Harrison D M, Li X, Liu H, Jones C K, Caffo B, Calabresi P A, van Zijl P
From the Department of Neurology (D.M.H.), University of Maryland School of Medicine, Baltimore, Maryland Departments of Neurology (D.M.H., P.A.C.)
Radiology and Radiological Science (X.L., C.K.J., P.v.Z.) F.M. Kirby Research Center for Functional Brain Imaging (X.L., H.L., C.K.J., P.v.Z.), Kennedy Krieger Institute, Baltimore, Maryland.
AJNR Am J Neuroradiol. 2016 Aug;37(8):1447-53. doi: 10.3174/ajnr.A4726. Epub 2016 Mar 3.
Susceptibility MR imaging contrast variations reflect alterations in brain iron and myelin content, making this imaging tool relevant to studies of multiple sclerosis lesion heterogeneity. In this study, we aimed to characterize the relationship of high-field, susceptibility contrasts in multiple sclerosis lesions to clinical outcomes.
Twenty-four subjects with multiple sclerosis underwent 7T MR imaging of the brain, disability examinations, and a fatigue inventory. The inverse of T2* relaxation time (R2*), frequency, and relative susceptibility (from quantitative susceptibility mapping) were analyzed in 306 white matter lesions.
Most lesions were hypointense on R2* (88% without a rim, 5% with). Lesions that were hyperintense on quantitative susceptibility mapping were more frequent in relapsing-remitting than in progressive multiple sclerosis (54% versus 35%, P = .018). Hyperintense lesion rims on quantitative susceptibility maps were more common in progressive multiple sclerosis and patients with higher levels of disability and fatigue. Mean lesion R2* was inversely related to disability and fatigue and significantly reduced in progressive multiple sclerosis. Relative susceptibility was lower in lesions in progressive multiple sclerosis (median, -0.018 ppm; range, -0.070 to 0.022) than in relapsing-remitting MS (median, -0.010 ppm; range, -0.062 to 0.052; P = .003).
A progressive clinical phenotype and greater disability and fatigue were associated with lower R2* and relative susceptibility values (suggestive of low iron due to oligodendrocyte loss) and rimmed lesions (suggestive of chronic inflammation) in this multiple sclerosis cohort. Lesion heterogeneity on susceptibility MR imaging may help explain disability in multiple sclerosis and provide a window into the processes of demyelination, oligodendrocyte loss, and chronic lesion inflammation.
磁共振成像（MRI）的磁化率对比变化反映了脑内铁和髓鞘含量的改变，使得这种成像工具与多发性硬化症病变异质性研究相关。在本研究中，我们旨在描述多发性硬化症病变的高场磁化率对比与临床结局之间的关系。
24例多发性硬化症患者接受了脑部7T磁共振成像、残疾检查和疲劳量表评估。对306个白质病变的T2弛豫时间倒数（R2）、频率和相对磁化率（来自定量磁化率成像）进行了分析。
大多数病变在R2上呈低信号（88%无边缘，5%有边缘）。定量磁化率成像上呈高信号的病变在复发缓解型多发性硬化症中比进展型多发性硬化症中更常见（54%对35%，P = 0.018）。定量磁化率图上的高信号病变边缘在进展型多发性硬化症以及残疾和疲劳程度较高的患者中更常见。平均病变R2与残疾和疲劳呈负相关，在进展型多发性硬化症中显著降低。进展型多发性硬化症病变的相对磁化率低于复发缓解型多发性硬化症（中位数，-0.018 ppm；范围，-0.070至0.022）（中位数，-0.010 ppm；范围，-0.062至0.052；P = 0.003）。
在这个多发性硬化症队列中，进展性临床表型以及更大的残疾和疲劳与较低的R2*和相对磁化率值（提示少突胶质细胞丢失导致铁含量低）以及有边缘的病变（提示慢性炎症）相关。磁化率MRI上的病变异质性可能有助于解释多发性硬化症中的残疾情况，并为脱髓鞘、少突胶质细胞丢失和慢性病变炎症过程提供一个窗口。
