| Ultrasound-induced inertial cavitation (IC) has clinical relevance from both diagnostic and therapeutic perspectives. The principle objectives of the studies were to: (1) understand some fundamental aspects of ultrasound contrast agent (UCA) dynamic behaviors, because the presence of UCA provides cavitation nuclei and can increase enhance the cavitation-related bioeffects; (2) investigate the methods of in vivo cavitation detection and quantification in a vascular environment with flow, or during shock wave (SW) treatments, and (3) advance the understanding of how ultrasound-induced cavitation is affected by acoustic parameters, and UCA concentration.; To further understanding of the fundamentals of bubble dynamic models, four shelled bubble dynamics models were compared with variable acoustic driving and shell parameters, and previous experimental bubble dynamics data were analyzed quantitatively based on model simulation.; Previous in vitro studies have shown that ultrasound-induced mechanical bioeffects produced with contrast agents are highly correlated with IC 'dose' (ICD). In this work, both ex vivo and in vivo experiments were conducted to test the hypotheses that: (1) IC activity can be detected and quantified as an ICD using a passive cavitation detection (PCD) system, (2) ICD can be correlated to acoustic parameters and OptisonRTM concentration, and (3) the temporal evolution of IC activity in the in vivo rabbit ear model can be correlated to acoustic parameters.; The cavitation events generated during SW treatments were also investigated based on a B-mode imaging technique. The SW-induced cavitation activity was quantified by measuring the hyperechoic region areas in B-mode images recorded during the SW treatments. The results showed that cavitation activity increased with increasing number of SW pulses. The area of cavitation bubble clouds was enlarged with higher lithotripter charging voltages or fast PRF. The bubble dissolution process detected by B-mode imaging was further simulated based on the calculation of scattering cross-section, while employing bubble dissolution equations and Gaussian bubble size distribution.; The significance of this work is that it provides a better understanding of the mechanisms of ultrasound-induced cavitation, and further refinement of an effective technique for quantifying cavitation activity, which are important for optimizing the protocol of ultrasonic therapies to achieve better therapeutic effects while minimizing undesirable side effects. |
