In Vitro Comparison of Two Electromagnetic Shockwave Generators: Low-Pressure Wide Focus vs High-Pressure Small Focus- Impact on Initial Stone Fragmentation and Final Stone Comminution.

ABSTRACT

Context Recently developed concepts for higher efficacy extracorporeal shockwave lithotripsy with low-pressure wide focus systems resulting in finer fragmentation of the calculi. Objective: To compare two different electromagnetic shockwave sources (low-pressure wide focus [Xinin Lithotripter, XL] vs high-pressure small focus [Siemens Lithoskop, SL]) by sound field measurements and in vitro fragmentation. Evidence Acquisition The CS-2012A XX-ES lithotripter (self-focusing electromagnetic shockwave generator with concave spherical curved electrical coil; XL) was compared to the (SL) (electromagnetic generator with a flat electric coil with an acoustical lens). Different sound field measurements were performed using a fiber-optic hydrophone. Measurements at three different power settings (XL 8.0, 9.3, and 10.3 kV and SL Level 1, 5, and 8). Ten AST stones and 15 BegoStones (9.3 kV, Level 3) with a frequency of 90/minute (SL) and 20/minute (XL). Number of impulses to the first crack and for complete stone comminution (residual fragments <2 mm) was documented. Results: The median number of shockwaves for the first crack in AST stones with the XL was 12 (10-14) and 7 with the SL (6-9). Complete disintegration was accomplished after 815 (782-824) shockwaves with XL and 702 (688-712) with SL. The difference was not statistically significant. The median number of shockwaves to produce the first crack in BegoStones was 524 (504-542) with XL and only 151 (137-161) with SL. Numbers of shockwaves for complete disintegration did not differ significantly (XL 2518 vs SL 2287). Using a wide focus with low pressure shows more homogeneous disintegration. Conclusion: Two stone models showed significant differences regarding form and time of the initial fragmentation. Impulses for stone comminution did not differ significantly. The advantages of a low-pressure wide-focus system include minimal trauma and a homogeneous fragment size but is more time consuming. High-pressure small-focus systems are clinically effective.