Effect of ultrasonic intensity and intervals of ultrasonic exposure on efficiency of sonochemiluminescence in gel phantom for sonodynamic therapy

Sonodynamic treatment (SDT) is one of the non-invasive modalities for cancer treatment. In SDT, ultrasound, reactive oxygen species (ROS) generated from cavitation bubbles, and a sonosensitizer are used in combination. In this study, high-intensity focused ultrasound (HIFU) was employed as ultrasound to generate and oscillate cavitation bubbles. When cavitation bubbles oscillate and collapse, the gas inside the bubble is extremely compressed and heated, inducing ROS generation. The disadvantage of SDT is a long treatment time because of its smallness of a treatment region by a shot of HIFU. To overcome this, the effect of the intensity and interval of HIFU for oscillating cavitation bubbles was investigated by using luminol sonochemiluminescence and high-speed imaging. The results showed that a HIFU exposure sequence with an interval of 300 ms and a burst-wave intensity of 0.25 kW cm-2 improve the energy efficiency of ROS generation.