Development of a smart holmium:YAG laser lithotriptor.

Background and Objective The purpose of this study was to develop a feedback control system for the pulsed holmium: YAG medical laser that enhances tissue selectivity and safety by discriminating between soft and hard biological tissue such as urinary and biliary calculi and bone. Study Design/Materials and Methods The ability to discriminate is achieved by monitoring prompt laser-induced visible/NIR photoemissions via retrograde transmission over the laser delivery fiber in conjunction with a developed detection algorithm. Results Experimental data are presented for a system that employs this discrimination scheme with an electro-optic shutter for rapid intrapulse feedback control of holmium laser-based lithotripsy procedures. The results demonstrate the feasibility of a lithotriptor that can deliver 1 J per pulse to calculi yet limit errant discharges to surrounding urinary tract tissue to ≲ 0.1 J. Conclusion Based on animal tissue safety data, the laser margin of safety is improved by an order of magnitude. Lasers Surg. Med. 21:20–28, 1997 © 1997 Wiley-Liss, Inc.