Acoustic characterization and assessment of renal injury with a broad focal width electrohydraulic lithotripter

Abstract

This study provides an independent assessment of a novel lithotripter (LG-380, Tissue Regeneration Technologies), marketed as having a long-life self-adjusting spark gap electrode and producing a low-pressure, broad-focal-zone acoustic field. For acoustic characterization we coupled the therapy head of the lithotripter to a water tank and mapped the field using a fiber-optic hydrophone (FOPH-500, RP Acoustics). At the target point of the lithotripter, the peak positive pressure (P +) remained relatively stable (~19±5 MPa at power level 9) during the 6000 shock waves (SWs) lifetime of the electrode. The position of maximum P + (~35 MPa at PL9) was 35mm distal to target point and shifted progressively toward the therapy head as the electrode aged, reaching the target point (while reducing to P + ~20 MPa) after ~5000 SWs. This was likely due to a slight movement in position of the self-adjusting spark gap—changing the focus of the shock wave and the dimensions of the focal volume of the lithotripter. Kidney injury was assessed using an established pig model by routine measures of renal function and quantitation of lesion size. Simulated clinical treatments (3000 SWs dose) damaged <0.1% functional renal volume, suggesting minimal potential for adverse effects with low-pressure broad-focal-zone lithotripters. [NIH DK43881.]