Characterization of anisotropic T2W signals from human knee femoral cartilage: The magic angle effect on a spherical surface.
Characterization of anisotropic T2W signals from human knee femoral cartilage: The magic angle effect on a spherical surface.
复制标题
人膝股骨软骨各向异性 T2W 信号的表征：球面上的魔角效应。
DOI：
10.1002/nbm.4535
复制
发表时间：
2021
影响因子：
2.9
通讯作者：
Pang,Yuxi
中科院分区：
文献类型：
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作者：
Pang,Yuxi
本研究的目的是提出一种广义魔角效应 (gMAE) 函数，用于表征临床研究中具有球形表面的人类膝关节股骨软骨的各向异性 T2W 信号。 gMAE 模型函数 f(α,ε) 是针对软骨中方向依赖性 (ε) 横向 T2（即 1/R2）松弛而制定的，假设胶原纤维呈轴对称分布 (α)。 T2W 矢状图像是在 3 T 下在成年志愿者的健康膝盖上获取的，并且从成角度和径向分段的股骨软骨中提取基于 ROI 的平均信号 S(ε)。与深层 (DZ,α= 0°) 和浅层 (SZ,α= 90°) 区域的标准 MAE (sMAE) 函数相比，S(ε) 拟合了 R2 方向相关函数 f(α,ε) 的一般形式，包括各向同性 R2 贡献（内部参考 [REF]）。拟合优度通过均方根偏差（RMSD）进行评估。 AnF 检验和配对检验分别用于评估观察到的方差和均值之间的显着差异，统计显着性设置小于 0.05。作为具有变化动态范围的对称方向依赖函数，所提出的 gMAE 模型优于之前的 sMAE 函数，表现为 DZ 中的 RMSD 显着降低（0.239 ± 0.122 与 0.267 ± 0.097，p =.014）和 SZ 中（0.183 ± 0.081）与 0.254 ±0.085，p <.001)。 DZ 的拟合平均角度α（38.5 ± 34.6° vs. 45.1±±30.1°，p <.43）和 REF（5.092 ± 0.369 vs. 5.305± 0.440，p <.001）均小于 SZ，与报道的胶原纤维微结构配置和关节软骨中非结合水对 R2 的贡献一致。总之，提出并论证了魔角效应函数的一般形式，以便在临床研究中更好地表征 3 T 下人类膝关节股骨软骨的各向异性 T2W 信号。
The aim of the current study was to propose a generalized magic angle effect (gMAE) function for characterizing anisotropic T2W signals of human knee femoral cartilage with a spherical surface in clinical studies. A gMAE model functionf(α,ε) was formulated for an orientation‐dependent (ε) transverseT2(i.e., 1/R2) relaxation in cartilage assuming an axially symmetric distribution (α) of collagen fibers. T2W sagittal images were acquired on an adult volunteer's healthy knee at 3 T, and ROI‐based average signalsS(ε) were extracted from angularly and radially segmented femoral cartilage. Compared with the standard MAE (sMAE) functions in the deep (DZ,α= 0°) and in the superficial (SZ,α= 90°) zones, a general form ofR2orientation‐dependent functionf(α,ε) was fitted toS(ε), including an isotropicR2contribution (internal reference [REF]). Goodness of fit was evaluated by root‐mean‐square deviations (RMSDs). AnF‐test and a pairedt‐test were respectively used to assess significant differences between the observed variances and means, with statistical significance set topless than .05. As a symmetric orientation‐dependence function with a varying dynamic range, the proposed gMAE model outperformed the previous sMAE functions manifested by significantly reduced RMSDs in the DZ (0.239 ± 0.122 vs. 0.267 ± 0.097,p =.014) and in the SZ (0.183 ± 0.081 vs. 0.254 ± 0.085,p <.001). The fitted average angleα(38.5 ± 34.6° vs. 45.1 ± 30.1°,p <.43) and REF (5.092 ± 0.369 vs. 5.305 ± 0.440,p <.001) were smaller in the DZ than those in SZ, in good agreement with the reported collagen fibril microstructural configurations and the nonbound water contribution toR2in articular cartilage. In conclusion, a general form of the magic angle effect function was proposed and demonstrated for better characterizing anisotropic T2W signals from human knee femoral cartilage at 3 T in clinical studies.