A method for phase aberration correction of high intensity focused ultrasound fields using acoustic nonlinearity

Abstract

High intensity focused ultrasound (HIFU) therapies are often affected by aberrations induced by soft tissue heterogeneities. To mitigate these aberrations, phase corrections at different elements of a HIFU transducer array can be introduced, if suitable feedback is available. Existing feedback approaches include maximization of focal tissue displacement induced by acoustic radiation force or scattering from a cavitation bubble nucleated at the focus. Here we propose an aberration correction method based on backscattering of strongly nonlinear HIFU waves that are present only at the focus. A 1.5 MHz, 12-element sector array was integrated with a coaxially aligned imaging probe (P7-4). Each element of the array emitted a short, high-amplitude pulse through the aberrative layer toward the focus in tissue, and the imaging probe recorded the backscattered signal at higher frequencies. The focusing gain of each sector element was sufficient to generate a highly nonlinear focal waveform, which allowed localizing...