Evaluation of Internal Structure of the Articular Cartilage in Terms of ^1H-NMR Relaxation Behavior

通过快速反转恢复和多自旋回波磁共振成像（MRI）测量关节软骨的^ 1h纵向（T_1）和横向（T_2）弛豫时间，分析关节软骨的结构特征。从15个股骨内侧髁上分离承重区和非承重区软骨-骨塞对，并在静载荷（0.15-1.0 MPa）下和不静载荷下进行核磁共振测量。无负荷软骨的T_1在关节面以下最大，向关节深部逐渐减小。同一软骨的T_2在关节表面或关节表面以下处最大，向中间区迅速下降，但在最深区再次增加。最深层T_2的增加在负重区比非负重区更为显著。这些T_1和T_2的层依赖性差异可以解释MR图像中关节软骨的层状外观。在静载荷作用下，过渡区（从关节表面正下方到中间区）T_1的降低是显著的。由于T_1与含水量呈正相关，T_1的减小可能表明过渡区水分损失最大。这些结果表明，过渡区可能会减弱关节内的机械应力，并且软骨中表达的水可以大大促进关节的润滑。

The structural characteristics of articular cartilage were analyzed usnig ^1H-longitudinal (T_1) and transverse (T_2) relaxation times as measured by fast-inversion-recovery and multi-spin-echo magnetic resonance imaging(MRI). Pairs of cartilage-bone plugs from weight bearing and non-weight bearing regions were dissected from 15 medial femoral condyles and were subjected to NMR measurements with and without static loads (0.15-1.0 MPa). The T_1 of the cartilage with no load showed a maximum value just beneath the articular surface and this value decreased gradually towards the deeper zones. The T_2 of the same cartilage showed a maximum value at or just beneath the articular surface which decreased rapidly towards the intermediate zone yet increased again in the deepest zone. The increase of T_2 in the deepest zone was more greatly pronounced in the weight bearing region than in the non-weight bearing region. These layer-dependent differences in the T_1 and T_2 could account for the laminar appearance of the articular cartilage in the MR images. Under static loads, the decrease of T_1 in the transitional zone (from just beneath the articular surface to the intermidiate zone) was significant. Because the T_1 has a positive correlation with the water content, this decrease of T_1 might signify that the largest water loss occurs in the transitional zone. These results suggest that the transitional zone might be attenuating the mechanical stress in the joint, and the expressed water from the cartilage could substantially contribute to the lubrication of the joint.