Reconstruction Algorithm And Experiment Investigation For Steady-State Fluorescence Molecular Tomography

Fluorescent protein has become a very important tool for the research of protein interaction, and it has very important contribution to life science. However, the existing imaging technology for observation of fluorescent protein is still restrained in the depth of hundreds microns, which means that it can only observe the biological processes in superficial tissue. in order to observe the biological processes in organs or even whole body, steady-state fluorescence molecular tomography (FMT) has been proposed. The multiple scattering of photons in tissue determine that the relationship is nonlinear and the reconstruction problem is an ill-posed problem. Therefore, steady-state FMT reconstruction theory is a very challenging research problem.The main task of this paper is to propose an accurate and fast reconstruction algorithm for steady-state FMT. Therefore we start our work from three different but related theory in FMT.First we propose a FMT reconstruction method based on diffusion approximation with finite element method(FEM), and a direct method is proposed to calculate the Jacobian matrix, which can be more accurate than the traditional adjoint method. Phantom experiments are carried out to demonstrate the validity of our method in both forward problem and inverse problem. These experiments also prove that the direct method reveal more accurate distribution of fluorophore in depth direction.Then we propose a FMT reconstruction method based on Monte Carlo(MC) method accelerated by GPU cluster. With the help of GPU cluster, the bottleneck of the MC calculation which means the large time-consumption of MC is removed. Phantom experiment demonstrates the accuracy of our method not only in high-scattering tissue but also in the low-scattering tissue, however the FMT reconstruction based on diffusion approximation with FEM can only be accurate in high-scattering tissue, meanwhile our method requires only 10 minutes to finish the whole process which is equal to the time-consumption of traditional method based on diffusion approximation. At last the in vivo small animal experiment has demonstrated the application value of this method.At last, a reconstruction method which is suitable for the dual-modality FMT/Micro-CT system is proposed. We induct the structure information of Micro-CT into the FMT reconstruction to reduce the ill-posed of reconstruction algorithm. This reconstruction method includes a Micro-CT guided non-equal voxel MC (NVMC) method and a modified Laplacian regularization method. Simulation and phantom experiment prove that this method can not only increase the calculation accurate in the irregular boundary, but also reduce the time-consumption and occupancy of memory; Experiments also demonstrate that modified Laplacian regularization method can be more accurate than traditional Laplacian method when the non-equal structure information is inducted into the reconstruction. At last the in vivo small animal experiment proves that our method is suitable for the small animal which has irregular boundary and complex distribution of optical coefficients.