Cone-beam X-ray luminescence computed tomography (CB-XLCT) is a noninvasive molecular imaging technique that reflects the distribution of fluorescent nanomaterials in the imaged object. It is urgent to describe the quantitative relationship between the reconstruction and the concentration of the fluorescent nanomaterials. However, in the field of CB-XLCT, most researches aim to improve the imaging accuracy, ignoring further quantitative evaluation of the reconstruction intensity. In this work, the quantitative evaluation for CB-XLCT is studied. In addition, to improve the quantitative performance, a new strategy based on fast iterative shrinkage-thresholding algorithm (FISTA) and 3D Total- Variation (TV) denoising with Split Bregman (SB) method (FISTA-TV) is proposed for CB-XLCT reconstruction. In FISTA-TV, FISTA is applied to get a L1-regularized sparse reconstruction in CB-XLCT and the Split Bregman method is used to solve the TV denoising problem. With the FISTA-TV strategy, the sparse results yielded by FISTA together with 3D TV denoising based on Split Bregman, alleviate the illness of the inverse problem of CB-XLCT, making the relationship between the reconstruction intensity and the actual concentration of fluorescent nanomaterials more accurate. Computer simulations have shown the quantitative reconstruction and evaluation for CB-XLCT is improved with the proposed FISTA-TV algorithm, compared to Algebraic Reconstruction Technique (ART), Tikhonov regularization, FISTA.
The reconstruction of cone-beam x-ray luminescence computed tomography (CB-XLCT) is an ill-posed inversion problem because of incomplete data and lack of prior information. To improve the illness of the inversion problem, the data fidelity and regularization term are two key aspects for the reconstruction model. However, there is not much research considering the statistical characteristics of data in XLCT reconstruction, although many various regularizations are studied. To make full use of the data noise model, a strategy combing the maximum likelihood expectation estimation (MLEM) algorithm and the regularization-type algorithm is proposed. In the MLEM algorithm, the Poisson noise is considered for accurate data model. The result by the regularization-type algorithm is used as the specific initial image for the MLEM to improve the reconstruction quality and convergence speed of the MLEM. There are two main steps in the proposed strategy. Firstly, the fast iterative shrinkage-thresholding algorithm (FISTA) with a large regularization parameter is used to get the sparse solution quickly. Secondly, the sparse solution is used as the initial iteration value of the MLEM. The proposed algorithm is named as FISTA-MLEM. Through the stepwise strategy, the image sparsity is guaranteed and the accuracy of the reconstruction is maintained. Result of phantom experiment shows the FISTA-MLEM method presents better contrast to noise ratio and shape similarity compared with other traditional methods, such as ART, Tikhonov, FISTA and TSVD.
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