Alhadlaq Hisham A, Xia Yang
Department of Physics and Center for Biomedical Research, Oakland University, Rochester, MI 48309, USA.
Osteoarthritis Cartilage. 2004 Nov;12(11):887-94. doi: 10.1016/j.joca.2004.07.006.
To detect structural adaptations of collagen fiber matrix in compressed articular cartilage in individual sub-tissue zones by microscopic magnetic resonance imaging (microMRI) at 23 microm in-depth resolution.
Each of the six beagle humeral cartilage specimens was placed in a specially built nonmetallic compression device inside an in-situ rotation device, and was imaged four times at 7T: without and during static compression, and at two orientations: 0 degrees and 55 degrees . Proton intensity images and quantitative T(2) maps were constructed and analyzed.
Upon compression at 55 degrees (the magic angle), rather than appearing homogenous, T(2)-weighted intensity images of cartilage showed a distinct laminar appearance and the T(2) profiles exhibited two distinctive peaks. At both 0 degrees and 55 degrees orientations, lower values of T(2) were observed in compressed tissue. A significant correlation was established between changes in tissue T(2) at 55 degrees and a thickness reduction due to compression. At a mean of 20% strain value, modifications in cartilage structure were studied at each histological zone. We found that the percentage of superficial zone was significantly doubled, the percentage of radial zone was significantly decreased by 10%, and no significant change in the transitional zone.
External loading can induce a new kind of laminar appearance at the magic angle. microMRI T(2) anisotropy can be used to analyze the zone-specific alterations in collagen fibril organization in articular cartilage in response to mechanical compression.
通过深度分辨率为23微米的微观磁共振成像（microMRI）检测单个亚组织区域中受压关节软骨胶原纤维基质的结构适应性。
将六只比格犬的肱骨软骨标本分别置于原位旋转装置内特制的非金属压缩装置中，在7T磁场下进行四次成像：分别在无静态压缩、静态压缩过程中成像，且成像方向有两个：0度和55度。构建并分析质子强度图像和定量T(2)图。
在55度（魔角）压缩时，软骨的T(2)加权强度图像并非呈现均匀状态，而是显示出明显的分层外观，且T(2)曲线呈现出两个明显的峰值。在0度和55度方向上，受压组织的T(2)值均较低。在55度时组织T(2)的变化与压缩导致的厚度减小之间建立了显著的相关性。在平均20%应变值下，研究了每个组织学区域软骨结构的变化。我们发现，表层区域的百分比显著增加了一倍，放射状区域的百分比显著降低了10%，而过渡区域无显著变化。
外部加载可在魔角处诱导出一种新的分层外观。microMRI T(2)各向异性可用于分析关节软骨中胶原纤维组织因机械压缩而产生的区域特异性改变。
