| dc.description.abstract | This study focuses on developing three-dimensional image reconstruction algorithm of near-infrared diffuse optical tomography (NIR DOT) system for detecting breast cancer. The image reconstruction algorithm of DOT is based on the diffusion equation, and involves both the forward calculation and inverse reconstruction. The forward calculation solves the diffusion equation by using the finite element method (FEM) for calculating the distribution of transmitted light under the condition of presumed light source and optical coefficient (absorption and scattering coefficients) of the model. The inverse calculation reconstructs the distribution of the optical coefficient by using Newton′s method to minimize the difference between theory and measured data. Due to ill-posed nature of the inverse problem, Tikhonov regularization is utilized to stabilize the reconstruction result. For verification of developed reconstruction algorithm, different designated simulation cases, including different optical coefficients, size, and location of tumor, were used. The reconstruction results then were assessed by a set of resolution measures that compare reconstructed image with target one, and provide the quantitatively evaluation for the reconstructed image quality. Moreover, reconstruction images were also quantitatively evaluated by using mean square error (MSE). The evaluation results shows that, under condition of using 80-mm-diamater cylinder phantom, tumor with diameter more than 15 mm, located at the off-center distance 0 mm and contrast of 2, can be reconstructed. However, if the optical contrast of tumor were more than 2.5, it would lead to over-estimation of optical properties. It also shows significant crosstalk issue between absorption and scattering coefficients if the ratio of absorption-contrast to scattering-contrast is more than 1.5. | en_US |