Division of MRI Research, Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, MA, USA.
Division of MRI Research, Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, MA, USA.
Neuroimage. 2021 Jan 15;225:117442. doi: 10.1016/j.neuroimage.2020.117442. Epub 2020 Oct 9.
Myelin specific imaging techniques to characterize white matter in demyelinating diseases such as multiple sclerosis (MS) have become an area of increasing focus. Gray matter myelination is an important marker of cortical microstructure, and its impairment is relevant in progressive MS. However, its assessment is challenging due to its thin layers. While myelin water imaging and ultra-short TE imaging have not yet been implemented to assess cortical myeloarchitecture, magnetization transfer (MT) shows promise. A recent development of the MT technique, ihMT, has demonstrated greater myelin sensitivity/specificity. Here we implemented a 3D ihMT acquisition and analysis to characterize cortical gray matter myeloarchitecture.
20 young healthy volunteers were imaged with a 3D ihMTRAGE sequence and quantitative metrics of ihMT (ihMTsat), and dual frequency-offset MT (dual MTsat) were calculated. Cortical surface-based analysis of ihMTsat and dual MTsat were performed and compared. We also compared the cortical ihMTsat map to a cortical surface-based map of T-weighted images (Tw), defined as a proxy of myelin content.
Cortical ihMTsat and dual MTsat maps were in qualitative agreement with previous work and the cortical Tw map, showing higher values in primary cortices and lower values in the insula. IhMTsat and dual MTsat were significantly correlated but with important regional differences. The ratio ihMTsat/dual MTsat highlighted higher ihMTsat values in the primary cortices and sulci.
ihMTsat, a quantitative metric of ihMT, can be reliably measured in cortical gray matter and shows unique contrast between cortical regions.
用于表征脱髓鞘疾病（如多发性硬化症[MS]）中的白质的髓鞘特异性成像技术已成为日益关注的领域。灰质髓鞘形成是皮质微观结构的重要标志物，在进展性 MS 中其损伤是相关的。然而，由于其薄层，其评估具有挑战性。虽然尚未采用髓水成像和超短 TE 成像来评估皮质髓鞘结构，但磁化转移（MT）显示出前景。MT 技术的最新发展，ihMT，已证明具有更高的髓鞘敏感性/特异性。在这里，我们实施了 3D ihMT 采集和分析，以表征皮质灰质髓鞘结构。
对 20 名年轻健康志愿者进行了 3D ihMTRAGE 序列成像，并计算了 ihMT 的定量指标（ihMTsat）和双频偏移 MT（dual MTsat）。对 ihMTsat 和 dual MTsat 的皮质表面分析进行了比较。我们还将皮质 ihMTsat 图与皮质表面的 T 加权图像（Tw）图进行了比较，Tw 图被定义为髓鞘含量的替代物。
皮质 ihMTsat 和 dual MTsat 图与先前的工作和皮质 Tw 图在定性上一致，在初级皮质中表现出较高的值，在脑岛中表现出较低的值。ihMTsat 和 dual MTsat 显著相关，但具有重要的区域差异。ihMTsat/dual MTsat 的比值突出了初级皮质和脑回中更高的 ihMTsat 值。
ihMT 的定量指标 ihMTsat 可在皮质灰质中可靠测量，并显示出皮质区域之间的独特对比。
