A three-dimensional transient computational study of 532-nm laser thermal ablation in a geometrical model representing prostate tissue

Objective: Laser with 532-nm wavelength (GreenLight^TM) is clinically approved to treat benign prostatic hyperplasia (BPH). However, low rate of tissue ablation and excessive thermal coagulation are shortcomings of this therapy. The goal of this study was to use a mathematical model to identify clinically viable laser settings that have the potential to improve treatment time and outcomes. Methods: A three-dimensional transient computational model was developed, validated against analytical and experimental results, and utilized to investigate the response of tissues subjected to continuous-wave and pulsed lasers emitting 532-nm light (GreenLight^TM laser). The impact of laser power (10–125 W), pulse duration (100 ns and 100 µs) and pulse frequency (10 and 100 Hz) on tissue ablation and coagulation rates and sizes was explored. Results: Good agreement between the computational model and analytical and experimental results was found. Continuous-wave laser results in 13% less coagulation zone thickness and 10% higher ablation rate than the low frequency pulsed laser. With increasing laser power; ablation rate is expected to increase linearly, while coagulation zone thickness is expected to increase asymptotically. Pulse frequency influence on tissue ablation and coagulation is relevant at high power, but pulse duration is found to have minimal effect at all powers. Conclusions: Laser thermal tissue ablation employing continuous wave mode lasers outperforms that employing pulsed mode lasers. Laser power settings should be carefully selected to maximize the rate of tissue ablation and minimize tissue coagulation.