7T MP2RAGE MRI for assessment of myelination status in white matter lesions of multiple sclerosis
ECTRIMS Online Library. Kolb H. Oct 12, 2018; 232022; 269
Hadar Kolb
Hadar Kolb

Abstract: 269

Type: Scientific Session

Abstract Category: Pathology and pathogenesis of MS - MRI and PET

Introduction: Histopathologically, chronic MS lesions can be broadly classified according to myelin content, axonal loss, and inflammation. A similar, noninvasive lesion classification is currently not feasible. The longitudinal MRI relaxation time constant (T1) is known to be affected by lipid protons, including those in myelin, and thus is a good candidate to be a noninvasive marker of myelin content in white matter.
Purpose: To investigate 7T T1 mapping using MP2RAGE for broad classification of myelin content in chronic MS lesions.
Methods: We studied 29 lesions from 3 postmortem MS brains radiologically and histologically. Based on initial observations of a possible trichotomy in lesion appearance. Lesions - identified as white matter areas with prolonged T1 - were prospectively classified on 7T T1 maps as CSF-like (long T1), cortical gray matter-like (intermediate T1), or mixed; lesion-specific T1 values were also computed. Myelin, axonal loss, and inflammation were assessed histologically. As a first in vivo application, we performed a similar analysis of T1 maps in 236 lesions from 14 MS patients, the ages of which were derived from the presence of gadolinium enhancement on a prior NIH scan.
Results: In the postmortem study, long-T1 lesions corresponded to fully demyelinated plaques, short-T1 lesions to shadow plaques, and mixed lesions to a combination of both. After manual classification of the in vivo images, T1 values differed between the 3 groups: “remyelinated” (mean ± SD: 1625±246), “demyelinated” (2807±244), “mixed” (2143±191) (p< 0.001). “Demyelinated” lesions were older (6.3±3.1 years) than “remyelinated” lesions (2.8±2.4) (p< 0.001) and were found in older patients (46±6 vs 41±5, p< 0.0001), despite no differences in age at disease onset or lesion formation.
Conclusion: 7T T1 mapping with MP2RAGE allows qualitative and quantitative classification of chronic MS lesions according to myelin content. Longitudinal studies are needed to assess the prognostic value of different lesion types and to tighten radiological and clinical correlation. Further, 3T and 7T MP2RAGE comparison trials are necessary to establish MP2RAGE as a robust and practical imaging marker of remyelination.
Disclosure: Dr. Absinta is supported by the Intramural Research Program of NINDS, by the Conrad N. Hilton Foundation (grant #EIN 15-20858115) and by the National Multiple Sclerosis Society (NMSS) (grant #FG 2093-A-1).

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