Temporal and spectral characteristics of the impulsive waves produced by a clinical ballistic shock wave therapy device

Abstract

This study characterizes the temporal and spectral property of the mechanical impulsive waves produced by a clinical ballistic shock wave therapy device. The impulsive waves were generated by a projectile impacting a metallic shock wave transmitter, and were measured using a laser vibrometer that detects vibrations on the front surface of the shock wave transmitter. The shock wave transmitter considered in the measurement has a circular flat surface tip with a diameter of 15 mm. The results showed that the measured impulsive wave was resonated at 93.4 kHz and modulated with a relatively low frequency of 3.7 kHz to form a heavily damped pulse wave lasting for longer than 2 ms. Multiple impulsive waves produced at high output settings, were observed for the first time, and their clinical implication needs to be elucidated in the future study. Despite measurements made on the cavitation free air born impulsive waves, the study was justified by the experimental clarification that their temporal and spectral properties were characteristically similar to those of the impulsive waves produced in water, more representative to clinical conditions. The present results are expected to deliver critical information for assessing the shock wave dose delivered from a clinical radial extracorporeal shock wave device to patients.