1D-4 High Speed Imaging of Bubble Clouds in Pulsed Cavitational Ultrasound Therapy - Histotripsy

Our investigations have shown that short (les50 musec) high intensity, low duty cycle ultrasound pulses can achieve significant breakdown of tissue structure at a tissue-fluid interface and in bulk soft tissue. We call this technique "histotripsy", and inertial cavitation is its hypothesized mechanism. To understand the physical basis of histotripsy, a high speed camera was used to image hypothesized bubble clouds generated by ultrasound pulses. The results show the following: (1) Ultrasound pulses generated a bubble cloud both at a tissue-water interface and inside a gel used to mimic the bulk soft tissue. This bubble cloud plays an important role in the histotripsy process; (2) An ultrasound pulse of several musec long can generate a bubble cloud lasting for several hundreds of musec; and (3) the intensity threshold to initiate a bubble cloud is lower at a gel-water interface than inside a gel