Spinal cord injuries (SCIs) are a leading cause of disability and can severely impact the quality of life. However, to date, the processes of spontaneous repair of damaged spinal cord remain incompletely understood, partly due to a lack of appropriate longitudinal tracking methods. Noninvasive, multiparametric magnetic resonance imaging (MRI) provides potential biomarkers for the comprehensive evaluation of spontaneous repair after SCI. In this study in rats, a clinically relevant contusion injury was introduced at the lumbar level that impairs both hindlimb motor and sensory functions. Quantitative MRI measurements were acquired at baseline and serially post-SCI for up to 2 wk. The progressions of injury and spontaneous recovery in both white and gray matter were tracked longitudinally using pool-size ratio (PSR) measurements derived from quantitative magnetization transfer (qMT) methods, measurements of water diffusion parameters using diffusion tensor imaging (DTI) and intrasegment functional connectivity derived from resting state functional MRI. Changes in these quantitative imaging measurements were correlated with behavioral readouts. We found (a) a progressive decrease in PSR values within 2 wk post-SCI, indicating a progressive demyelination at the center of the injury that was validated with histological staining, (b) PSR correlated closely with fractional anisotropy and transverse relaxation of free water, but did not show significant correlations with behavioral recovery, and (c) preliminary evidence that SCI induced a decrease in functional connectivity between dorsal horns below the injury site at 24 h. Findings from this study not only confirm the value of qMT and DTI methods for assessing the myelination state of injured spinal cord but indicate that they may also have further implications on whether therapies targeted towards remyelination may be appropriate. Additionally, a better understanding of changes after SCI provides valuable information to guide and assess interventions.

中文翻译：

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行为评估和扩散，定量磁化转移和功能磁共振成像对脊髓损伤后恢复的纵向评估。

脊髓损伤（SCI）是导致残疾的主要原因，并且可能严重影响生活质量。然而，迄今为止，对受损脊髓的自发修复过程仍未完全了解，部分原因是缺乏适当的纵向追踪方法。无创多参数磁共振成像（MRI）为SCI后的自发修复提供了全面评估的潜在生物标志物。在大鼠的这项研究中，在腰椎水平引入了临床相关的挫伤性损伤，损害了后肢运动和感觉功能。在基线和SCI后连续2 wk进行定量MRI测量。使用从定量磁化传递（qMT）方法获得的池尺寸比（PSR）测量，使用扩散张量成像（DTI）和段内功能测量水扩散参数的方法纵向跟踪白和灰质中损伤和自发恢复的进程连通性源自静息状态功能MRI。这些定量成像测量的变化与行为读数相关。我们发现（a）SCI后2周内PSR值逐渐降低，表明在损伤中心逐渐进行了脱髓鞘反应，这已通过组织学染色进行了验证；（b）PSR与分数各向异性和自由水的横向松弛密切相关，但与行为恢复没有显着相关性，（c）初步证据表明SCI在24 h损伤部位下方的背角之间的功能连通性降低。这项研究的发现不仅证实了qMT和DTI方法对评估脊髓损伤的髓鞘状态的价值，而且表明它们还可能对针对髓鞘再生的疗法是否合适产生进一步的影响。此外，对SCI之后的变化的更好理解为指导和评估干预措施提供了有价值的信息。这项研究的发现不仅证实了qMT和DTI方法对评估脊髓损伤的髓鞘状态的价值，而且表明它们还可能对针对髓鞘再生的疗法是否合适产生进一步的影响。此外，对SCI之后的变化的更好理解为指导和评估干预措施提供了有价值的信息。这项研究的发现不仅证实了qMT和DTI方法对评估脊髓损伤的髓鞘状态的价值，而且表明它们还可能对针对髓鞘再生的疗法是否合适产生进一步的影响。此外，对SCI之后的变化的更好理解为指导和评估干预措施提供了有价值的信息。