Adaptive Ultrasound Focusing Through the Cranial Bone for Non-invasive Treatment of Brain Disorders.

Focused ultrasound holds great promise in therapy for its ability to target non-invasively deep seated tissues with non-ionizing therapeutic beams. Nevertheless, brain applications have been hampered for decades by the presence of the skull. The skull indeed strongly reflects, refracts and absorbs ultrasound, which defocuses the therapeutic ultrasound beams. In this chapter, we will first show how the structure of the skull impacts the ultrasound beams and how it narrows the frequency range that can be envisioned for transcranial therapy. We will then introduce different methods that have been developed and optimized to compensate the defocusing effect of the bone. Finally, we will provide an overview of past, current and future treatments of brain disorders.