| he increasingly widespread use of ultrasound in medicine both for diagnosis and for therapy requires the understanding of the consequences of the passage of ultrasound in the context of human body. In particular, concern for potential bioeffects at the cellular level due to the high local pressure and high local temperature associated with inertial cavitation has prompted interest in this field.;Acoustic inertial cavitation is the rapid growth and violent collapse of gas- and vapor-filled cavities as the consequence of the application of ultrasound in the exposed media, such as the application of the short-pulsed diagnostic ultrasound in tissue. In vitro measurements are presented in order to elucidate the fundamental physical aspects of cavitation threshold determination in controlled media and to establish a "data bank" for the cavitation characteristics in biological materials. Results of in vivo cavitation detection provide the first direct evidence of cavitation inception in a mammal from diagnostic ultrasound.;An experimental apparatus has been developed to measure the thresholds for cavitation induced by pulsed ultrasound in a controlled environment. Focused transducers of center frequency 2.46 MHz and 4.3 MHz were used in the experiments. A clinical diagnostic ultrasound system was also used to produce 4 MHz pulsed ultrasound. Cavitation was detected by an active cavitation detection technique which is sensitive to the strength of the backscattered ultrasound from cavitation bubbles as well as the Doppler-shifted frequency of the backscattered signal. Measurements of inertial cavitation thresholds in aqueous media of different concentrations of nucleation particles, fluids of different viscosities, human blood and dilutions, and calf liver are presented. Polystyrene spheres of diameter 0.1... |
