Palombarini Marcella, Gombia Mirko, Fantazzini Paola, Giardino Roberto, Giavaresi Gianluca, Parrilli Annapaola, Vittur Franco, Guillot Genevieve
Medical Physics Department, Bellaria Hospital, Bologna, Italy.
J Magn Reson Imaging. 2009 Oct;30(4):825-33. doi: 10.1002/jmri.21902.
To analyze the 3D microarchitecture of rat lumbar vertebrae by micro-magnetic resonance imaging (micro-MRI).
micro-MR images (20 x 20 x 20 microm(3) apparent voxel size) were acquired with a three-dimensional spin-echo pulse sequence on four lumbar vertebrae of two rats. Apparent microarchitectural parameters like trabecular bone fraction (BV/TV), specific bone surface (BS/TV), mean intercept length (MIL), and Euler number per unit volume (Euler density, E(V)) were calculated using a novel semiquantitative variable threshold segmentation technique. The threshold value T was obtained as a point of minimum or maximum of the function E(V) = E(V)(T).
Quantitative 3D analysis of micro-MRI images revealed a higher connectivity in the peripheral regions (E(V) = -570 +/- 70 mm(-3)) than in the central regions (E(V) = -130 +/- 50 mm(-3)) of the analyzed rat lumbar vertebrae. Smaller intertrabecular cavities and larger bone volume fractions were observed in peripheral regions as compared to central ones (MIL = 0.18 +/- 0.01 mm and 0.26 +/- 0.01 mm; BV/TV = 34 +/- 3% and 29 +/- 3%, respectively). The quantitative 3D study of MIL showed a structural anisotropy of the trabeculae along the longitudinal axis seen on the images. The inhomogeneity of the bone architecture was validated by micro-computed tomography (micro-CT) images at the same spatial resolution.
3D high-field micro-MRI is a suitable technique for the assessment of bone quality in experimental animal models.
通过显微磁共振成像（micro-MRI）分析大鼠腰椎的三维微观结构。
使用三维自旋回波脉冲序列对两只大鼠的四个腰椎获取显微磁共振图像（表观体素大小为20×20×20立方微米）。使用一种新型的半定量可变阈值分割技术计算表观微观结构参数，如骨小梁骨分数（BV/TV）、比骨表面积（BS/TV）、平均截距长度（MIL）和单位体积欧拉数（欧拉密度，E(V)）。阈值T作为函数E(V)=E(V)(T)的最小值或最大值点获得。
对显微磁共振图像的定量三维分析显示，所分析的大鼠腰椎外周区域（E(V)= -570±70毫米-3）的连通性高于中央区域（E(V)= -130±50毫米-3）。与中央区域相比，外周区域观察到小梁间腔较小且骨体积分数较大（MIL分别为0.18±0.01毫米和0.26±0.01毫米；BV/TV分别为34±3%和29±3%）。对MIL的定量三维研究显示了图像上沿纵轴的小梁结构各向异性。在相同空间分辨率下通过显微计算机断层扫描（micro-CT）图像验证了骨结构的不均匀性。
三维高场显微磁共振成像（3D high-field micro-MRI）是评估实验动物模型骨质量的合适技术。
