ENHANCEMENT OF SONODYNAMIC TISSUE-DAMAGE PRODUCTION BY 2ND-HARMONIC SUPERIMPOSITION - THEORETICAL-ANALYSIS OF ITS MECHANISM

Among the nonthermal effects of ultrasound, acoustic cavitation may ha ve the highest potential for therapeutic applications if it can be som ehow controlled. Recent in vitro and in vivo experiments have demonstr ated that sonochemically active cavitation can be enhanced an order of magnitude by superimposing the second harmonic onto the fundamental i n insonation, Moreover, they have shown that sonochemically active cav itation can be controlled with relative ease, thereby even in a progre ssive wave field, The effect of second-harmonic superimposition on the rectified diffusion through the gas-liquid interface of cavitated mic robubbles is estimated theoretically, The theoretical rectified diffus ion rate explained an asymmetric behavior of the threshold for produci ng sonodynamic tissue damage as a function of the fundamental and the second-harmonic amplitudes, The tissue damage was produced with a focu sed progressive wave in a liver lobe of a mouse administered with a so nodynamically active agent, The result suggests that the acceleration of the rectified diffusion is a primary mechanism of the enhancement o f sonodynamically effective cavitation by second-harmonic superimposit ion.