Diffusion tensor imaging has been used for assessing the orientation of cardiac myocytes for decades. Striking methodological differences exist between studies when quantifying these orientations. This limits the comparability between studies, and impedes collaboration and the drawing of appropriate physiological conclusions. We have sought to elucidate these differences, permitting us to propose a standardised "tool set" that might better establish consensus in future studies. We fixed hearts from seven 25 kg pigs in formalin, and scanned them using diffusion tensor imaging. Using various angle definitions as found in literature, we assessed the orientations of cardiomyocytes, comparing them in terms of helical and intrusion angles, along with the orientation of their aggregations. The difference between assessment of the helical angle with and without relation to the epicardial curvature was 25.2° (SD: 7.9) at the base, 5.8° (1.9) at the equatorial level, and 28.0° (7.0) at the apex, ANOVA P = 0.001. In comparable fashion, the intrusion angle differed by 25.9° (12.9), 7.6° (0.98) and 17.5° (4.7), P = 0.01, and the angle of the aggregates (E3-angle) differed by 25.0° (13.5) at the base, 9.4° (1.7) at the equator, and 23.1° (6.2) apically, P = 0.003. When assessing 14 definitions used in literature to calculate the orientation of aggregates, only 4 rendered identical results. The findings show that any attempt to use projection of eigenvectors introduces considerable bias. The epicardial curvature of the ventricular cone needs to be taken into account when seeking to provide accurate quantification of the orientation of the aggregated cardiomyocytes, especially in the apical and basal regions. This means that projection of eigenvectors should be avoided prior to quantifying myocyte orientation, especially when assessing radial orientation. Based on our results, we suggest appropriate methods for valid assessment of myocyte orientation using diffusion tensor imaging.

中文翻译：

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使用扩散张量成像对心肌细胞的方向进行解剖学正确评估。

扩散张量成像已用于评估心肌细胞的方向数十年。在量化这些方向时，研究之间存在惊人的方法学差异。这限制了研究之间的可比性，并阻碍了合作和得出适当的生理结论。我们试图阐明这些差异，使我们能够提出一个标准化的“工具集”，以更好地在未来的研究中建立共识。我们用福尔马林固定了7头25公斤猪的心脏，并使用扩散张量成像对其进行了扫描。使用文献中发现的各种角度定义，我们评估了心肌细胞的方向，将它们在螺旋角和侵入角方面进行了比较，并对其聚集方向进行了比较。ANOVA P，在有或没有心外膜曲率的情况下，螺旋角的评估之间的差异是：在底部为25.2°（SD：7.9），在赤道水平为5.8°（1.9），在顶点为28.0°（7.0） = 0.001。以可比较的方式，侵入角相差25.9°（12.9），7.6°（0.98）和17.5°（4.7），P = 0.01，而聚集体的角度（E3角）在20°C时相差25.0°（13.5）。基准点，赤道为9.4°（1.7），顶端为23.1°（6.2），P = 0.003。在评估文献中使用的14种定义来计算聚集体的方向时，只有4种给出了相同的结果。研究结果表明，使用特征向量投影的任何尝试都会引起相当大的偏差。当试图提供聚集心肌细胞的方向的准确定量时，尤其是在心尖和基底区域，需要考虑心室圆锥的心外膜曲率。这意味着在量化肌细胞方向之前，应避免本征向量的投影，尤其是在评估径向方向时。根据我们的结果，我们建议使用弥散张量成像对肌细胞定向进行有效评估的适当方法。