Advanced MRI Section, Laboratory of Functional Molecular Imaging, and Neuroimmunology Branch, Neurologic Disorders and Stroke, National Institutes of Health, 10 Center Dr, Bldg 10, Bethesda, MD 20892-1065, USA.
Radiology. 2012 Jan;262(1):206-15. doi: 10.1148/radiol.11110601. Epub 2011 Nov 14.
To elucidate the mechanism of magnetic resonance (MR) imaging contrast in multiple sclerosis (MS) lesion appearance by using susceptibility-weighted imaging and to assess with histologic correlation the role of iron and myelin in generating this MR imaging contrast.
Each patient provided written consent to a human subject protocol approved by an institutional review board. High-spatial-resolution susceptibility-weighted 7.0-T MR images were obtained in 21 patients with MS. Contrast patterns in quantitative phase and R2* images, derived from 7.0-T data, were investigated in 220 areas defined as chronic MS lesions on conventional T2-weighted fluid-attenuated inversion recovery, T2-weighted, and T1-weighted spin-echo images. The presence of positive or negative phase shifts (ie, decreased or increased MR frequency, respectively) was assessed in each lesion. In addition, postmortem MR imaging was performed at 7.0 T and 11.7 T, and its results were correlated with those of immunohistochemical staining specific for myelin, iron, and ferritin.
The majority (133 [60.5%] of 220) of the identified lesions had a normal phase and reduced R2*. A substantial fraction of the lesions (84 [38.2%] of 220) had negative phase shift, either uniformly or at their rim, and a variety of appearances on R2* maps. These two lesion contrast patterns were reproduced in the postmortem MR imaging study. Comparison with histologic findings showed that, while R2* reduction corresponded to severe loss of both iron and myelin, negative phase shift corresponded to focal iron deposits with myelin loss.
Combined analysis of 7.0-T R2* and phase data may help in characterizing the pathologic features of MS lesions. The observed R2* decreases suggest profound myelin loss, whereas negative phase shifts suggest a focal iron accumulation.
通过使用磁敏感加权成像阐明多发性硬化症（MS）病变外观的磁共振（MR）成像对比的机制，并通过组织学相关性评估铁和髓鞘在产生这种 MR 成像对比中的作用。
每位患者均书面同意了机构审查委员会批准的人体研究方案。在 21 例 MS 患者中获得了高空间分辨率的磁敏感加权 7.0-T MR 图像。在常规 T2 加权液体衰减反转恢复、T2 加权和 T1 加权自旋回波图像上定义为慢性 MS 病变的 220 个区域中，研究了来自 7.0-T 数据的定量相位和 R2*图像的对比模式。评估了每个病变的相位是否存在正或负移（即，MR 频率分别降低或增加）。此外，在 7.0 T 和 11.7 T 进行了死后 MR 成像，并将其结果与针对髓鞘、铁和铁蛋白的免疫组织化学染色结果相关联。
大多数（220 个病变中的 133 个，60.5%）识别的病变具有正常的相位和降低的 R2*。相当一部分病变（220 个病变中的 84 个，38.2%）具有负的相位偏移，无论是均匀的还是在其边缘，并在 R2图谱上具有各种外观。这两种病变对比模式在死后 MR 成像研究中得到了再现。与组织学发现的比较表明，虽然 R2降低对应于铁和髓鞘的严重丢失，但负的相位偏移对应于铁沉积伴髓鞘丢失。
7.0-T R2和相位数据的综合分析可能有助于表征 MS 病变的病理特征。观察到的 R2降低表明髓鞘严重丢失，而负相位偏移提示局部铁积累。
