Effect of scanning the focus on generating cavitation bubbles and reactive oxygen species by using trigger high-intensity focused ultrasound sequence

Abstract

In the sonodynamic treatment, reactive oxygen species (ROS) are generated to damage cancer cells. The efficient generation of ROS, therefore, is significant for the treatment. The trigger high-intensity focused ultrasound (HIFU) sequence, consisting of an extremely high intensity short trigger pulse followed by a medium-intensity and long sustaining burst, was tested for this purpose, with and without scanning the focus, in this study. The distribution of generated cavitation bubbles was observed using a high-speed camera and the amount of generated ROS was quantitatively determined by the KI method. As a result, the trigger HIFU sequence generated several times more ROS than the trigger pulse alone, and the sequence with scanning the focus generated more than twice the amount of ROS than that without scanning the focus when the intermission time between the trigger pulse and the sustaining burst was considered. These suggest that the trigger HIFU sequence with scanning the focus is efficient for generating ROS.

Relation between thresholds of free radical generation and atomization under ultrasound exposure

“…4) In the field of medical application, it has been suggested that atomization has an important role in high-intensity focused ultrasound therapy. [5][6][7] Cavitation is the key mechanism of sonodynamic therapy, [8][9][10][11][12] which combines ultrasound and a sonosensitizer (sonochemical sensitizer).…”

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

“…KI method, employing a KI solution, can evaluate the amount of ROS quantitatively. 25,26) A luminol solution can visualize the region of ROS generation 27) by sonochemiluminescence, which is a luminescent reaction caused by ultrasound. 28,29) In a liquid, however, cavitation bubbles are freely swept away by the acoustic radiation force, which is different from the situation in tissue.…”

Weakly nonlinear theory on ultrasound propagation in liquids containing many microbubbles encapsulated by visco-elastic shell

“…Applications of ultrasound in the medical field have recently received significant attention, and hence, several developments have taken place in this field. [1][2][3][4][5][6][7] The use of microbubbles as ultrasound contrast agents (UCAs) has drastically improved the resolution of images, [8][9][10][11] and ultrasound diagnosis using UCA was first performed in the late 1960s. 12,13) In most UCAs, the gas inside the bubble is stabilized against dissolution by being encapsulated in a lipid shell, membrane, etc.…”