In situ local tissue characterization and imaging by backscattering acousto-optic imaging

We use an imaging system taking advantage of a focused ultrasonic field to mark the photon trajectories in a biological sample by modulating the optic al paths in the focal zone. We show the applicability of this setup to vari ous geometrical configurations, such as forward and backward scattering. Th e modulated speckle detected on a CCD camera reflects, after parallel proce ssing, the local optical properties of the tissue in the focal zone. We pro pose to use the backscattering geometry to estimate the local effective att enuation coefficient. Finally we compare images which have been obtained th rough several centimeters of biological tissue, both in forward and in back ward geometry. (C) 2001 Elsevier Science B.V. All rights reserved.