Key Laboratory of Intelligent Medical Image Analysis and Precise Diagnosis of Guizhou Province, College of Computer Science and Technology, Guizhou University, Guiyang 550025, China.
Key Laboratory of Intelligent Medical Image Analysis and Precise Diagnosis of Guizhou Province, College of Computer Science and Technology, Guizhou University, Guiyang 550025, China.
Med Image Anal. 2022 Apr;77:102325. doi: 10.1016/j.media.2021.102325. Epub 2022 Feb 5.
To investigate the relationship between microscopic myocardial structures and macroscopic measurements of diffusion tensor imaging (DTI), we proposed a cardiac DTI simulation method using the Bloch equation and the Monte Carlo random walk in a realistic myocardium model reconstructed from polarized light imaging (PLI) data of the entire human heart. To obtain a realistic simulation, with the constraints of prior knowledge pertaining to the maturational change of the myocardium structure, appropriate microstructure modeling parameters were iteratively determined by matching DTI simulations and real acquisitions of the same hearts in terms of helix angle, fractional anisotropy (FA) and mean diffusivity (MD) maps. Once a realistic simulation was obtained, we varied the extra-cellular volume (ECV) ratio, myocyte orientation heterogeneity and myocyte size, and explored the effects of microscopic changes in tissue structure on macroscopic diffusion metrics. The experimental results demonstrated the feasibility of simulating the DTI of the whole heart using PLI measurements. When varying ECV from 15% to 55%, mean FA decreased from 0.55 to 0.26, axial diffusivity increased by 0.6 μm/ms, and radial diffusivity increased by 0.7 μm/ms. When orientation heterogeneity was varied from 0 to 20, mean FA decreased from 0.4 to 0.3, axial diffusivity decreased by 0.08 μm/ms, and radial diffusivity increased by 0.03 μm/ms. When mean diameter of myocytes was varied from 6 μm to 10 μm, FA decreased from 0.67 to 0.46, axial and radial diffusivities increased by 0.05 and 0.2 μm/ms, respectively.
为了研究扩散张量成像（DTI）的微观心肌结构与宏观测量之间的关系，我们提出了一种基于 Bloch 方程和 Monte Carlo 随机漫步的心脏 DTI 模拟方法，该方法使用从偏光成像（PLI）数据重建的整个心脏的现实心肌模型。为了获得现实的模拟，根据心肌结构成熟变化的先验知识，通过将 DTI 模拟与相同心脏的真实采集在螺旋角、各向异性分数（FA）和平均扩散系数（MD）图方面进行匹配，迭代确定适当的微观结构建模参数。一旦获得了现实的模拟，我们就会改变细胞外体积（ECV）比、心肌细胞取向异质性和心肌细胞大小，并探讨组织结构微观变化对宏观扩散指标的影响。实验结果表明，使用 PLI 测量值模拟整个心脏的 DTI 是可行的。当 ECV 从 15%变化到 55%时，平均 FA 从 0.55 降低到 0.26，轴向扩散系数增加了 0.6μm/ms，径向扩散系数增加了 0.7μm/ms。当取向异质性从 0 变化到 20 时，平均 FA 从 0.4 降低到 0.3，轴向扩散系数降低了 0.08μm/ms，径向扩散系数增加了 0.03μm/ms。当心肌细胞的平均直径从 6μm 变化到 10μm 时，FA 从 0.67 降低到 0.46，轴向和径向扩散系数分别增加了 0.05μm/ms 和 0.2μm/ms。
