IEEE Trans Med Imaging. 2017 Jun;36(6):1316-1325. doi: 10.1109/TMI.2017.2679809. Epub 2017 Mar 10.
A model of cardiac microstructure and diffusion MRI is presented, and compared with experimental data from ex vivo rat hearts. The model includes a simplified representation of individual cells, with physiologically correct cell size and orientation, as well as intra- to extracellular volume ratio. Diffusion MRI is simulated using a Monte Carlo model and realistic MRI sequences. The results show good correspondence between the simulated and experimental MRI signals. Similar patterns are observed in the eigenvalues of the diffusion tensor, the mean diffusivity (MD), and the fractional anisotropy (FA). A sensitivity analysis shows that the diffusivity is the dominant influence on all three eigenvalues of the diffusion tensor, the MD, and the FA. The area and aspect ratio of the cell cross-section affect the secondary and tertiary eigenvalues, and hence the FA. Within biological norms, the cell length, volume fraction of cells, and rate of change of helix angle play a relatively small role in influencing tissue diffusion. Results suggest that the model could be used to improve understanding of the relationship between cardiac microstructure and diffusion MRI measurements, as well as in testing and refinement of cardiac diffusion MRI protocols.
提出了一种心脏微结构和扩散 MRI 的模型，并与离体大鼠心脏的实验数据进行了比较。该模型包括对单个细胞的简化表示，具有生理上正确的细胞大小和方向，以及细胞内外体积比。使用蒙特卡罗模型和真实的 MRI 序列模拟扩散 MRI。结果表明，模拟和实验 MRI 信号之间具有良好的一致性。在扩散张量的特征值、平均扩散系数（MD）和各向异性分数（FA）中观察到相似的模式。敏感性分析表明，扩散是对扩散张量的所有三个特征值、MD 和 FA 的主要影响因素。细胞横截面的面积和纵横比会影响次要和三次特征值，从而影响 FA。在生物学范围内，细胞长度、细胞体积分数和螺旋角变化率对组织扩散的影响相对较小。结果表明，该模型可用于提高对心脏微结构和扩散 MRI 测量之间关系的理解，以及在心脏扩散 MRI 方案的测试和改进中。
