Acoustic pressure amplitude thresholds for rectified diffusion in gaseous microbubbles in biological tissue

摘要: One of the mechanisms often suggested for biological action ultrasonic beams irradiating human tissues is concerned with presence in minute gaseous bubbles which may, under influence field be stimulated to grow a size at resonance or collapse occurs severe associated shear stresses. The evidence existence microbubbles reviewed. results calculations, using two existing theoretical models, peak pressure threshold as function frequency are presented. normalized resonant bubble, and presented three bubble radii (1, 2, 3.5 μm) different values gas concentration tissue between 0.1 1. from models differ suggesting that an improved model better experimental data calculations would appropriate further calculations. thresholds calculated range below amplitudes used continuous wave diagnostic instruments, indicating need more careful investigation both this damage mechanism exposures routine diagnosis. typical (transient) exposure conditions pulse‐echo equipment presented, rectified diffusion stable cavitation improbable phenomena these circumstances.