Measuring tissue properties and monitoring therapeutic responses using acousto-optic imaging

Acousto-optic imaging is a hybrid imaging technique that exploits the interaction between light and sound to image optical contrast at depth in optically turbid media with the high spatial resolution of ultrasound. Quantitative measurement of optical properties using this technique is confounded by multiple parameters that influence the detected acousto-optic signal. In this article, we describe the origin of the acousto-optic response and review techniques that have been proposed to relate this response to the optical properties of turbid media. We present an overview of two acousto-optic sensing approaches. In the first, we demonstrate that the local transport mean free path within turbid media can be obtained by varying the pressure of the ultrasound field and processing the resulting acousto-optic signals. In the second, we demonstrate that the acousto-optic response elicited by a high-intensity ultrasound field during thermal therapy can be used to monitor the onset of lesion formation, ascertain lesion volume, and provide real-time control of exposure duration.