Diffusion tensor imaging (DTI) quantifies microstructural lesion characteristics, but impact of the interval between spinal cord injury (SCI) and examination on imaging characteristics is unclear. Our objective was to investigate the impact of duration of injury on DTI indices in dogs with acute, spontaneous SCI from thoracolumbar intervertebral disc herniation (IVDH) and explore associations with clinical severity. Twenty-six dogs with acute thoracolumbar IVDH of variable severity who underwent DTI were included. Neurological severity was graded using the modified Frankel Score (0–V). Fractional anisotropy (FA) and mean diffusivity (MD) were calculated on regions of interest within and adjacent to the lesion epicenter. Relationships between FA or MD and duration (injury to imaging interval) or neurological severity were determined using regression analysis and Wilcoxon rank sum. Median age was 6.8 years (1–13), median duration was 1.5 days (1–9), and neurological signs ranged from ambulatory paraparesis (MFS II) to paraplegia with absent pain perception (MFS V). Mean FA was 0.61 ± 0.09 cranial to the lesion, 0.57 ± 0.12 at the epicenter and 0.55 ± 0.10 caudally. Mean MD was 1.18 × 10⁻³ ± 0.0002 cranially, 1.09 × 10⁻³ ± 0.0002 at the epicenter, and 1.14 × 10⁻³ ± 0.0002 caudally. Accounting for neurological severity and age, FA caudal to the epicenter decreased with increasing duration of injury (p = 0.02). Lower MD within the lesion epicenter was associated with worse neurological severity (p = 0.01). Duration of injury should be considered when interpreting DTI results in dogs with acute thoracolumbar IVDH. The MD might differentiate injury severity in the acute setting and be worthy of development as an imaging biomarker.

中文翻译：

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急性犬脊髓损伤中损伤持续时间对弥散张量成像的影响。

弥散张量成像 (DTI) 量化微观结构病变特征，但脊髓损伤 (SCI) 和检查之间的间隔对成像特征的影响尚不清楚。我们的目标是研究损伤持续时间对胸腰椎间盘突出症 (IVDH) 急性自发性 SCI 犬 DTI 指数的影响，并探讨其与临床严重程度的关联。包括 26 只接受 DTI 的严重程度不等的急性胸腰椎 IVDH 犬。使用改良的 Frankel 评分 (0-V) 对神经系统严重程度进行分级。计算各向异性分数 (FA) 和平均扩散率 (MD) 在病变中心内和附近的感兴趣区域。使用回归分析和 Wilcoxon 秩和确定 FA 或 MD 与持续时间（成像间隔损伤）或神经系统严重程度之间的关系。中位年龄为 6.8 岁（1-13 岁），中位持续时间为 1.5 天（1-9 天），神经系统体征范围从行走下肢轻瘫 (MFS II) 到痛觉缺失的截瘫 (MFS V)。平均 FA 为 0.61 ± 0.09 颅骨病变，0.57 ± 0.12 在震中和 0.55 ± 0.10 尾部。平均 MD 为 1.18 ×  10 ^-3 ± 0.0002 头颅，1.09  ×  10 ^-3  ± 0.0002 震中，1.14  ×  10 ^-3 ± 0.0002 尾椎。考虑到神经系统的严重程度和年龄，震中尾部 FA 随着损伤持续时间的增加而减少（p  = 0.02）。病变中心内较低的 MD 与更严重的神经系统严重程度相关（p  = 0.01）。在解释患有急性胸腰椎 IVDH 的狗的 DTI 结果时，应考虑损伤的持续时间。MD 可能区分急性情况下的损伤严重程度，值得开发为成像生物标志物。