CREATION OF A VOLUME LESION IN THE DOG PROSTATE USING NEODYMIUM-YAG LASER COAGULATION - CONCEPTS FOR CLINICAL TREATMENT

Background and Objective: The purpose of this study was to determine t he geometrical development of a coagulated zone in the canine prostate during free beam side fire Nd:YAG laser coagulation. Study Design/Mat erials and Methods: A series of 10 male dogs underwent endoscopic pros tatic Nd:YAG fixed position laser coagulation through a suprapubic cys totomy using a right-angle deflecting delivery catheter (Microvasive, Boston, RIA) at times varying from 10 to 120 seconds at 30 watts. In a ddition, two dogs underwent lasing by pulling the catheter at 1 mm/s i n four quadrants. Acute gross and microscopic pathology specimens were prepared and the lesion shape and volume determined. Results: Analysi s of the coagulated volume showed that during the initial 15 seconds o f lasing, the zone of coagulation approximates a sphere centered on th e urothelium opposite the laser fiber. However, as lasing progressed, the lesion changed from a sphere to an expanding ellipse. This changin g geometry can be explained by the absorption and scatter characterist ics of the laser and the temperature equilibrium that is established w ithin the prostate. Conclusion: An understanding of this time-dependen t geometrical shift from a sphere to an ellipse allows the surgeon to supplement the fixed protocols for lasing at certain positions for giv en amounts of time. Specific plans can then be established for tissue at the bladder neck, apex, anterior stroma, floor, and irregular prost atic regrowth. (C) 1995 Wiley-Liss, Inc.