Investigation of the Scattering of Focused Ultrasonic Waves at Bones

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. In addition, a diffraction-based shadowgraph technique is used for the ultrasound visualization in laboratory experiments. Imaging of focused ultrasonic waves is performed in water with no obstruction, varying partial obstruction, as well as with complete obstruction by bones phantoms. It is shown that there is reasonable agreement between the findings from experiments and simulations. While the field of view in experiments is limited, the entire pressure field in the area of interest can be investigated in numerical simulations. Overall, the results of this work provide a basis for future research in the field of therapeutic ultrasound.