Acousto‐optic sensitivity mapping of biological tissues under insonification by high‐intensity focused ultrasound.

Abstract

By means of the acousto‐optic effect, a focused acoustic field may perturb the optical paths within a particular region of a highly scattering medium. These perturbations cause the modulation of a speckle pattern formed when multiple optical paths from a coherent source interfere at a detector position. Through analysis of this modulation, the contrast of biological tissues at near‐infrared wavelengths can be exploited to determine the optical properties of biological tissue with a spatial resolution comparable to the dimension of the acoustic focus. It has been demonstrated ex vivo that this technique is capable of monitoring changes in the optical properties of biological tissue in the acoustic focus region during treatments using high‐intensity focused ultrasound. The sensitivity of this approach to the optical properties of regions external to the focus has not yet been examined; this is a key question in determining the clinical viability of this approach. This work presents modulation depth sensitiv...