Abdel-Fahim R, Mistry N, Mougin O, Blazejewska A, Pitiot A, Retkute R, Gowland P, Evangelou N
Division of Clinical Neurology, University of Nottingham, Nottingham, United Kingdom.
Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom.
Mult Scler Relat Disord. 2014 Mar;3(2):258-65. doi: 10.1016/j.msard.2013.10.004. Epub 2013 Oct 19.
Cortical lesions account for a larger proportion of brain demyelination than white matter (WM) lesions. They are often missed on conventional MRI. Recently studies improved the detection of cortical lesions using 7T T2(⁎), 7T MPRAGE and 3T DIR but it seems that we are still able to detect only "the tip of the iceberg". In this study we report for the first time the systematic use of high resolution MTR in MS and compare MTR lesion detection with 7T MPRAGE, 7T T2(⁎) and 3T 3D DIR.
We report the use of high resolution, fast, magnetisation transfer imaging (MTI) at 7T in MS focusing on the detection of cortical lesions.
Eighteen patients with MS were scanned (Expanded Disability Status Scale score: 3.0, mean age: 48 years, mean disease duration: 7.25 years). The scans were compared to nine healthy control subjects (mean age 36.5 years).
We acquired 7T MPRAGE images, 7T MTR maps, 7T T2(⁎)and 3T 3D DIR. The WM was segmented from the MPRAGE and removed to obtain only the cortical grey matter ribbon (cGMR) mask. The mask was then applied to the different modalities (MPRAGE, MTR, DIR, T2(⁎)w) previously registered onto the MPRAGE volume. The analysis of the cGMR was performed by two observers blinded to the disease state.
In patients with MS 365 lesions in total were detected with 7T MTR (mean 20.28 lesions per patient), 289 lesions were detected with 7T MPRAGE (mean 16.06 lesions) and 231 lesions were detected with 7T T2(⁎) (mean 12.83 lesions). In the 8 MS subjects who had 3T 3D DIR acquired on the same day, a total of 136 lesions (mean 17 lesions per patient) were detected as opposed to 171 lesions with 7T MTR, 147 lesions were detected with 7T MPRAGE and 126 lesions with 7T T2(⁎) in the same patients.
We found that 7T MTR, in less than 10min scanning time, was able to detect cortical lesions. In this study we found that 7T MTR was better in detecting intracortical lesions in comparison with 7T T2(⁎), 7T MPRAGE, and 3T 3D DIR. since only a very few intracortical lesions were detected in healthy controls in our blind assessment, it is likely that the lesions detected represent focal grey matter demyelination. High resolution MT imaging has especially revealed cortical changes that have not been recognised by other MR sequences. MTR maps were noisier than MPRAGE, T2(⁎) and DIR, but also better in localising cortical lesions. As MTR is more pathologically specific than other sequences in detecting tissue myelination, it raises the possibility that high resolution MTR will be able to demonstrate cortical remyelination in vivo.
与白质（WM）病变相比，皮质病变在脑脱髓鞘病变中占比更大。在传统MRI上，它们常常被漏诊。最近的研究利用7T T2（⁎）、7T MPRAGE和3T DIR改善了皮质病变的检测，但似乎我们仍然只能检测到“冰山一角”。在本研究中，我们首次报告了在多发性硬化症（MS）中系统使用高分辨率磁化传递率（MTR），并将MTR病变检测与7T MPRAGE、7T T2（⁎）和3T 3D DIR进行比较。
我们报告在7T下使用高分辨率、快速磁化传递成像（MTI）在MS中检测皮质病变的情况。
对18例MS患者进行扫描（扩展残疾状态量表评分：3.0，平均年龄：48岁，平均病程：7.25年）。将扫描结果与9名健康对照者（平均年龄36.5岁）进行比较。
我们采集了7T MPRAGE图像、7T MTR图谱、7T T2（⁎）和3T 3D DIR。从MPRAGE图像中分割出WM并去除，以仅获得皮质灰质带（cGMR）掩码。然后将该掩码应用于先前已配准到MPRAGE容积上的不同模态（MPRAGE、MTR、DIR、T2（⁎）加权）。由两名对疾病状态不知情的观察者对cGMR进行分析。
在MS患者中，7T MTR共检测到365个病变（平均每位患者20.28个病变），7T MPRAGE检测到289个病变（平均16.06个病变），7T T2（⁎）检测到231个病变（平均12.83个病变）。在同一天进行3T 3D DIR扫描的8例MS患者中，共检测到136个病变（平均每位患者17个病变），而在同一患者中，7T MTR检测到171个病变，7T MPRAGE检测到147个病变，7T T2（⁎）检测到126个病变。
我们发现，在扫描时间不到10分钟的情况下，7T MTR能够检测到皮质病变。在本研究中，我们发现与7T T2（⁎）、7T MPRAGE和3T 3D DIR相比，7T MTR在检测皮质内病变方面表现更好。由于在我们的盲法评估中，健康对照者中仅检测到极少数皮质内病变，因此检测到的病变很可能代表局灶性灰质脱髓鞘。高分辨率MT成像尤其揭示了其他MR序列未识别的皮质变化。MTR图谱比MPRAGE、T2（⁎）和DIR噪声更大，但在定位皮质病变方面也更好。由于MTR在检测组织髓鞘化方面比其他序列在病理上更具特异性，因此提高了高分辨率MTR能够在体内显示皮质再髓鞘化的可能性。
