Imaging of optical scattering contrast using ultrasound-modulated optical tomography

Using a CCD-based speckle contrast detection scheme of ultrasound-modulated optical tomography (UOT), we show the feasibility of imaging objects having different optical scattering coefficients relative to the surrounding scattering medium. Our results show that the spatial resolution depends on the ultrasound parameters and the image contrast depends on the difference in scattering coefficient between the object and the surrounding medium. Experimental measurements are in agreement with Monte Carlo simulations and analytical calculations. This study complements previous UOT experiments that demonstrated optical absorption contrast. It also demonstrates that UOT complements photoacoustic tomography, which is sensitive to optical absorption contrast.