Quantitative Evaluation of High Power Effect on 532 nm Laser Vaporization of Bovine Prostate In Vitro

Abstract

We investigated the effect of 120 to 200 W high power levels on in vitro vaporization of bovine prostate using a custom-made 532 nm lithium triborate laser system. Light (532 nm) delivered through a newly designed 750 microm core diameter side firing prototype fiber vaporized 114 bovine prostate tissue specimens in saline at 20C using a 2-dimensional scanning system. Various conditions were tested, including 120 to 200 W power, 1 to 5 mm working distance and 2 to 8 mm per second treatment speed. Regardless of treatment speed 180 W was the optimal power to maximize tissue vaporization efficiency by removing 80% more tissue than at 120 W. At 120 and 180 W laser light vaporized tissue more efficiently at a 4 mm per second treatment speed and vaporized equally efficiently at up to 3 mm working distance. At the slowest treatment speed the mean thickness of the coagulation zone at 180 W was 20% thicker than at 120 W (1.31 vs 1.09 mm) but still thin, comparable to previous findings of 1 to 2 mm. In vitro the 532 nm lithium triborate laser showed that 180 W is the optimal power to maximize tissue vaporization efficiency with enhanced coagulation characteristics. These desirable outcomes must be validated in vivo.