical differences in lesion diameter and layer of preserved tissue between contact (sapphire) cooling and prior non-contact (cryogen spray) cooling results for a given tissue type (p > 0.05). Noninvasive laser procedures targeting tissue structures for thermal coagulation within a few millimeters of the tissue surface are feasible and may expand the use of combined laser/cooling techniques for applications in urology. In vivo animal studies are currently in development to optimize the laser and cooling parameters for potential clinical applications.