Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA.
Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA.
Neuroimage. 2019 Oct 15;200:191-198. doi: 10.1016/j.neuroimage.2019.06.049. Epub 2019 Jun 21.
The locus coeruleus (LC) is the major origin of norepinephrine in the central nervous system, and is subject to age-related and neurodegenerative changes, especially in disorders such as Parkinson's disease and Alzheimer's disease. Previous studies have shown that neuromelanin (NM)-sensitive MRI can be used to visualize the LC, and it is hypothesized that magnetization transfer (MT) effects are the primary source of LC contrast. The aim of this study was to characterize the MT effects in LC imaging by applying high spatial resolution quantitative MT (qMT) imaging to create parametric maps of the macromolecular content of the LC and surrounding tissues. Healthy volunteers (n = 26; sex = 17 F/9M; age = 41.0 ± 19.1 years) underwent brain MRI on a 3.0 T scanner. qMT data were acquired using a 3D MT-prepared spoiled gradient echo sequence. A traditional NM scan consisting of a T-weighted turbo spin echo sequence with MT preparation was also acquired. The pool-size ratio (PSR) was estimated for each voxel using a single-point qMT approach. The LC was semi-automatically segmented on the MT-weighted images. The MT-weighted images provided higher contrast-ratio between the LC and surrounding pontine tegmentum (PT) (0.215 ± 0.031) than the reference images without MT-preparation (-0.005 ± 0.026) and the traditional NM images (0.138 ± 0.044). The PSR maps showed significant differences between the LC (0.090 ± 0.009) and PT (0.188 ± 0.025). The largest difference between the PSR values in the LC and PT was observed in the central slices, which also correspond to those with the highest contrast-ratio. These results highlight the role of MT in generating NM-related contrast in the LC, and should serve as a foundation for future studies aiming to quantify pathological changes in the LC and surrounding structures in vivo.
蓝斑（LC）是中枢神经系统去甲肾上腺素的主要来源，并且会随着年龄的增长和神经退行性变化而发生变化，尤其是在帕金森病和阿尔茨海默病等疾病中。先前的研究表明，神经黑色素（NM）敏感 MRI 可用于可视化 LC，并且假设磁化传递（MT）效应是 LC 对比的主要来源。本研究的目的是通过应用高空间分辨率定量 MT（qMT）成像来对 LC 成像中的 MT 效应进行特征描述，从而创建 LC 和周围组织的大分子含量的参数图。健康志愿者（n=26；性别=17 女/9 男；年龄=41.0±19.1 岁）在 3.0T 扫描仪上进行脑部 MRI 检查。使用 3D MT 准备的扰相梯度回波序列采集 qMT 数据。还采集了由具有 MT 准备的 T 加权涡轮自旋回波序列组成的传统 NM 扫描。使用单点 qMT 方法估计每个体素的池大小比（PSR）。在 MT 加权图像上半自动分割 LC。MT 加权图像提供了 LC 与周围脑桥被盖（PT）之间更高的对比度比（0.215±0.031），而没有 MT 准备的参考图像（-0.005±0.026）和传统 NM 图像（0.138±0.044）。PSR 图显示 LC（0.090±0.009）和 PT（0.188±0.025）之间的 PSR 图有显著差异。LC 和 PT 之间 PSR 值的最大差异出现在中心切片中，这也与最高对比度相对应。这些结果强调了 MT 在产生 LC 中与 NM 相关的对比中的作用，并且应该作为未来旨在在体内定量 LC 和周围结构的病理变化的研究的基础。
