Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania, MRI Education Center, Philadelphia, Pennsylvania 19104, USA.
J Magn Reson Imaging. 2011 Feb;33(2):372-81. doi: 10.1002/jmri.22439.
To assess the performance of a 3D fast spin echo (FSE) pulse sequence utilizing out-of-slab cancellation through phase alternation and micro-magnetic resonance imaging (μMRI)-based virtual bone biopsy processing methods to probe the serial reproducibility and sensitivity of structural and mechanical parameters of the distal tibia at 7.0T.
The distal tibia of five healthy subjects was imaged at three timepoints with a 3D FSE sequence at 137 × 137 × 410 μm(3) voxel size. Follow-up images were retrospectively 3D registered to baseline images. Coefficients of variation (CV) and intraclass correlation coefficients (ICCs) for measures of scale and topology of the whole tibial trabecular bone (TB) cross-section as well as finite-element-derived Young's and shear moduli of central cuboidal TB subvolumes (8 × 8 × 5 mm(3) ) were evaluated as measures of reproducibility and reliability. Four additional cubic TB subregions (anterior, medial, lateral, and posterior) of similar dimensions were extracted and analyzed to determine associations between whole cross-section and subregional structural parameters.
The mean signal-to-noise ratio (SNR) over the 15 image acquisitions was 27.5 ± 2.1. Retrospective registration yielded an average common analysis volume of 67% across the three exams per subject. Reproducibility (mean CV = 3.6%; range, 1.5%-5%) and reliability (ICCs, 0.95-0.99) of all parameters permitted parameter-based discrimination of the five subjects in spite of the narrow age range (26-36 years) covered. Parameters characterizing topology were better able to distinguish two individuals who demonstrated similar values for scalar measurements (≈ 34% difference, P < 0.001). Whole-section axial stiffness encompassing the cortex was superior at distinguishing two individuals relative to its central subregional TB counterpart (≈ 8% difference; P < 0.05). Interregion comparisons showed that although all parameters were correlated (mean R(2) = 0.78; range 0.57-0.99), the strongest associations observed were those for the erosion index (mean R(2) = 0.95, P ≤ 0.01).
The reproducibility and structural and mechanical parameter-based discriminative ability achieved in five healthy subjects suggests that 7T-derived μMRI of TB can be applied towards serial patient studies of osteoporosis and may enable earlier detection of disease or treatment-based effects.
评估一种利用相位交替和基于微磁共振成像（μMRI）的虚拟骨活检处理方法进行离体消除的 3D 快速自旋回波（FSE）脉冲序列在 7.0T 下探测胫骨远端结构和力学参数的系列重现性和敏感性的性能。
对 5 名健康受试者的胫骨远端进行成像，使用 3D FSE 序列进行成像，体素大小为 137×137×410μm(3)。对随访图像进行回顾性 3D 配准至基线图像。评估整个胫骨小梁骨（TB）横截面的标度和拓扑测量的变异系数（CV）和组内相关系数（ICC），以及中央立方 TB 子体积（8×8×5mm(3)）的有限元衍生杨氏和剪切模量，作为重现性和可靠性的测量指标。提取了另外四个具有相似尺寸的立方 TB 子区域（前、内、外和后）并进行了分析，以确定整个横截面和子区域结构参数之间的关系。
15 次图像采集的平均信噪比（SNR）为 27.5±2.1。每个受试者的三次检查平均共有 67%的公共分析体积。尽管所涵盖的年龄范围较窄（26-36 岁），但所有参数的重现性（平均 CV=3.6%；范围 1.5%-5%）和可靠性（ICC，0.95-0.99）都允许基于参数对五名受试者进行区分。表征拓扑的参数能够更好地区分两个具有相似标量测量值的个体（差异约为 34%，P<0.001）。包含皮质的整个截面轴向刚度在区分两个个体方面优于其中央 TB 子区域的对应刚度（差异约为 8%；P<0.05）。区域间比较表明，尽管所有参数均相关（平均 R(2)=0.78；范围 0.57-0.99），但观察到的最强相关性是侵蚀指数（平均 R(2)=0.95，P≤0.01）。
在 5 名健康受试者中实现的重现性以及结构和力学参数的区分能力表明，TB 的 7T 衍生μMRI 可应用于骨质疏松症的患者系列研究，并可能有助于更早地发现疾病或治疗效果。
