Investigation of differences between nanosecond electropulse and electrohydraulic methods of lithotripsy: a comparative in vitro study of efficacy.

PURPOSE To compare the effectiveness of novel nanosecond electropulse lithotripsy with standard electrohydraulic lithotripsy to demonstrate and authenticate their differences because both modalities appear to be similar. MATERIALS AND METHODS An in vitro fragmentation study was conducted using cuboid BegoStone phantoms, which mimic hard and soft stones, based on an established model. Three different stone sizes were used in the testing having volumes of 100, 256, and 320 mm(3). A nanosecond electropulse lithotripter (NEPL) and an electrohydraulic lithotripter (EHL) were operated using a range of probe sizes at comparable energy settings and pulse rates with the objective of obtaining a stone fragment <2 mm. To compare the efficacy of these two lithotripters, the number of pulses needed for stone phantom fragmentation was recorded according to probe size and energy setting, which were then converted into units of cumulative energy. RESULTS The results clearly demonstrated that, for all operating modes and stone phantom types, the NEPL device needs much less cumulative energy and thus fewer pulses and consequently less time to achieve stone fragmentation than the EHL device. The disparity in the results is explained by the dissimilar mechanisms at work in the compared lithotripters during destruction of the stone. The electropulse stone disintegration mechanism transfers energy directly into the stone because of discharge penetration into a solid body. This contrasts with the electrohydraulic mechanism in EHL in which energy is transferred through the liquid medium, which also creates a damaging shockwave. CONCLUSIONS The findings demonstrate that, for all operating modes and stone types, the NEPL device needs much less cumulative energy and thus fewer pulses for stone fragmentation than the EHL device. The disparity in the results is explained by the dissimilar mechanisms at work in the compared lithotripters during destruction of the stone.