Dual-frequency setting for urinary stone fragmentation during shock wave lithotripsy: an in vitro study.

Abstract

Extracorporeal shock wave lithotripsy (SWL) is less invasive compared to the other invasive modalities of stone treatment that are gaining popularity. Hence, methods to improve the efficacy of SWL are desirable. We studied the effectiveness of dual frequency on the efficacy of stone fragmentation, but minimizing treatment time. A phantom 10mm spherical BegoStone was fragmented in vitro in a kidney model using an electromagnetic lithotripter (Storz MODULITH®SLX-F2). A total of 78 stones were fragmented each with 3000 shocks at 60Hz or 120Hz or a dual frequency (DF) of 60-120Hz. For the DF setting, the first 1000 shocks were delivered at 60Hz and the next 2000 at 120Hz. Total weight and number of significant fragments of > 3mm (TWSF and TNSF, respectively) and also > 2mm was measured. Results: The mean TWSF was 0.1, 0.16, and 0.08g for 60Hz, 120Hz, and DF 60-120Hz, respectively. The TWSF of DF 60-120Hz was significantly lower than that of 120Hz (p = 0.02), but same as the 60Hz (p = 0.32). The mean TNSF of > 3mm was 2.6, 3.0, and 2.0 for 60Hz, 120Hz, and DF 60-120Hz, respectively, without significant differences between each setting. However, increasing trend of TWSF, TW2mm and TN2mm was seen in the order of DF, 60Hz and 120Hz (p = 0.019, p = 0.004 and 0.017, respectively). Treatment time for 60Hz, 120Hz, and DF 60-120Hz was 50, 25, and 34min, respectively. Dual-frequency setting produced effective stone fragmentation compared to the recommended 60Hz, while decreasing treatment time. DF variation is one other factor that may be tailored for effective stone comminution and needs clinical evaluation.