Focused ultrasound for medical applications

Shadowgraph image of scattered ultrasonic waves (post-processed)

High-intensity focused ultrasound (HIFU) can be used for the ablation of tissue, such as in the case of prostate cancer. However, targeting tissue deeper inside the body remains challenging due to the increased attenuation and scattering of the ultrasonic waves. In this work, the partial and complete obstruction of the ultrasonic beam from a HIFU transducer at bones is investigated. Ultrasonic transmission and reflection under such conditions have scarcely been the focus of previous research. Thus, this work provides a reference based on numerical and experimental results. To this end, numerical simulations are conducted for various bone obstruction configurations as well as a new experimental setup is developed in which focused ultrasonic waves are generated, and temperature and pressure fields at the target area are recorded. In addition, a diffraction-based shadowgraph technique is used for the ultrasound visualization in laboratory experiments. Furthermore, new analysis techniques are developed to process shadowgraph images and to extract quantitative information. Overall, the results of this work provide the basis for future research in the field of therapeutic ultrasound.

IACUC Number: 1819-008a

Christoph Schaal
Associate Professor of Mechanical Engineering