Zhong Xiaodong, Epstein Frederick H, Spottiswoode Bruce S, Helm Patrick A, Blemker Silvia S
Biomedical Engineering, University of Virginia, Charlottesville, VA, USA.
J Biomech. 2008;41(3):532-40. doi: 10.1016/j.jbiomech.2007.10.026. Epub 2008 Jan 3.
The objective of this study was to apply cine magnetic resonance imaging (MRI) using displacement encoding with stimulated echoes (DENSE) to measure the dynamic two-dimensional (2D) displacement and Lagrangian strain fields in the biceps brachii muscle. Six healthy volunteers underwent cine DENSE MRI during repeated elbow flexion against the load of gravity. Displacement encoded dynamic images of the upper arm were acquired with spatial and temporal resolutions of 1.9 x 1.9 mm(2) and 30 ms, respectively. Pixel-wise Lagrangian displacement and strain fields were calculated from the measured images. We extracted the first and second principal strains (E1 and E2) along the centerline and anterior regions of the muscle. E1 and E2 were relatively uniform along the anterior region. However, E1 and E2 were both non-uniform along the centerline region-normalized values for E1 and E2 varied over the ranges of 0.27-1.35, and 0.45-2.36, respectively. The directions of the first and second principal strains varied throughout the muscle and showed that the direction of principal shortening is not necessarily aligned with fascicle direction. This study demonstrates the utility of cine DENSE MRI for analyzing skeletal muscle mechanics and provides data describing the in vivo mechanics of muscle tissue to a level of detail that has not been previously possible.
本研究的目的是应用使用刺激回波位移编码（DENSE）的电影磁共振成像（MRI）来测量肱二头肌的动态二维（2D）位移和拉格朗日应变场。六名健康志愿者在对抗重力负荷的反复肘部屈曲过程中接受了电影DENSE MRI检查。分别以1.9×1.9 mm²的空间分辨率和30 ms的时间分辨率获取上臂的位移编码动态图像。从测量图像中计算逐像素的拉格朗日位移和应变场。我们沿着肌肉的中心线和前部区域提取了第一和第二主应变（E1和E2）。E1和E2在前部区域相对均匀。然而，E1和E2在中心线区域均不均匀——E1和E2的归一化值分别在0.27 - 1.35和0.45 - 2.36范围内变化。第一和第二主应变的方向在整个肌肉中变化，表明主缩短方向不一定与肌束方向对齐。本研究证明了电影DENSE MRI在分析骨骼肌力学方面的实用性，并提供了描述肌肉组织体内力学的详细数据，其详细程度是以前无法实现的。
