SPATIALLY SELECTIVE PHOTOCOAGULATION OF BIOLOGICAL TISSUES - FEASIBILITY STUDY UTILIZING CRYOGEN SPRAY COOLING

Successful laser treatment of selected dermatoses such as hemangiomas requires thermally induced damage to blood vessels while protecting th e epidermis. We present and test a procedure in a rabbit liver tissue model that utilizes cryogen spray cooling during continuous Nd:YAG las er irradiation to induce deep photocoagulation necrosis while protecti ng superficial tissues from thermal injury. Gross and histologic obser vations are consistent with calculated thicknesses of protected and ph otocoagulated tissues and demonstrate the feasibility of inducing spat ially selective photocoagulation when cryogen spray cooling is used in conjunction with laser irradiation. This procedure may be useful in t he thermal treatment of some pathological conditions for which it is d esired that deep photocoagulation be induced while protecting superfic ial tissues. (C) 1996 Optical Society of America