1. Yufeng Zhou and Xiaobin Wilson Gao School of Mechanical & Aerospace Engineering Nanyang Technological University

2. Introduction Ultrasound therapy is an emerging modality in clinics; High-intensity low-duration ultrasound pulse can be implemented in drug delivery, thrombolysis, etc. Histotripsy can be used to erode soft tissue noninvasively; Bubble dynamics plays an important role in such application.

3. Experiment Setup

4. Lesion Growth N = 1 N = 2 N = 5 N = 10 N = 50N = 100 3.3 MHz, 30 ms burst, 1 Hz pulse repetition rate, 150 W N = 20 N = 70

5. Passive Cavitation Detection 1 st pulse 100 th pulse 3.3 MHz, 30 ms burst, 1 Hz pulse repetition rate, 150 W output

6. Effect of Pulse Duration 3.3 MHz, 1 Hz pulse repetition rate, 150 W

7. Lesion Growth 1.1 MHz, 100 ms burst, 1 Hz pulse repetition rate, 150 W N = 1 N = 2 N = 5 N = 10 N = 20 N = 50 N = 70N = 100

8. Effect of Frequency 1.1 MHz, 1 Hz pulse repetition rate, 150 W

9. Ex Vivo Results 3.3 MHz, 1 Hz pulse repetition rate, 150 W

10. Ex Vivo PCD 3.3 MHz, 1 Hz pulse repetition rate, 150 W output

11. B-Mode Sonography 3.3 MHz, 30 ms burst, 1 Hz pulse repetition rate, 150 W output N = 1 N = 5 N = 50 N = 100

12. Conclusions Characteristics of bubble dynamics vary with the progress of the ultrasound therapy; Ultrasound parameters (i.e., burst duration, frequency, target type) have great influence on the bubble dynamics, thermal effects, and consequent lesion formation; Appropriate combination of mechanical and thermal effect would broaden the application; Monitoring bubble dynamics could control the ultrasound therapy effectively and efficiently.