Young A A, Imai H, Chang C N, Axel L
Department of Radiology, Hospital of the University of Pennsylvania, Pa.
Circulation. 1994 Feb;89(2):740-52. doi: 10.1161/01.cir.89.2.740.
Myocardial tissue tagging with the use of magnetic resonance imaging allows noninvasive regional analysis of heart wall motion and deformation. However, any evaluation of the effect of disease or treatment requires a baseline reference of normal values and variation. We studied the two-dimensional motion of material points imaged within the left ventricular wall using spatial modulation of magnetization (SPAMM) in 12 normal human volunteers.
Five parallel short-axis and five parallel long-axis slices were acquired at five times during systole. SPAMM tags were generated at end diastole using a 7-mm grid. Intersection point data were analyzed for displacement, rotation, and torsion, and triangles of points were analyzed for local rotation and principal strains. Short-axis displacement was the least in the septum for all longitudinal levels (P < .001). Torsion about the long axis was uniform circumferentially because of the motion of the centroids used to reference the rotation. In the long-axis images, the base displaced longitudinally toward the apex, with the posterior wall moving farther than the anterior wall (13.4 +/- 2.2 versus 9.7 +/- 1.8 mm, P < .001) in this direction. The largest principal strain (maximum lengthening) was approximately radially oriented in both views. In the short-axis images, the minimum principal strain (maximum shortening) increased in magnitude toward the apex (P < .001) with little circumferential variation, except at midventricle, where the anterior wall showed greater contraction than the posterior wall (-0.21 +/- 0.03 versus -0.19 +/- 0.02, P < .02).
Consistent regional variations in deformation are seen in the normal human heart. Displacement and maximum shortening strains are well characterized with two-dimensional magnetic resonance tagging; however, higher-resolution images will be required to study transmural variations.
利用磁共振成像进行心肌组织标记可对心脏壁运动和变形进行无创区域分析。然而，对疾病或治疗效果的任何评估都需要正常数值及其变化的基线参考。我们使用磁化空间调制（SPAMM）技术对12名正常人类志愿者左心室壁内成像的物质点的二维运动进行了研究。
在收缩期的五个时间点采集了五个平行短轴和五个平行长轴切片。在舒张末期使用7毫米网格生成SPAMM标记。对交点数据进行位移、旋转和扭转分析，对点子三角形进行局部旋转和主应变分析。在所有纵向层面，短轴位移在室间隔最小（P <.001）。由于用于参考旋转的质心运动，围绕长轴的扭转在圆周上是均匀的。在长轴图像中，基部沿纵向向心尖移位，后壁在该方向上比前壁移动得更远（13.4±2.2对9.7±1.8毫米，P <.001）。在两个视图中，最大主应变（最大伸长）大致呈径向取向。在短轴图像中，最小主应变（最大缩短）的大小向心尖增加（P <.001），圆周变化很小，除了心室中部，那里前壁的收缩大于后壁（-0.21±0.03对-0.19±0.02，P <.02）。
在正常人体心脏中可看到变形的一致区域差异。二维磁共振标记能很好地表征位移和最大缩短应变；然而，需要更高分辨率的图像来研究透壁变化。
