Ultrasonic modulation of diffuse light in turbid media

Continuous-wave ultrasonic modulation of laser light has been used to image objects buried in tissue-simulating turbid media. The ultrasonic wave focused into the turbid media modulated the laser light passing through the ultrasonic field. The modulated laser light collected by a photomultiplier tube reflected primarily the local mechanical and optical properties in the focal zone. Modulated signal was estimated using diffusion theory. The dependence of the ultrasound-modulated optical signal on the off-axis distance of the detector from the optic axis was studied. The mechanisms of ultrasonic modulation of light were discussed