Ultrasound-assisted optical reflectometry in highly scattering media

We have developed an optical reflectometry system to investigate the inside of a scattering medium by using focused ultrasound wave to specify the mea suring point. The reflected light is generated by the variation of the refr active indices induced by a focused ultrasound wave, The optical reflectome try technique enables us to observe an internal structure such as a human t issue noninvasively for biomedical applications. We have observed samples w hich consist of an agarose block with a cubic piece of agarose stained with a dye as an absorptive material, The intensity of the light reflected from the focal region of the ultrasound is decreased when the measuring point w as in the stained agarose section because of absorption by the dye. Further more, we have observed a sample with a weak scattering object made of agaro se surrounded by strong scattering agarose that contains poly(methyl methac rylate) (PMMA) particles.