IMAGING WITH DIFFUSING LIGHT - AN EXPERIMENTAL-STUDY OF THE EFFECT OFBACKGROUND OPTICAL-PROPERTIES

The overall image quality and diagnostic potential of time-resolved tr ansmittance imaging depend on sensitivity to optical contrast, capacit y to discriminate scattering from absorption contributions, and spatia l resolution. We have investigated experimentally the effects of the o ptical properties of the background medium on the overall image qualit y of optical imaging based on fitting the experimental data to the sol ution of the diffusion equation and on time gating. Images were acquir ed from phantoms with different background optical properties, while t he optical contrast between inhomogeneities and background is kept con stant. Data were collected every 0.2 cm over a 6 cm x 6 cm area from r ealistic tissue phantoms containing cylindrical inhomogeneities (1 cm high and 1 cm in diameter) embedded in a 5-cm-thick turbid slab. The o ptical coefficients of the background were varied in the ranges of 5-1 5 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% an d +50% for the scattering and -75% and +300% for the absorption. The r esults show that both high scattering and high absorption are benefici al. (C) 1998 Optical Society of America.