Efficacy of the Sonolith Vision Lithotripter According to the Electrode Lifespan: An in Vitro Study

Abstract

Electrodes used by the Sonolith Vision lithotripter have a specified lifespan, and the manufacturer recommends replacing the electrode every 35,000 shocks. To evaluate the efficacy of extracorporeal shockwave lithotripsy (SWL) as it relates to electrode lifespan, and establish standard treatment results, we performed an in vitro study. From August to October 2005, 12 sessions of shock testing were performed by a Sonolith Vision lithotripter using four test stones per month. The numbers of consumed electrode shocks (CES) at the beginning of testing were classified as: category 1: 0-9999; category 2: 10,000-19,999; category 3: 20,000-29,999; and category 4: 30,000-35,000 shocks. In each category, the number of test stone broken (TBS) shocks was recorded. The voltage was maintained at 25 kV (100%) for every session. The results were analyzed statistically. TBS scores increased with increasing CES. The mean rates of increase in TBS between categories were 14.7% (category 1 to category 2), 8.4% (category 2 to category 3), and 13.7% (category 3 to category 4). There was a strong positive correlation between CES and TBS scores (r = 0.987; P = 0.01). As the number of consumed electrode shocks increased, the number of test stone broken shocks increased, by an average rate of 12%. Thus when the consumed electrode shocks increase by 10,000 units, the user should increase the number of shocks by about 12% to accomplish equal treatment for all patients.