FIG. 2.

Acoustic output over electrode lifetime for the TRT LG-380 and Dornier HM3 lithotripters. Each point is the average of 100 shockwaves (SWs). Whiskers indicate standard deviation of the mean. Trace for LG-380 begins after 365 SWs had been fired, while data for HM3 begin with SW#1 and are aligned opposite LG-380 points for convenience. Mean peak positive (P⁺, top) and negative (P⁻, bottom) pressures for the LG-380 (uses a self-adjusting spark-gap electrode) were consistent over 6000 SWs. Mean P⁺ for the HM3 fell ∼25% over 2200 SWs. Recommended lifetime for Dornier-style electrodes is 1000 to 2000 SWs, depending on kV.