Study on ultrasound sequence with scanning the focus to generate reactive oxygen species efficiently for sonodynamic therapy

Abstract

In the process of sonodynamic treatment, reactive oxygen species (ROS) are generated to damage cancer cells, and therefore the reproducible efficiency of ROS generation is significant for the treatment. Our previous study demonstrated that trigger HIFU (High-intensity focused ultrasound) exposure sequence, consisting of a high-intensity short trigger pulse and a medium-intensity long sustaining burst, was effective for enhancing the efficiency of ROS generation. To generate ROS more efficiently, trigger HIFU sequences with focus scanning were tested in this study. Considering the diffusion of the precursors of ROS, the optimum time of scanning the focus was studied. A KI method and high-speed camera were used to measure the amount of ROS and confirm the distribution of cavitation bubbles in the aqueous solution. The high-speed camera observation confirmed that cavitation bubbles were generated around each focal point similarly in all sequences. The scanning sequence with less intermission time between the high-intensity pulse and low-intensity burst exposures could generate more ROS than the other sequences. This may explain the difference in ROS production. A scanning exposure sequence with the high-intensity pulse immediately followed by the low-intensity burst should improve the ROS production rate.