The enhanced HIFU-induced thermal effect via magnetic ultrasound contrast agent microbubbles

High intensity focused ultrasound (HIFU) has been regarded as a promising technology for treating cancer and other severe diseases noninvasively. In the present study, dual modality magnetic ultrasound contrast agent microbubbles (MBs) were synthesized by loading the super paramagnetic iron oxide nanoparticles (SPIOs) into the albumin-shelled MBs (referred as SPIO-albumin MBs). Then, both experimental measurements and numerical simulations were performed to evaluate the ability of SPIO-albumin MBs of enhancing HIFU-induced thermal effect. The results indicated that, comparing with regular albumin-shelled MBs, the SPIO-albumin MBs would lead to quicker temperature elevation rate and higher peak temperature. This phenomenon could be explained by the changes in MBs' physical and thermal properties induced by the integration of SPIOs into MB shell materials. In addition, more experimental results demonstrated that the enhancement effect on HIFU-induced temperature elevation could be further strengthened with more SPIOs combined with albumin-shell MBs. These observations suggested that more violent cavitation behaviors might be activated by ultrasound exposures with the presence of SPIOs, which in turn amplified ultrasound-stimulated thermal effect. Based on the present studies, it is reasonable to expect that, with the help of properly designed dual-modality magnetic MBs, the efficiency of HIFU-induced thermal effect could be further improved to achieve better therapeutic outcomes.