Hardy P A
Division of Radiology, Cleveland Clinic Foundation, OH 44195, USA.
Radiology. 1996 Jul;200(1):143-7. doi: 10.1148/radiology.200.1.8657902.
To demonstrate and quantitate the magic angle effect in the intervertebral disk.
Magnetic resonance (MR) images of a lumbar intervertebral disk in a healthy volunteer were obtained with MR images with horizontal and vertical magnetic fields. Thin-section spin-echo images of an excised intervertebral disk were obtained with a horizontal field machine at orientations with respect to the main magnetic field between +90 degrees and -90 degrees. T1 and T2 were measured independently in this disk at two orientations.
Images of the in vivo disk demonstrated a variation in the signal intensity of the anulus fibrosus that was different for the two MR units. The images obtained in the excised intervertebral disk demonstrated a signal intensity variation with disk orientation that was most pronounced in the anterior portion of the anulus. Relaxation time measurements showed the signal intensity reduction to arise from a reduction in T2 with oblique orientations.
The observed signal intensity variation with disk orientation arises from an anisotropy in T2 caused by the restriction of water associated with collagen in the anulus. The magic angle effect in intervertebral disks will be observed with vertical magnetic field MR imagers.
证明并量化椎间盘的魔角效应。
在一名健康志愿者身上获取腰椎间盘的磁共振（MR）图像，使用具有水平和垂直磁场的MR成像。在一台水平磁场机器上，以相对于主磁场+90度至-90度的方向获取切除椎间盘的薄层自旋回波图像。在该椎间盘的两个方向上独立测量T1和T2。
体内椎间盘图像显示，两个MR设备所呈现的纤维环信号强度存在差异。在切除的椎间盘中获得的图像显示，信号强度随椎间盘方向而变化，在纤维环前部最为明显。弛豫时间测量表明，信号强度降低是由于倾斜方向时T2降低所致。
观察到的信号强度随椎间盘方向的变化是由纤维环中与胶原相关的水的限制导致的T2各向异性引起的。垂直磁场MR成像仪将观察到椎间盘中的魔角效应。
