Ultrasound-modulated optical tomography for dense turbid media

Continuous-wave ultrasonic modulation of scattered laser light has been used to image objects in tissue-simulating turbid media for the first time. We hypothesized that the ultrasound wave focused into the turbid media modulates the laser light passing through the ultrasonic focal zone. The modulated laser light collected by a photomultiplier tube reflects the local mechanical and optical properties in the focal zone. Buried objects in 5-cm thick tissue phantoms (absorption coefficient µ_a = 0.1 cm^(-1), reduced scattering coefficient µ_s' = 10 cm^(-1)) were located with millimeter resolution by scanning and detecting alterations of the ultrasound-modulated optical signal