| Summary: | Acousto-optical imaging (AOI) in diffuse media is a hybrid technique that is based on the interaction of multiply scattered laser light with a focused ultrasound beam. A phase-modulated optical field emanates from the interaction region and carries with it information about the local opto-mechanical properties of the insonated media. The goal of AOI is to reveal the optically relevant physiological information while maintaining ultrasonic resolution. Among the state-of-the-art optical detection techniques used for AOI, there is a trade-off between the axial resolution (or ultrasound bandwidth) and the signal-to-noise ratio (SNR). In this paper, a photorefractive-crystal (PRC) based interferometry system is employed to detect acousto-optical (AO) signals in highly diffuse media. This system allows for the use of short pulses of focused ultrasound and is capable of imaging mm-scale inhomogeneities imbedded inside tissue-mimicking phantoms. One-dimensional (1-D) AO image along the transducer axis is obtained from a single, time-averaged time-domain acousto-optical signal, and the axial resolution is determined by the acoustic spatial pulse length, rather than the longer axial dimension of the ultrasonic focal region (as is the case when using a continuous-wave (CW) ultrasound source). Two-dimensional (2-D) images can be constructed by scanning the transducer in one dimension, which results in a reduction in imaging acquisition time and makes fast acousto-optical imaging possible.
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