A Finite Element Mesh Regrouping Strategy-Based Hybrid Light Transport Model for Enhancing the Efficiency and Accuracy of XLCT.
A Finite Element Mesh Regrouping Strategy-Based Hybrid Light Transport Model for Enhancing the Efficiency and Accuracy of XLCT.
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基于有限元网格重组策略的混合光传输模型，提高 XLCT 的效率和精度
DOI：
10.3389/fonc.2021.751139
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发表时间：
2021
影响因子：
4.7
通讯作者：
He X
中科院分区：
文献类型：
--
作者：
Liu Y;Hu X;Chu M;Guo H;Yu J;He X
X射线发光计算机层析成像(XLCT)是光学分子成像中一种新兴的混合成像方式，受到了越来越多的关注和广泛的研究。在XLCT中，光传输模型的精度和运算效率对光源的快速准确重建起着决定性的作用。为了模拟XLCT中的光传输特性，考虑到扩散方程(DE)的局限性和简化球谐近似方程(SPN)的时间和存储开销，需要建立混合光传输模型。De模型和SPN模型分别是RTE的一阶和高阶近似。由于DE模型和SPN模型在求解过程中区域的不连续性，以及两种模型构造的系统矩阵维度的不一致，混合光传输模型的系统矩阵构造是一个亟待解决的问题。提出了一种新的基于有限元网格重组策略的XLCT混合光传输模型。首先，基于有限元网格重组策略，得到两个独立的网格。因此，对于DE和SP N模型，可以在两个相应的网格系统中分别计算系统矩阵和源权重矩阵。同时，可以将一些并行计算策略与有限元网格重组策略相结合，进一步节省系统矩阵的计算时间。然后，根据混合边界条件对两个不同维度的系统矩阵进行重复结点处理，将两个网格合并为一个重组网格，建立混合光传输模型。此外，与以前提出的混合光传输模型相比，该方法可以减少计算内存消耗，实现计算精度和效率之间的良好平衡。正演数值仿真结果表明，该方法具有较好的传输精度，实现了效率与精度的平衡。反向仿真结果表明，该方法在源重建中具有较高的定位精度、形态恢复能力和图像对比度。体内实验验证了该方法的实用性和有效性。
X-ray luminescence computed tomography (XLCT) is an emerging hybrid imaging modality in optical molecular imaging, which has attracted more attention and has been widely studied. In XLCT, the accuracy and operational efficiency of an optical transmission model play a decisive role in the rapid and accurate reconstruction of light sources. For simulation of optical transmission characteristics in XLCT, considering the limitations of the diffusion equation (DE) and the time and memory costs of simplified spherical harmonic approximation equation (SPN ), a hybrid light transport model needs to be built. DE and SPN models are first-order and higher-order approximations of RTE, respectively. Due to the discontinuity of the regions using the DE and SPN models and the inconsistencies of the system matrix dimensions constructed by the two models in the solving process, the system matrix construction of a hybrid light transmission model is a problem to be solved. We provided a new finite element mesh regrouping strategy-based hybrid light transport model for XLCT. Firstly, based on the finite element mesh regrouping strategy, two separate meshes can be obtained. Thus, for DE and SP N models, the system matrixes and source weight matrixes can be calculated separately in two respective mesh systems. Meanwhile, some parallel computation strategy can be combined with finite element mesh regrouping strategy to further save the system matrix calculation time. Then, the two system matrixes with different dimensions were coupled though repeated nodes were processed according to the hybrid boundary conditions, the two meshes were combined into a regrouping mesh, and the hybrid optical transmission model was established. In addition, the proposed method can reduce the computational memory consumption than the previously proposed hybrid light transport model achieving good balance between computational accuracy and efficiency. The forward numerical simulation results showed that the proposed method had better transmission accuracy and achieved a balance between efficiency and accuracy. The reverse simulation results showed that the proposed method had superior location accuracy, morphological recovery capability, and image contrast capability in source reconstruction. In-vivo experiments verified the practicability and effectiveness of the proposed method.
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