Du Jiang, Pak Byung C, Znamirowski Richard, Statum Sheronda, Takahashi Atsushi, Chung Christine B, Bydder Graeme M
Department of Radiology, University of California, San Diego, CA 92103-8756, USA.
Magn Reson Imaging. 2009 May;27(4):557-64. doi: 10.1016/j.mri.2008.09.003. Epub 2008 Nov 20.
Collagen fibers in tendons and entheses are highly ordered. The protons within the bound water are subject to dipolar interactions whose strength depends on the orientation of the fibers to the static magnetic field B(0). Clinical pulse sequences have been employed to investigate this magic angle effect of the Achilles tendon, but only limited to imaging appearance with a signal void at many angular orientations due to its short T2. Here we investigated the magic angle effect of the Achilles tendons and entheses on a clinical 3-T scanner using clinical sequences as well as an ultrashort TE sequence with a minimal TE of 8 micros. Qualitative and quantitative investigation of the angular-dependent imaging appearance, T1 and T2* values were performed on five ankle specimens. There was a significant increase in signal intensity for all pulse sequences near the magic angle. Mean T2* for tendon increased from 1.94+/-0.28 ms at 0 degrees relative to the B(0) field to 15.25+/-2.13 ms at 55 degrees, and mean T1 increased from 598+/-37 ms at 0 degrees to 621+/-44 ms at 55 degrees. There was less magic angle effect for enthesis whose mean T2* increased from 4.12+/-0.37 ms at 0 degrees to 12.46+/-1.78 ms at 55 degrees, and mean T1 increased from 685+/-41 ms at 0 degrees to 718+/-56 ms at 55 degrees.
肌腱和附着点处的胶原纤维高度有序。结合水中的质子会受到偶极相互作用，其强度取决于纤维相对于静磁场B(0)的方向。临床脉冲序列已被用于研究跟腱的这种魔角效应，但由于其T2较短，在许多角度方向上成像表现为信号缺失，研究仅局限于此。在此，我们使用临床序列以及最短TE为8微秒的超短TE序列，在临床3-T扫描仪上研究了跟腱和附着点的魔角效应。对五个踝关节标本进行了角度依赖性成像表现、T1和T2值的定性和定量研究。在魔角附近，所有脉冲序列的信号强度均显著增加。肌腱的平均T2从相对于B(0)场0度时的1.94±0.28毫秒增加到55度时的15.25±2.13毫秒，平均T1从0度时的598±37毫秒增加到55度时的621±44毫秒。附着点的魔角效应较小，其平均T2*从0度时的4.12±0.37毫秒增加到55度时的12.46±1.78毫秒，平均T1从0度时的685±41毫秒增加到55度时的718±56毫秒。
