Acoustic measurements during holmium:YAG laser ablation of cadaveric human temporal bone: preliminary observations

Abstract

Pulsed IR and UV lasers have been suggested for use in middle ear surgery due to decreased thermal trauma, precise ablation characteristics, and potential fiberoptic delivery. While there has been much focus on the thermal and photoacoustic events that occur during pulsed laser ablation of hard tissue, there are few studies that look at the acoustic energy generated from these devices from an audiologic standpoint. In this study, the mastoid cavities of cadaveric human temporal bones were irradiated with a Ho:YAG laser (lambda equals 2.12 micrometer) with the following parameters: 5, 10, and 15 Hz pulse repetition rate and 1, 2, 4, 6, 8, and 10 W average power. During ablation, acoustic measurements were made using a sound level meter held 5 cm away from the target site. With each set of laser parameters, the sound intensity (dB SPL) exceeded 85 dB. Peak intensity measurements of 125 dB were measured, and a saturation effect was noted above 4 W or 500 mJ/pulse. The clinical significance of these findings is discussed and the acoustical aspects of middle ear function and noise trauma are reviewed.