From the Aix-Marseille University, CNRS, Centre de Résonance Magnétique Biologique et Médicale (CRMBM), UMR 7339, Faculté de Médecine la Timone, 27 Boulevard Jean Moulin, 13385 Marseille, France (A.F., A.C.O., A.L.T., C.V., M.G., J.G., P.B., D.B.); APHM, Hôpital Universitaire Timone, CEMEREM, Pôle Imagerie Médicale, Marseille, France (M.G.); Institut NeuroMyoGène, Université Claude Bernard Lyon 1, INSERM U1217, CNRS 5310, Villeurbanne, France (J.G.); and Siemens Healthcare, Erlangen, Germany (T.F.).
Radiology. 2018 May;287(2):592-607. doi: 10.1148/radiol.2017171330. Epub 2018 Jan 30.
Purpose To demonstrate the reproducibility of the diffusion properties and three-dimensional structural organization measurements of the lower leg muscles by using diffusion-tensor imaging (DTI) assessed with ultra-high-field-strength (7.0-T) magnetic resonance (MR) imaging and tractography of skeletal muscle fibers. On the basis of robust statistical mapping analyses, this study also aimed at determining the sensitivity of the measurements to sex difference and intramuscular variability. Materials and Methods All examinations were performed with ethical review board approval; written informed consent was obtained from all volunteers. Reproducibility of diffusion tensor indexes assessment including eigenvalues, mean diffusivity, and fractional anisotropy (FA) as well as muscle volume and architecture (ie, fiber length and pennation angle) were characterized in lower leg muscles (n = 8). Intramuscular variability and sex differences were characterized in young healthy men and women (n = 10 in each group). Student t test, statistical parametric mapping, correlation coefficients (Spearman rho and Pearson product-moment) and coefficient of variation (CV) were used for statistical data analysis. Results High reproducibility of measurements (mean CV ± standard deviation, 4.6% ± 3.8) was determined in diffusion properties and architectural parameters. Significant sex differences were detected in FA (4.2% in women for the entire lower leg; P = .001) and muscle volume (21.7% in men for the entire lower leg; P = .008), whereas architecture parameters were almost identical across sex. Additional differences were found independently of sex in diffusion properties and architecture along several muscles of the lower leg. Conclusion The high-spatial-resolution DTI assessed with 7.0-T MR imaging allows a reproducible assessment of structural organization of superficial and deep muscles, giving indirect information on muscle function. RSNA, 2018 Online supplemental material is available for this article.
目的 利用超高场强（7.0-T）磁共振成像（MR）弥散张量成像（DTI）评估下肢肌肉的弥散特性和三维结构组织测量，并证明其可重复性，同时对骨骼肌纤维进行示踪。在此基础上，稳健的统计映射分析还旨在确定这些测量对性别差异和肌内变异性的敏感性。
材料与方法 所有检查均经伦理审查委员会批准；所有志愿者均书面签署知情同意书。对 8 例志愿者的下肢肌肉进行弥散张量指数评估（包括本征值、平均弥散度和各向异性分数（FA）以及肌肉体积和结构（即纤维长度和肌纤维角度））的重复性研究。在年轻健康的男性和女性志愿者中（每组 10 例），对肌内变异性和性别差异进行了研究。采用 Student t 检验、统计参数映射、相关系数（Spearman rho 和 Pearson 积矩）和变异系数（CV）进行统计学数据分析。
结果 测量的重复性高（弥散特性和结构参数的平均 CV ± 标准差为 4.6%±3.8）。FA（女性整个下肢的差异为 4.2%；P =.001）和肌肉体积（男性整个下肢的差异为 21.7%；P =.008）存在显著的性别差异，而结构参数在性别间几乎相同。在下肢的几处肌肉中，除性别外，还发现了弥散特性和结构参数的其他差异。
结论 7.0-T MR 成像的高空间分辨率 DTI 可重复性评估下肢浅表和深部肌肉的结构组织，为肌肉功能提供间接信息。
RSNA，2018 在线补充材料可从本文获得。
