Moore C C, McVeigh E R, Zerhouni E A
Departments of Radiology and Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
J Cardiovasc Magn Reson. 1999;1(3):207-22. doi: 10.3109/10976649909088333.
The purpose of this study was to investigate the relationship between three-dimensional (3D) deformation patterns in the canine left ventricle and localized graded reductions in perfusion. Magnetic resonance (MR) tissue tagging in a clinical scanner was used to determine systolic 3D deformation throughout the left ventricle with 32-msec time resolution. Six dogs were studied at normal and reduced left anterior descending coronary artery flow levels, for a total of 14 studies. Deformation was calculated by fitting a 3D displacement field to tag displacement data from three orthogonal sets of tags and taking spatial derivatives. A novel index of 3D radial mechanical function, calculated from the 3D strain tensor components and the tissue incompressibility constraint, had a higher correlation (R = 0.94) with perfusion (colored microspheres) than any of the 3D Lagrangian finite strain tensor components or wall thickening. As a function of the fraction of baseline perfusion, it was well fit by a linear relationship for subnormal perfusion with a slope of 0.46 +/- 0.05 and an intercept of -0.156 +/- 0.026. Longitudinal strain was lost first with decreasing perfusion (48%), followed by circumferential (40%) and finally radial function (35%). The strain method detected perfusion drops as small as 20%, and early paradoxical strain transients lasting 100 msec were seen only with ischemia. 3D strain changes can be noninvasively measured throughout the left ventricle with MR tissue tagging. MR imaging-derived strain indices, unique to 3D analysis, correlate most sensitively with regional perfusion in the canine left ventricle.
本研究的目的是调查犬左心室的三维（3D）变形模式与局部灌注分级降低之间的关系。在临床扫描仪中使用磁共振（MR）组织标记技术，以32毫秒的时间分辨率确定整个左心室的收缩期3D变形。对6只犬在正常和左前降支冠状动脉血流水平降低的情况下进行了研究，共进行了14项研究。通过将三维位移场拟合到来自三组正交标记的标记位移数据并进行空间导数计算来得出变形。一种根据三维应变张量分量和组织不可压缩性约束计算得出的新型三维径向力学功能指数，与灌注（彩色微球）的相关性（R = 0.94）高于任何三维拉格朗日有限应变张量分量或壁增厚。作为基线灌注分数的函数，对于灌注低于正常水平的情况，它与线性关系拟合良好，斜率为0.46±0.05，截距为 -0.156±0.026。随着灌注降低，纵向应变首先丧失（48%），其次是圆周应变（40%），最后是径向功能（35%）。应变方法能够检测到低至20%的灌注下降，并且仅在缺血时才会出现持续100毫秒的早期矛盾应变瞬变。通过MR组织标记可以在整个左心室内无创地测量三维应变变化。MR成像衍生的应变指数是三维分析所特有的，与犬左心室的区域灌注最敏感相关。
