Xia Y
Department of Physics and Institute of Biochemistry and Biotechnology, Oakland University, Rochester, Michigan 48309, USA.
Magn Reson Med. 1998 Jun;39(6):941-9. doi: 10.1002/mrm.1910390612.
To study the structural anisotropy and the magic-angle effect in articular cartilage, T1 and T2 images were constructed at a series of orientations of cartilage specimens in the magnetic field by using NMR microscopy (muMRI). An isotropic T1 and a strong anisotropic T2 were observed across the cartilage tissue thickness. Three distinct regions in the microscopic MR images corresponded approximately to the superficial, transitional, and radial histological zones in the cartilage. The percentage decrease of T2 follows the pattern of the curve of (3cos2theta - 1)2 at the radial zone, where the collagen fibrils are perpendicular to the articular surface. In contrast, little orientational dependence of T2 was observed at the transitional zone, where the collagen fibrils are more randomly oriented. The result suggests that the interactions between water molecules and proteoglycans have a directional nature, which is somehow influenced by collagen fibril orientation. Hence, T2 anisotropy could serve as a sensitive and noninvasive marker for molecular-level orientations in articular cartilage.
为了研究关节软骨的结构各向异性和魔角效应，通过使用核磁共振显微镜（μMRI），在磁场中软骨标本的一系列取向上构建了T1和T2图像。在整个软骨组织厚度上观察到各向同性的T1和强烈各向异性的T2。微观磁共振图像中的三个不同区域大致对应于软骨中的表层、过渡层和放射状组织学区域。在放射状区域，T2的百分比下降遵循(3cos2θ - 1)2曲线的模式，在该区域胶原纤维垂直于关节表面。相比之下，在过渡区域观察到T2的取向依赖性很小，在该区域胶原纤维的取向更为随机。结果表明，水分子与蛋白聚糖之间的相互作用具有方向性，这在某种程度上受胶原纤维取向的影响。因此，T2各向异性可作为关节软骨分子水平取向的敏感且无创的标志物。
