DIRECT VIDEO MICROSCOPIC OBSERVATION OF THE DYNAMIC EFFECTS OF MEDICAL ULTRASOUND ON ULTRASOUND CONTRAST MICROSPHERES

RATIONALE AND OBJECTIVES. Ultrasound can cause destruction of microbub ble contrast agents used to enhance medical ultrasound imaging. This s tudy sought to characterize the dynamics of this interaction by direct visual observation of microbubbles during insonification in vitro by a medical ultrasound imaging system. METHODS. Video microscopy was use d to observe air-filled sonicated albumin microspheres adsorbed to a s olid support during insonation. RESULTS. Deflation was not observed at lowest transmit power settings, At higher intensities, gas left the m icroparticle gradually, apparently dissolving into the surrounding med ium. Deflation was slower for higher microsphere surface densities. In termittent ultrasound imaging (0.5 Nz refresh rate) caused slower defl ation than continuous imaging (33 Hz), CONCLUSIONS. Higher concentrati ons of microbubbles, lower ultrasound transmit power settings, and int ermittent imaging each can reduce the rate of destruction of microsphe res resulting from medical ultrasound insonation.