Growth and collapse of vapour bubble and shockwave emission around holmium laser beam: theory and experiments

Abstract Holmium laser therapy is used in many urological applications in humans. Most important among these are ablation of prostate tissue in benign prostatic hyperplasia and stone resection in the urinary system (lithotripsy). During treatment, short pulses of high intensity laser are transmitted through a liquid (blood or urine) medium. Heating of the liquid by the laser beam was found to generate vapour bubbles; the bubbles then go through growth and collapse phases reaching internal pressure of several thousand bar. This leads to formation of a pressure shockwave that propagates outwards. A simulation is presented of growth and collapse of a vapour bubble around a Ho : YAG laser beam. Experimental results for the time evolution of a bubble induced by a holmium laser beam are presented. Results of shockwave pressure measurements are also shown. The experimental results are in fairly good agreement with the simulation.