Subsurface tissue lesions created using an Nd:YAG laser and cryogen cooling

BACKGROUND AND PURPOSE: Cooling methods are commonly used in dermatology to protect the skin surface during cosmetic laser procedures. This study investigated deep laser heating of tissue in combination with cryogen cooling of the surface for potential noninvasive targeting of subsurface tissue structures in urology. MATERIALS AND METHODS: Porcine liver and skin were studied because they represent simple and difficult tissue models, respectively, for subsurface lesion production. Gross and histologic methods were used to measure lesion dimensions. RESULTS: Liver lesions measured 4.9 +/- 1.2 mm in diameter, while preserving the tissue surface to a depth of 2.1 +/- 0.4 mm (N = 5). Surface temperatures remained below 40 degrees C, while lesion temperatures ranged from 60 to 70 degrees C. Skin lesions measured 4.1 +/- 0.6 mm, while preserving the skin surface to a depth of 1.2 +/- 0.2 mm (N = 4). CONCLUSION: This technique may prove useful to target subsurface anatomic structures in urology.