Abdullah Osama M, Seidel Thomas, Dahl MarJanna, Gomez Arnold David, Yiep Gavin, Cortino Julia, Sachse Frank B, Albertine Kurt H, Hsu Edward W
Department of Bioengineering, University of Utah, Salt Lake City, UT, USA.
Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA.
NMR Biomed. 2016 Oct;29(10):1338-49. doi: 10.1002/nbm.3576. Epub 2016 Aug 3.
Diffusion tensor imaging (DTI) has emerged as a promising method for noninvasive quantification of myocardial microstructure. However, the origin and behavior of DTI measurements during myocardial normal development and remodeling remain poorly understood. In this work, conventional and bicompartmental DTI in addition to three-dimensional histological correlation were performed in a sheep model of myocardial development from third trimester to postnatal 5 months of age. Comparing the earliest time points in the third trimester with the postnatal 5 month group, the scalar transverse diffusivities preferentially increased in both left ventricle (LV) and right ventricle (RV): secondary eigenvalues D2 increased by 54% (LV) and 36% (RV), whereas tertiary eigenvalues D3 increased by 85% (LV) and 67% (RV). The longitudinal diffusivity D1 changes were small, which led to a decrease in fractional anisotropy by 41% (LV) and 33% (RV) in 5 month versus fetal hearts. Histological analysis suggested that myocardial development is associated with hyperplasia in the early stages of the third trimester followed by myocyte growth in the later stages up to 5 months of age (increased average myocyte width by 198%, myocyte length by 128%, and decreased nucleus density by 70% between preterm and postnatal 5 month hearts.) In a few histological samples (N = 6), correlations were observed between DTI longitudinal diffusivity and myocyte length (r = 0.86, P < 0.05), and transverse diffusivity and myocyte width (r = 0.96, P < 0.01). Linear regression analysis showed that transverse diffusivities are more affected by changes in myocyte size and nucleus density changes than longitudinal diffusivities, which is consistent with predictions of classical models of diffusion in porous media. Furthermore, primary and secondary DTI eigenvectors during development changed significantly. Collectively, the findings demonstrate a role for DTI to monitor and quantify myocardial development, and potentially cardiac disease. Copyright © 2016 John Wiley & Sons, Ltd.
扩散张量成像（DTI）已成为一种很有前景的无创量化心肌微观结构的方法。然而，在心肌正常发育和重塑过程中DTI测量值的起源和变化仍知之甚少。在这项研究中，我们对从妊娠晚期到出生后5个月的绵羊心肌发育模型进行了传统和双室DTI检查，并结合三维组织学相关性分析。将妊娠晚期的最早时间点与出生后5个月组进行比较，左心室（LV）和右心室（RV）的标量横向扩散率均优先增加：第二特征值D2在LV增加了54%，在RV增加了36%；而第三特征值D3在LV增加了85%，在RV增加了67%。纵向扩散率D1变化较小，这导致5个月大的心脏与胎儿心脏相比，LV的各向异性分数降低了41%，RV降低了33%。组织学分析表明，心肌发育在妊娠晚期早期与增生有关，随后在出生后5个月大之前的后期阶段与心肌细胞生长有关（早产心脏与出生后5个月大的心脏相比，平均心肌细胞宽度增加了198%，心肌细胞长度增加了128%，核密度降低了70%）。在少数组织学样本（N = 6）中，观察到DTI纵向扩散率与心肌细胞长度之间存在相关性（r = 0.86，P < 0.05），横向扩散率与心肌细胞宽度之间存在相关性（r = 0.96，P < 0.01）。线性回归分析表明，横向扩散率比纵向扩散率更容易受到心肌细胞大小和核密度变化的影响，这与多孔介质中扩散的经典模型预测一致。此外，发育过程中的主要和次要DTI特征向量发生了显著变化。总的来说，这些发现证明了DTI在监测和量化心肌发育以及潜在的心脏疾病方面的作用。版权所有© 2016 John Wiley & Sons, Ltd.
