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| 7.0-T MR image of postmortem tissue sample used for histologic comparison.Source: Radiology |
Combined analysis of 7T R2* and phase data may be able to distinguish between changes in tissue myelin and iron in multiple sclerosis (MS) patients, and could help in characterizing the disease process of MS lesions, according to a study published in the Nov. 14 issue ofRadiology.Jeff H. Duyn, PhD, of the National Institutes of Health in Bethesda, Md., and colleagues wanted to test the effectiveness of recently available ultra-high-field-strength MRI systems in characterizing MS. Specifically, they wanted to see if the improved contrast of susceptibility-weighted 7T MRI images, which is highly variable within and among MS lesions, is correlated to levels of iron and myelin.The researchers obtained high-spatial-resolution susceptibility-weighted 7T MR images from 21 MS patients and investigated contrast patterns in quantitative phase and R2* images in areas defined as chronic MS lesions. Positive or negative phase shifts were assessed in each lesion. Duyn et al also performed postmortem MR imaging at 7T and 11.7T and the results were correlated with immunohistochemical staining for myelin, iron and ferritin.Results showed that 60.5 percent of the lesions had a normal phase and a reduced R2*, while 38.2 percent had negative phase shift and a variety of appearance on R2* maps. When compared with histologic findings, R2* reduction corresponded to severe loss of iron and myelin, while negative phase shift corresponded to focal iron deposits with myelin loss.“Changes in these parameters are interpreted as indicators of myelin and axon loss, which may follow the initial inflammatory process in MS-induced [white matter] lesions,” wrote the authors.
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