Prelimnary Investigations On Reflection-Mode Time-Domian Fluorescence Molecular Tomography-Simulations And Phantom Experiments

Fluorescence Molecular Tomography (FMT) is an emerging imaging modality, which employs the fluorescent probes to locate and characterize in vivo specific cellular molecules and their biochemical environment through spatially revolving the fluorescent properties of tissue. The main objective of this paper is to develop a reflection-mode time-domain fluorescence diffuse optical tomography technique for molecular imaging, on the basis of the General Pulse Spectrum Technique (GPST).Monte Carlo (MC) simulation is a statistical method widely used in physics to deal with the particle-transport issue. For its unique flexibility, MC method has become a powerful tool of modeling light propagation in tissue. A hybrid implementation of two kinds of MC techniques, named Analog MC (AMC) and Variance Reduction MC (VRMC), are developed to simulate fluorescence propagation in heterogeneous tissue, with some strategies used to reduce computational time.The diffusion equation (DE) is the P1 approximation of a more physically-rigorous light propagation model in tissue, the Radiative Transfer Equation, and has been proved to be adequately accurate in case of thick tissue and mathematically tractable, therefore employed as the light-propagation model in the image reconstruction process. The fluorescent light detection relies on a coupled DE that associates the excitation-light with the emission-one. A GPST-formulation of the inverse problem is derived based on normalized Born Ratio to attain a simultaneous recover of fluorescent yield and lifetime with two transform-factors. To avoid the difficulties of the direct solution to the ill-posed linear equation set, the row-fashioned algebra reconstruction technique (ART) is adopted as a regularized method.Numerical simulations and preliminary phantom experiments for the three-dimensional models validate the feasibility and reliability of the proposed algorithm, with the spatial resolution, noise-robustness and so on evaluated. The results demonstrate that the proposed methodology is suitable for further application into FMT. Nevertheless, a lot of improvements on both the instrumentation and methodology are necessarily required prior to clinical applications.