The primary lesion arising from the initial insult after traumatic brain injury (TBI) triggers a cascade of secondary tissue damage, which may also progress to connected brain areas in the chronic phase. The aim of this study was, therefore, to investigate variations in the susceptibility distribution related to these secondary tissue changes in a rat model after severe lateral fluid percussion injury. We compared quantitative susceptibility mapping (QSM) and R₂* measurements with histological analyses in white and grey matter areas outside the primary lesion but connected to the lesion site. We demonstrate that susceptibility variations in white and grey matter areas could be attributed to reduction in myelin, accumulation of iron and calcium, and gliosis. QSM showed quantitative changes attributed to secondary damage in areas located rostral to the lesion site that appeared normal in R₂* maps. However, combination of QSM and R₂* was informative in disentangling the underlying tissue changes such as iron accumulation, demyelination, or calcifications. Therefore, combining QSM with R₂* measurement can provide a more detailed assessment of tissue changes and may pave the way for improved diagnosis of TBI, and several other complex neurodegenerative diseases.

中文翻译：

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外伤性脑损伤后大鼠脑的定量磁敏感图

外伤性脑损伤 (TBI) 后最初的损伤引起的原发性损伤引发了继发性组织损伤的级联反应，在慢性期也可能进展到连接的大脑区域。因此，本研究的目的是调查与严重侧向流体冲击损伤后大鼠模型中这些继发性组织变化相关的易感性分布的变化。我们比较了定量磁化率映射 (QSM) 和R ₂* 在原发病灶外但与病灶部位相连的白质和灰质区域进行组织学分析测量。我们证明白质和灰质区域的易感性变化可归因于髓鞘减少、铁和钙的积累以及神经胶质增生。QSM 显示出归因于损伤部位嘴侧区域的继发性损伤的定量变化，在R ₂ * 图中显示正常。然而，QSM 和R ₂ * 的组合在解开潜在的组织变化（如铁积累、脱髓鞘或钙化）方面提供了丰富的信息。因此，将 QSM 与R ₂* 测量可以提供对组织变化的更详细评估，并可能为改进 TBI 和其他几种复杂神经退行性疾病的诊断铺平道路。