Suever Jonathan D, Wehner Gregory J, Jing Linyuan, Powell David K, Hamlet Sean M, Grabau Jonathan D, Mojsejenko Dimitri, Andres Kristin N, Haggerty Christopher M, Fornwalt Brandon K
IEEE Trans Med Imaging. 2017 May;36(5):1076-1085. doi: 10.1109/TMI.2016.2646321. Epub 2016 Dec 29.
Mechanics of the left ventricle (LV) are important indicators of cardiac function. The role of right ventricular (RV) mechanics is largely unknown due to the technical limitations of imaging its thin wall and complex geometry and motion. By combining 3D Displacement Encoding with Stimulated Echoes (DENSE) with a post-processing pipeline that includes a local coordinate system, it is possible to quantify RV strain, torsion, and synchrony. In this study, we sought to characterize RV mechanics in 50 healthy individuals and compare these values to their LV counterparts. For each cardiac frame, 3D displacements were fit to continuous and differentiable radial basis functions, allowing for the computation of the 3D Cartesian Lagrangian strain tensor at any myocardial point. The geometry of the RV was extracted via a surface fit to manually delineated endocardial contours. Throughout the RV, a local coordinate system was used to transform from a Cartesian strain tensor to a polar strain tensor. It was then possible to compute peak RV torsion as well as peak longitudinal and circumferential strain. A comparable analysis was performed for the LV. Dyssynchrony was computed from the standard deviation of regional activation times. Global circumferential strain was comparable between the RV and LV (-18.0% for both) while longitudinal strain was greater in the RV (-18.1% vs. -15.7%). RV torsion was comparable to LV torsion (6.2 vs. 7.1 degrees, respectively). Regional activation times indicated that the RV contracted later but more synchronously than the LV. 3D spiral cine DENSE combined with a post-processing pipeline that includes a local coordinate system can resolve both the complex geometry and 3D motion of the RV.
左心室(LV)力学是心脏功能的重要指标。由于右心室(RV)薄壁、复杂几何形状和运动的成像技术限制,其力学作用在很大程度上尚不清楚。通过将三维位移编码与受激回波(DENSE)相结合,并采用包括局部坐标系的后处理管道,可以量化右心室应变、扭转和同步性。在本研究中,我们试图描述50名健康个体的右心室力学特征,并将这些值与其左心室对应值进行比较。对于每个心脏帧,将三维位移拟合到连续且可微的径向基函数,从而能够计算任何心肌点处的三维笛卡尔拉格朗日应变张量。通过对手动描绘的心内膜轮廓进行表面拟合来提取右心室的几何形状。在整个右心室中,使用局部坐标系将笛卡尔应变张量转换为极坐标应变张量。然后可以计算右心室峰值扭转以及峰值纵向和圆周应变。对左心室进行了类似的分析。根据区域激活时间的标准差计算不同步性。右心室和左心室的整体圆周应变相当(均为-18.0%),而右心室的纵向应变更大(-18.1%对-15.7%)。右心室扭转与左心室扭转相当(分别为6.2度和7.1度)。区域激活时间表明,右心室收缩比左心室晚,但更同步。三维螺旋电影DENSE与包括局部坐标系的后处理管道相结合,可以解析右心室的复杂几何形状和三维运动。