7 T 下脂肪对基于 NOE 的磁共振对比成像的影响

核 Overhauser 增强(NOE)效应在高场下的化学交换饱和转移中会造成 Z 谱高场位置的负背景信号，有望成为一种新的磁共振成像(MRI)对比机制．然而，研究指出， NOE信号的发生区域与主要的脂肪信号的频率位置有重叠，因此 MRI 中观察到的 NOE 信号有可能混合了脂肪信号．该文通过鸡蛋的模型实验，初步分析了脂肪含量较高的组织内脂肪信号对 NOE 效应的影响，并通过健康大鼠鼠脑及颅内肿瘤大鼠鼠脑实验，分析了脂肪对脑部 NOE 对比成像及基于 NOE 对比成像的疾病诊断的影响．结果表明，脂肪含量较高的组织内脂肪信号会引起伪 NOE 效应，并影响 NOE对比图像的准确性．

Effects of Lipids Signals on Nuclear Overhauser Enhancement Contrast Imaging at 7 T

When performingchemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) on biological samples at high fields, nuclear Overhauser enhancement (NOE) effects may produce negative signals on the Z-spectra. The NOE-related signal intensity changes have the potential to become a new contrast mechanism. However, the presence of lipids signals within the same chemical shift range may affect the observation of true NOE effect-related signal changes. In this work, we first analyzed the influence of lipid signals on the NOE effects in tissues abundant in lipid via experiments on eggs. Similar experiments were then carried out on healthy rats and rats with brain tumors. The results showed that the presence of large lipid signals could cause pseudo NOE effects and degrade the accuracy of NOE contrast imaging.