Dosimetry studies utilizing the Urolase right angle firing neodymium:YAG laser fiber.

Neodymium:YAG laser application was performed with the Urolase right angle laser fiber in a potato model and then in vivo in 29 canine prostates in an attempt to define dosimetry and optimal treatment parameters required to maximize tissue ablation and treatment efficacy. Depth and volume of prostatic tissue ablation for single, continuous laser applications with the Urolase fiber were measured at variable power settings from 20 to 60 watts, while holding total energy delivery constant. Peak tissue ablation was observed at 40 watts--up to a maximum of 21 mm tissue penetration in the canine model with a mode of 15 mm. The mean depth of tissue destruction at 40 watts power setting was 15.7 mm, with a mean volume of tissue ablation of 5.5 cc. The mean depth of tissue penetration at 40 watts was more than 30% greater than that observed at 60 watts, and the mean volume of tissue ablation was more than 60% greater than that observed at 60 watts. Holding the power setting constant at 40 watts, the extent of tissue ablation was measured for variable treatment times from 60 to 120 seconds. As treatment time was increased from 60 to 90 seconds, tissue ablation increased significantly. However, beyond 90 seconds of continuous laser application at 40 watts, a plateau in tissue effects was observed, with no real increase in tissue ablation between 90 and 120 seconds. Interruption or discontinuous laser application produced tissue effects which were significantly less than those observed for a single continuous 90 second laser treatment.