| Optical tomography technology has been developing rapidly in recent years. It has made great contribution to the clinical medicine. In optical tomography, low-energy near infrared light is used to probe highly scattering media, and thus to derive qualitative images of the optical properties of these media such as absorption coefficient and scattering coefficient. Optical tomography is expected to be safe, reliable and low cost. As compared to other imaging modalities, optical tomography has the advantages such as high speed, portability, continuity, and so on. Therefore, the optical tomography technology has high value for research.Firstly, the forward problem and the inverse problem of optical tomography are described in detail in this thesis. For forward problem, the diffusion equation is used as the photon propagation model, and the diffusion equation is solved using finite element method. In the inverse problem, linear method is utilized to reconstruct the image. Further, the regularization parameter is introduced to improve the ill-posedness of the image reconstruction process, and thus to improve the quality of image reconstruction.However, a great amount of calculations are needed for image reconstruction. In this thesis, in order to improve the efficiency of image reconstruction, a reconstruction method is proposed based on the simplified Jacobian matrix. In this method, Jacobian matrix is simplified to reduce the scale of matrix in inverse reconstruction, and hence to reduce the computational requirements. Then, a method based on the reduced measurement data is proposed. The measurement data which has little effect on the precision of image reconstruction is removed. Therefore the data of inverse process is reduced, greatly reducing the time requirements for the inverse problem. The experimental results show that, these methods are able to improve the speed of image reconstruction with high accuracy of the image, greatly improving the efficiency of the reconstruction. |
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