Rapid quantitative imaging of high intensity ultrasonic pressure fields

Abstract

High-intensity focused ultrasound (FUS) is a noninvasive technique for thermal or mechanical treatment of tissues that can lie deep within the body, with a growing body of FDA-approved indications. There is a pressing need for methods to rapidly and quantitatively map FUS beams for quality assurance in the clinic, and to accelerate research and development of new FUS systems and techniques. However, conventional ultrasound pressure beam mapping instruments including hydrophones and optical techniques are slow, not portable, and expensive, and most cannot map beams at actual therapeutic pressure levels. Here, we report a rapid projection imaging method to quantitatively map FUS pressure beams based on continuous-wave background-oriented schlieren (CW-BOS) imaging. The method requires only a water tank, a background pattern and a camera, and uses a multi-layer deep neural network to reconstruct beam maps. Results at two FUS frequencies show that CW-BOS imaging can produce high-resolution quantitative projected FUS pressure maps in under ten seconds, that the technique is linear and robust to beam rotations and translations, and that it can accurately map aberrated beams.