School of Computer and Information Technology, Beijing Jiaotong University, Beijing, People's Republic of China. Univ Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1206, F-69621, LYON, France. Author to whom any correspondence should be addressed.
Phys Med Biol. 2018 Oct 23;63(21):215003. doi: 10.1088/1361-6560/aae514.
Diffusion tensor imaging (DTI) is a non-invasive technique used to obtain the 3D fiber structure of whole human hearts, for both in vivo and ex vivo cases. However, by essence, DTI does not measure directly the orientations of myocardial fibers. In contrast, polarized light imaging (PLI) allows for physical measurements of fiber orientations, but only for ex vivo case. This work aims at quantitatively comparing the myocardial fiber orientations of whole human hearts obtained from cardiac DTI with those measured by PLI. Whole human neonatal and infant hearts were first imaged using DTI. The same whole hearts were then imaged using PLI. After DTI and PLI data are registered, the orientations of fibers from the two imaging modalities were finally quantitatively compared. The results show that DTI and PLI have similar variation patterns of elevation and azimuth angles, with some differences in transmural elevation angle range. DTI itself induces an underestimation of the range of transmural elevation angles by a factor of about 25° at the basal and equatorial slices and the reduction of spatial resolution further decreases this range. PLI data exhibit a 15° ± 5° (P < 0.01) narrower transmural elevation angle range at apical slices than in basal or equatorial slices. This phenomenon is not observed in DTI data. In both modalities, the azimuth angle maps exhibit curved or twisting boundaries at the basal and apical slices. The experimental results globally enforce DTI as a valid imaging technique to reasonably characterize fiber orientations of the human heart noninvasively.
弥散张量成像（DTI）是一种非侵入性技术，用于获取整个人体心脏的 3D 纤维结构，无论是在体还是离体情况。然而，本质上，DTI 并不能直接测量心肌纤维的方向。相比之下，偏振光成像（PLI）允许对纤维方向进行物理测量，但仅适用于离体情况。本工作旨在定量比较通过心脏 DTI 获得的整个人体心脏的心肌纤维方向与通过 PLI 测量的纤维方向。首先使用 DTI 对整个新生儿和婴儿心脏进行成像。然后，使用 PLI 对同一整个心脏进行成像。在 DTI 和 PLI 数据配准后，最终定量比较了两种成像方式的纤维方向。结果表明，DTI 和 PLI 具有相似的升高和方位角变化模式，但在壁内升高角范围上存在一些差异。DTI 本身会导致基底和赤道切片的壁内升高角范围低估约 25°，而空间分辨率的降低进一步减小了该范围。PLI 数据在 apical 切片上表现出比基底或赤道切片窄 15°±5°（P<0.01）的壁内升高角范围。这种现象在 DTI 数据中没有观察到。在两种模态中，方位角图在基底和 apical 切片上显示出弯曲或扭曲的边界。实验结果总体上证明 DTI 是一种有效的成像技术，可以合理地非侵入性地描述人体心脏的纤维方向。
