Hit/Miss monitoring of ESWL by spectral Doppler ultrasound.

The objective of this study was to investigate spectral Doppler ultrasound (US) for monitoring extracorporeal shock-wave lithotripsy (ESWL). In vitro experiments with model stones showed that Doppler spectra acquired after a shock wave hit result in a high peak followed by a decaying signal. The duration of decay was dependent on shock-wave energy, stone size, gas content of the water and the level of disintegration. It typically ranged from 30 ms to 150 ms. It was found, by comparison with optical high-speed imaging and US B-scan imaging, that the signal originated from fragments released by the stone and cavitation. If the monitored volume contained no target, the signal duration was significantly shorter. By this means, hits were reliably distinguished from misses. The results of clinical treatments were highly consistent with those of in vitro experiments. Therefore, spectral Doppler US is an excellent tool for hit/miss monitoring in ESWL.