Excimer, Ho:YAG, and Q-switched Ho:YAG ablation of aorta: a comparison of temperatures and tissue damage in vitro.

The adjacent thermal and mechanical tissue damage after normal-mode Ho:YAG (pulse length = 250 mus, lambda = 2.09 mum), Q-switched Ho:YAG (pulse length = 200 ns, lambda= 2.09 mum), and excimer (pulse length = 120 ns, lambda = 308 nm) pulsed laser irradiation of human thoracic aorta samples was studied in vitro. Surface temperatures were monitored during laser irradiation with an IR camera in air or a thermocouple in saline. Histological analysis of the irradiated sites was performed to assess thermal and mechanical damage to tissue surrounding the crater. The ablation of aortic tissue with any of the lasers resulted in a temperature buildup inside the tissue; this effect was most significant for the IR wavelength. Mechanical damage was observed in all cases but was most pronounced for the Q-switched Ho:YAG laser. Excimer ablation in air left behind a smooth surface; however, under saline the result was a much rougher surface.