Rump Jens, Braun Jürgen, Papazoglou Sebastian, Taupitz Matthias, Sack Ingolf
Institute of Radiology, Charité-University Medicine Berlin, Berlin, Germany.
J Magn Reson Imaging. 2006 Apr;23(4):541-6. doi: 10.1002/jmri.20534.
To demonstrate reciprocal changes of the apparent proton-T2 time in the biceps and triceps due to passive contraction and extension of the muscle fibers.
The contraction state of the upper arm muscles of six healthy volunteers was passively changed by alternating the forearm position between the straight-arm position and an elbow flexion of 90 degrees. The relaxation of the muscle during passive contraction and extension was measured with the use of muscle electromyography (EMG) experiments. Spin-echo (SE) MRI with increasing echo times (TEs) of 12-90 msec was used to acquire the averaged signal decay of the segmented biceps and triceps. The apparent T2 was deduced using monoexponential least-square fitting.
The median T2 alterations in biceps and triceps among all volunteers were found to be 1.2 and -1.3 msec in the straight and bent forearm positions, respectively. The confidence intervals (0.5 to 1.7 msec in biceps, and -2.6 to -1.1 msec in triceps) clearly indicate that proton-T2 in MR images is significantly (P < 0.05) prolonged with muscle contraction.
The observed increase of the proton-T2 time was correlated with a passive contraction of skeletal muscle fibers. This passive effect can be attributed to changes in the intracellular water mobility corresponding to the well-known "active" T2 increase that occurs after stimulation of muscle.
证明由于肌肉纤维的被动收缩和伸展，肱二头肌和肱三头肌中表观质子T2时间的相互变化。
通过在直臂位置和90度肘部屈曲之间交替前臂位置，被动改变6名健康志愿者上臂肌肉的收缩状态。使用肌肉肌电图（EMG）实验测量被动收缩和伸展过程中肌肉的松弛情况。使用回波时间（TE）为12 - 90毫秒且逐渐增加的自旋回波（SE）MRI来获取分割后的肱二头肌和肱三头肌的平均信号衰减。使用单指数最小二乘法拟合推导表观T2。
在所有志愿者中，发现直臂和屈臂位置时肱二头肌和肱三头肌的T2中位数变化分别为1.2毫秒和 - 1.3毫秒。置信区间（肱二头肌为0.5至1.7毫秒，肱三头肌为 - 2.6至 - 1.1毫秒）清楚地表明，MR图像中的质子T2随着肌肉收缩而显著（P < 0.05）延长。
观察到的质子T2时间增加与骨骼肌纤维的被动收缩相关。这种被动效应可归因于细胞内水流动性的变化，这与刺激肌肉后发生的众所周知的“主动”T2增加相对应。
