DETECTION OF ACOUSTIC-EMISSION FROM CAVITATION IN TISSUE DURING CLINICAL EXTRACORPOREAL LITHOTRIPSY

A 1-MHz focused hydrophone has been used to search for acoustic emissi on expected to arise from cavitation occurring in tissue during clinic al extracorporeal shock-wave lithotripsy (ESWL), The hydrophone is aco ustically coupled to the patient's skin and the focus directed at dept h in tissue under ultrasound guidance, The measured amplitude-time var iation of the acoustic emission from tissue near the shock-wave focus of the Storz Modulith SL20 lithotripter has been examined in four pati ents, There is evidence of increased amplitude acoustic emission at 1 MHz from regions within tissue that also appear hyperechoic in simulta neously acquired ultrasound images. The acoustic emission from these r egions decays from an initial peak to the noise level in about 500 mu s following each shock-wave pulse, Within this period, a second peak, often of higher amplitude than the first, is typically observed about 100 mu s after the shockwave, The time between the initial and second peaks is found to increase with increasing shock-wave amplitude, The r esults are similar to those previously observed from cavitation induce d by shock-wave exposure in water and indicate that the 1-MHz acoustic emission arises from inertial cavitation in tissue during clinical ES WL. Copyright (C) 1996 World Federation for Ultrasound in Medicine & B iology