Objective

Magnetization EXchange (MEX) sequence measures a signal linearly dependent on the myelin proton fraction by selective suppression of water magnetization and a recovery period. Varying the recovery period enables extraction of the percentile fraction of myelin bound protons. We aim to demonstrate the MEX sequence sensitivity to the fraction of protons associated with myelin in mice brain, in vivo.

Methods

The cuprizone mouse model was used to manipulate the myelin content. Mice fed cuprizone (n = 15) and normal chow (n = 8) were imaged in vivo using MEX sequence. MR images were segmented into corpus callosum and internal capsule (white matter) and cortical gray matter, and fitted to the recovery equation. Results were analyzed with correlation to MWF and histopathology.

Results

The extracted parameters show significant differences in the corpus callosum between the cuprizone and control groups. The cuprizone group exhibited reduced myelin fraction 26.5% (P < 0.01). The gray matter values were less affected, with 13.5% reduction (P < 0.05); no changes were detected in the internal capsule. Results were validated by MWF scans and good correlation to the histology analysis (R² = 0.685).

Conclusion

The results of this first in vivo implementation of the MEX sequence provide a quantitative measure of demyelination in brain white matter.

中文翻译：

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MEX MRI 对小鼠大脑髓鞘部分的体内实施

客观的

磁化交换 (MEX) 序列通过选择性抑制水磁化和恢复期来测量线性依赖于髓鞘质子分数的信号。改变恢复期可以提取髓磷脂结合质子的百分位数。我们的目标是在体内证明 MEX 序列对与小鼠大脑中髓鞘相关的质子分数的敏感性。

方法

Cuprizone 小鼠模型用于操纵髓磷脂含量。使用 MEX 序列对喂食铜酮 ( n  = 15) 和正常食物 ( n = 8) 的小鼠 进行体内成像。MR图像被分割为胼胝体和内囊（白质）和皮质灰质，并拟合恢复方程。分析结果与 MWF 和组织病理学的相关性。

结果

提取的参数显示铜酮组和对照组之间胼胝体的显着差异。铜宗组的髓磷脂分数降低 26.5% ( P  < 0.01)。灰质值受影响较小，减少13.5%（P  < 0.05）；内囊未检测到变化。结果通过 MWF 扫描得到验证，并与组织学分析具有良好的相关性 ( R ²  = 0.685)。

结论

MEX 序列的首次体内实施的结果提供了脑白质脱髓鞘的定量测量。