NMR Research Unit, Department of Neuroinflammation, Queen Square MS Centre, UCL Institute of Neurology, University College London, UK.
NMR Research Unit, Department of Neuroinflammation, Queen Square MS Centre, UCL Institute of Neurology, University College London, UK.
Neuroimage. 2015 May 1;111:590-601. doi: 10.1016/j.neuroimage.2015.01.045. Epub 2015 Jan 31.
Here we present the application of neurite orientation dispersion and density imaging (NODDI) to the healthy spinal cord in vivo. NODDI provides maps such as the intra-neurite tissue volume fraction (vin), the orientation dispersion index (ODI) and the isotropic volume fraction (viso), and here we investigate their potential for spinal cord imaging. We scanned five healthy volunteers, four of whom twice, on a 3T MRI system with a ZOOM-EPI sequence. In accordance to the published NODDI protocol, multiple b-shells were acquired at cervical level and both NODDI and diffusion tensor imaging (DTI) metrics were obtained and analysed to: i) characterise differences in grey and white matter (GM/WM); ii) assess the scan-rescan reproducibility of NODDI; iii) investigate the relationship between NODDI and DTI; and iv) compare the quality of fit of NODDI and DTI. Our results demonstrated that: i) anatomical features can be identified in NODDI maps, such as clear contrast between GM and WM in ODI; ii) the variabilities of vin and ODI are comparable to that of DTI and are driven by biological differences between subjects for ODI, have similar contribution from measurement errors and biological variation for vin, whereas viso shows higher variability, driven by measurement errors; iii) NODDI identifies potential sources contributing to DTI indices, as in the brain; and iv) NODDI outperforms DTI in terms of quality of fit. In conclusion, this work shows that NODDI is a useful model for in vivo diffusion MRI of the spinal cord, providing metrics closely related to tissue microstructure, in line with findings in the brain.
在这里，我们介绍了神经突方向分散和密度成像（NODDI）在活体健康脊髓中的应用。NODDI 提供了像内神经突组织分数（vin）、方向分散指数（ODI）和各向同性分数（viso）这样的图谱，在这里我们研究了它们在脊髓成像中的潜力。我们在 3T MRI 系统上用 ZOOM-EPI 序列对 5 名健康志愿者进行了扫描，其中 4 名志愿者进行了两次扫描。根据已发表的 NODDI 方案，在颈椎水平采集了多个 b 壳，获得了 NODDI 和扩散张量成像（DTI）指标，并对其进行了分析：i）描述灰质和白质（GM/WM）之间的差异；ii）评估 NODDI 的扫描可重复性；iii）研究 NODDI 和 DTI 之间的关系；iv）比较 NODDI 和 DTI 的拟合质量。我们的结果表明：i）在 NODDI 图谱中可以识别出解剖特征，如 ODI 中 GM 和 WM 之间的明显对比；ii）vin 和 ODI 的变异性与 DTI 相当，并且是由 ODI 受试者之间的生物学差异驱动的，vin 的变异性受测量误差和生物学变异的影响相似，而 viso 的变异性更高，是由测量误差驱动的；iii）NODDI 确定了可能导致 DTI 指数变化的潜在来源，如在大脑中；iv）NODDI 在拟合质量方面优于 DTI。总之，这项工作表明，NODDI 是一种有用的脊髓活体扩散 MRI 模型，提供了与组织微观结构密切相关的指标，与大脑中的发现一致。
