Yale University, New Haven, CT 06510, USA.
Cardiovasc Diagn Ther. 2014 Apr;4(2):56-63. doi: 10.3978/j.issn.2223-3652.2013.10.02.
The objective of this study is to determine the normal value of 3D left ventricular (LV) twist in subendocardial, mid-wall and subepicardial layers, as well as to study the effects of aging on 3D LV twist by tagged MR motion tracking techniques. Three dimensional motion detection based on 3D tagged MR images is robust to out-of-plane motion error; while 2D motion detection is inherently unable to analyze the 3D cardiac motion and may lead to inaccurate results.
The 3D LV volumetric images were acquired in 52 normal adult subjects (aged 21-82) and were analyzed by using 3D HARmonic phase (HARP) technique. HARP technique provided the 3D displacement fields and the displacements were utilized to compute the rotational values. LV twist was defined as apical rotation relative to the basal rotation, in the 3D coordinates. The LV twist values of subendocardial, mid-wall and subepicardial layers were analyzed separately. The measured parameters in this study were: peak apical rotation, peak basal rotation, and peak LV twist.
Looking at the apex, the normal LV maintains a clockwise rotation in the LV basal plane and a counterclockwise rotation in the LV apical plane. In general, the apical and basal rotation values increase during the aging process, leading to an increased value of LV twist. Peak epicardial LV twist is (10.4±2.6 degrees) which is lower than the mid-wall LV twist (11.3±2.2 degrees) and endocardial LV twist (12.1±2.6 degrees) in the young group (21-35 years old). Also, peak epicardial LV twist is (12.2±2.6 degrees) which is lower than the mid-wall LV twist (14.4±2.8 degrees) and endocardial LV twist (14.7±2.5 degrees) in the middle aged group (21-35 years old). In a similar way, peak epicardial LV twist is (14.8±2.9 degrees) which is lower than the mid-wall LV twist (15.7±3.6 degrees) and endocardial LV twist (16.7±3.0 degrees) in the old group (50-65 years old). Regarding the older group (more than 65 years old), peak epicardial LV twist is (15.9±3.1 degrees) which is lower than the mid-wall LV twist (16.2±3.4 degrees) and endocardial LV twist (18.3±3.0 degrees).
It is feasible to measure the subepicardial, mid-wall and subendocardial twist in tagged MR images. The twist value gradually increases in the aging process. Outside layers have greater twist values compared to the inside layers.
本研究旨在确定心内膜下、中层和心外膜下 3D 左心室（LV）扭转的正常值，并通过标记 MR 运动跟踪技术研究年龄对 3D LV 扭转的影响。基于 3D 标记 MR 图像的三维运动检测对离面运动误差具有很强的鲁棒性；而二维运动检测则无法对 3D 心脏运动进行分析，可能导致结果不准确。
本研究纳入了 52 例正常成年受试者（年龄 21-82 岁），使用 3D HARmonic phase（HARP）技术获取 3D LV 容积图像。HARP 技术提供了 3D 位移场，利用这些位移来计算旋转值。分别分析心内膜下、中层和心外膜下各层的 LV 扭转值。本研究测量的参数包括：心尖旋转峰值、基底旋转峰值和 LV 扭转峰值。
从心尖观察，正常 LV 在 LV 基底平面呈顺时针旋转，在 LV 心尖平面呈逆时针旋转。一般来说，随着年龄的增长，心尖和基底的旋转值增加，导致 LV 扭转值增加。心外膜 LV 扭转峰值为（10.4±2.6）°，低于年轻组（21-35 岁）心外膜（12.1±2.6）°、中层（11.3±2.2）°和心内膜（12.1±2.6）°。同样，心外膜 LV 扭转峰值（12.2±2.6）°也低于中年组（21-35 岁）心外膜（14.4±2.8）°、中层（14.7±2.5）°和心内膜（14.7±2.5）°。同样，心外膜 LV 扭转峰值（14.8±2.9）°也低于老年组（50-65 岁）心外膜（15.7±3.6）°、中层（15.7±3.6）°和心内膜（16.7±3.0）°。对于年龄更大的组（>65 岁），心外膜 LV 扭转峰值（15.9±3.1）°低于中层（16.2±3.4）°和心内膜（18.3±3.0）°。
在标记 MR 图像上测量心外膜下、中层和心内膜下扭转是可行的。随着年龄的增长，扭转值逐渐增加。外层的扭转值大于内层。
