A new acoustic lens design for electromagnetic shock wave lithotripters.

Abstract

The third‐generation electromagnetic (EM) shock wave lithotripters often have narrow focal width and high‐peak pressure compared to the original HM‐3. In addition, the pressure waveform produced by a typical EM lithotripter has a secondary compressive wave that suppresses lithotripter pulse induced cavitation, which is an important mechanism for stone comminution. These features have been contributed to the reduced effectiveness of the modern EM lithotripters. To overcome these drawbacks, we have designed a new acoustic lens for the Siemens Modularis EM lithotripter that produces an idealized pressure waveform similar to the HM‐3 with broad focal width and low‐peak pressure. At acoustic pulse energy of 53 mJ, the new lens design enlarges the −6 dB focal width of the Modularis by 47% while significantly reducing the second compressive wave throughout its focal plane. After 2000 shocks, in vitro comminution produced by the original and new lens designs are 100% and 99% at the lithotripter focus, and (49.7±15.0)% and (75.3±8.74)% (p < 0.001) at 10 mm off axis, respectively. Corresponding values in vivo are (63.4±17.4)% and (83.3±8.5)% (p < 0.01), demonstrating the significant performance improvement provided by the new lens design. [Work supported by NIH Grant Nos. R01DK052985 and S10RR016802.]