COMPARISON BETWEEN THE EFFECTS OF CAVITATION INDUCED BY 2 DIFFERENT PRESSURE-TIME SHOCK WAVE-FORM PULSES

Acoustic cavitation generates very large localized pressures and tempe ratures, and thus provides a mechanism whereby physical and biological effects are produced in a high-intensity acoustic field. In this work , we studied the influence of the temporal form of a pressure pulse wa veform on the destructive effects of transient cavitation. Two differe nt shock pressure-time waveforms with nearly the same acoustic energy content were used. The first pressure waveform starts with a tensile w ave followed by a compressive one, and the second pressure waveform st arts with a compressive wave followed by a tensile one. These two pres sure waveforms are called direct and inverse-mode pulses respectively. Based on the measurements presented in this work, we can state that, between the two types of shock pressure pulses studied, the direct-mod e pulse amplifies systematically the cavitation effect. This conclusio n was achieved from a series of several quantitative and qualitative e xperiments: cavitation bubble collapse time, disintegration efficacy o f plaster balls (a kidney stone-mimicking material), macroscopic study of lesions in agar gel and in vitro isolated rabbit liver tissue dest ruction. Considering these results and those obtained by other researc h groups, we can express that the temporal form of a shock pressure pu lse has a major role on the cavitation effects.