Holmium:YAG laser stapedotomy: preliminary evaluation

摘要

Abstract: This study investigated the use of a pulsed Holmium:YAG ($lambda $EQ 2.09 $mu@m) laser-fiber microsurgical system for laser stapedotomy. This system ablates human stapes bones effectively with minimal thermal damage. The study was designed to determine the effectiveness of the Ho:YAG laser (Schwartz Electro Optics, Inc., Orlando, FL) for stapedotomy and to evaluate temperature changes within the cochlea during the ablation process. Human cadaveric temporal bones were obtained and the stapes portion of the ossicular chain was removed. A 200 $mu@m diameter low OH quartz fiber was used to irradiate these stapes bones in an air environment. The laser was pulsed at 2 Hz, 250 $mu@sec pulse width and an irradiance range of 100 - 240 J/cm$+2$/ was used to ablate holes in the stapes footplate. The resultant stapedotomies created had smooth 300 $mu@m diameter holes with a minimum of circumferential charring. Animal studies in-vivo were carried out in chinchillas to determine the caloric spread within the cochlea. A 0.075 mm Type T thermocouple was placed in the round window. Average temperature change during irradiation of the stapes footplate recorded in the round window was 3.6$DGR@C. The data suggest that stapedotomy using the Ho:YAG laser can result in a controlled ablation of the stapes footplate with minimal thermal damage to the surrounding stapes. Optical coupling using fiberoptic silica fibers is an ideal method for delivering laser energy to the stapes during stapedotomy. !20