Capacitive charge approach to diffuse optical tomography systems

Abstract

In this study the capacitive charge model approach has been explored to evaluate depth information of continuous wave (CW) diffuse optical tomography (DOT) systems. CW DOT systems have two geometric data acquisition structures depending on the laser source and photo-detector placements on the device surfaces. These geometries are transmission through and back reflection types. Most of the scanning geometries do not allow transmission through measurements. Hence, researchers had been trying to make more reliable back reflected CW DOT imaging systems for almost 30 years. Some researchers and companies had been using the mixture of transmission through and back reflection geometry models which is also equivalent to ring model. Ring model has been normally used for breast and newborn head imaging. The exponentially decaying nature of light gives less information about depth of scanning view for back reflected DOT devices. Diffusing light loses its energy along the depth profile. Back reflected escaping diffuse light involves less information about deeper voxels of interesting tissue or tissue like phantoms. On the other hand transmission through geometry uses only one depth surface thus giving more accurate information. In this work back reflected DOT geometry has been mimicked as a capacitor. Instead of electron accumulation versus time we used photon accumulation versus depth. The forward model transport matrix was built according to the time independent diffusion equation. One source and five different detector position’s experimental measurement data were acquired by multifiber spectrometers and simultenously acquired from homogenous and heterogenous multilayered, solid, sylindirical, silicon phantoms. Five different distance, heterogenous multilayer, detector's data have been divided over five homogenous detector's data to generate perturbation data. Perturbation data and the forward model weight matrix have been used to recover heterogenous, absorption differences from the homogenous medium and then two dimensional image has been constructed.