Imaging with diffusing light: an experimental study of the effect of background optical properties

The overall image quality and diagnostic potential of time-resolved transmittance imaging depend on sensitivity to optical contrast, capacity to discriminate scattering from absorption contributions, and spatial resolution. We have investigated experimentally the effects of the optical properties of the background medium on the overall image quality of optical imaging based on fitting the experimental data to the solution of the diffusion equation and on time gating. Images were acquired from phantoms with different background optical properties, while the optical contrast between inhomogeneities and background is kept constant. Data were collected every 0.2 cm over a 6 cm x 6 cm area from realistic tissue phantoms containing cylindrical inhomogeneities (1 cm high and 1 cm in diameter) embedded in a 5-cm-thick turbid slab. The optical coefficients of the background were varied in the ranges of 5-15 cm(-1) for transport scattering and 0.02-0.08 cm(-1) for absorption. The optical contrast for the inclusions was kept at values of -50% and +50% for the scattering and -75% and +300% for the absorption. The results show that both high scattering and high absorption are beneficial. (C) 1998 Optical Society of America.