Department of Medical Physics and Engineering, Division of Health Sciences, Osaka University Graduate School of Medicine, Suita, Osaka 560-0871, Japan; Department of Biomedical Imaging, National Cardiovascular and Cerebral Research Center, Suita, Osaka 565-8565, Japan.
Department of Medical Physics and Engineering, Division of Health Sciences, Osaka University Graduate School of Medicine, Suita, Osaka 560-0871, Japan; Department of Biomedical Imaging, National Cardiovascular and Cerebral Research Center, Suita, Osaka 565-8565, Japan.
Magn Reson Imaging. 2019 Oct;62:214-219. doi: 10.1016/j.mri.2019.07.013. Epub 2019 Jul 17.
To evaluate the utility of neurite orientation dispersion and density imaging (NODDI) for longitudinally assessing neonatal hypoxic-ischemic (HI) encephalopathy severity with 7.0 T magnetic resonance imaging.
Thirteen 8-day-old Wistar rats underwent unilateral ligation of the left common carotid artery followed by mild (1 h; n = 6) or severe (2 h; n = 7) hypoxic exposure (8% O, 34 °C). Diffusion-weighted, T-weighted (TW), and flow-sensitive alternating inversion recovery images were obtained with a horizontal 7.0 T scanner at 1, 24, 72, and 168 h after HI insult. The fractional anisotropy (FA), apparent diffusion coefficient (ADC), intracellular volume fraction (ICVF), isotropic volume fraction (ISO), orientation dispersion index (ODI), and cerebral blood flow (CBF) values were calculated for each group (mild and severe) at each time point (1, 24, 72, and 168 h). ICVF, ISO, and ODI were the NODDI parameters.
Left hemisphere brain damage was identified as slight hyperintensity on TW images after 1 h in both groups. In the severe group only, the signal hyperintensity increased time-dependently over 168 h. The ADC and CBF were not significantly different between the groups within any region. The ICVF and ODI were significantly higher in the severe vs. mild group at various points between 1 and 168 h (cortex, striatum, or white matter), whereas the FA was significantly higher in the mild vs. severe group at 168 h (cortex and white matter). The ISO was higher in the severe vs. mild group at 72 h (striatum) and 168 h (all regions), while the ISO was significantly higher in the mild vs. severe group at 24 h (all regions).
Here, ODI, a NODDI metric, identified early differences between mild and severe HI injuries. Our findings support the potential utility of NODDI for determining neonatal HI encephalopathy severity in rats.
评估神经突方向分散与密度成像（NODDI）在 7.0T 磁共振成像中用于纵向评估新生儿缺氧缺血性（HI）脑病严重程度的效用。
13 只 8 天大的 Wistar 大鼠进行左侧颈总动脉结扎，随后进行轻度（1h；n=6）或重度（2h；n=7）缺氧暴露（8%O2，34°C）。在 HI 损伤后 1、24、72 和 168h，使用水平 7.0T 扫描仪获取扩散加权、T 加权（TW）和血流敏感交替反转恢复图像。在每个时间点（1、24、72 和 168h），计算每个组（轻度和重度）的各向异性分数（FA）、表观扩散系数（ADC）、细胞内体积分数（ICVF）、各向同性体积分数（ISO）、方向分散指数（ODI）和脑血流量（CBF）值。ICVF、ISO 和 ODI 是 NODDI 参数。
在两组中，TW 图像上的左半球脑损伤在 1h 时表现为轻度高信号。仅在重度组中，信号高信号随时间呈依赖性增加，持续 168h。在任何区域，两组之间的 ADC 和 CBF 均无显著差异。在 1 至 168h 之间的各个时间点，重度组的 ICVF 和 ODI 均显著高于轻度组（皮质、纹状体或白质），而在 168h 时，轻度组的 FA 显著高于重度组（皮质和白质）。在 72h（纹状体）和 168h（所有区域）时，重度组的 ISO 高于轻度组，而在 24h（所有区域）时，轻度组的 ISO 显著高于重度组。
这里，NODDI 指标 ODI 识别出轻度和重度 HI 损伤之间的早期差异。我们的研究结果支持 NODDI 用于确定大鼠新生儿 HI 脑病严重程度的潜在效用。
