Quantitation and mapping of tissue optical properties using modulated imaging

We describe the development of a rapid, noncontact imag- ing method, modulated imaging MI, for quantitative, wide-field characterization of optical absorption and scattering properties of tur- bid media. MI utilizes principles of frequency-domain sampling and model-based analysis of the spatial modulation transfer function s-MTF. We present and compare analytic diffusion and probabilistic Monte Carlo models of diffuse reflectance in the spatial frequency domain. Next, we perform MI measurements on tissue-simulating phantoms exhibiting a wide range of l* values 0.5 mm to 3 mm and s /a ratios 8t o 500, reporting an overall accuracy of approxi- mately 6% and 3% in absorption and reduced scattering parameters, respectively. Sampling of only two spatial frequencies, achieved with only three camera images, is found to be sufficient for accurate deter- mination of the optical properties. We then perform MI measurements in an in vivo tissue system, demonstrating spatial mapping of the ab- sorption and scattering optical contrast in a human forearm and dy- namic measurements of a forearm during venous occlusion. Last, met- rics of spatial resolution are assessed through both simulations and measurements of spatially heterogeneous phantoms. © 2009 Society of