Comparison of Multiple Sclerosis Cortical Lesion Types Detected by Multicontrast 3T and 7T MRI

Abstract

BACKGROUND AND PURPOSE: Our aims were the following: 1) to compare multicontrast cortical lesion detection using 3T and 7T MR imaging, 2) to compare cortical lesion type frequency in relapsing-remitting and secondary-progressive MS, and 3) to assess whether detectability is related to the magnetization transfer ratio, an imaging marker sensitive to myelin content. MATERIALS AND METHODS: Multicontrast 3T and 7T MR images from 10 participants with relapsing-remitting MS and 10 with secondaryprogressive MS. We used the following 3T contrast sequences: 3D-T1-weighted, quantitative T1, FLAIR, magnetization-transfer, and 2D proton-density-and T2-weighted. We used the following 7T contrast sequences: 3D-T1-weighted, quantitative T1, and 2D-T2 *-weighted. RESULTS: Cortical lesion counts at 7T were the following: 720 total cortical lesions, 420 leukocortical lesions (58%), 27 intracortical lesions (4%), and 273 subpial lesions (38%). Cortical lesion counts at 3T were the following: 424 total cortical, 393 leukocortical (93%), zero intracortical, and 31 subpial (7%) lesions. Total, intracortical, and subpial 3T lesion counts were significantly lower than the 7T counts (P Ͻ .002). Leukocortical lesion counts were not significantly different between scanners. Total and leukocortical lesion counts were significantly higher in secondary-progressive MS, at 3T and 7T (P Յ .02). Subpial lesions were significantly higher in secondary-progressive MS at 7T (P ϭ .006). The magnetization transfer ratio values of leukocortical lesions visible on both scanners were significantly lower than the magnetization transfer ratio values of leukocortical lesions visible only at 3T. No significant difference was found in magnetization transfer ratio values between subpial lesions visible only at 7T and subpial lesions visible on both 3T and 7T. CONCLUSIONS: Detection of leukocortical lesions at 3T is comparable with that at 7T MR imaging. Imaging at 3T is less sensitive to intracortical and subpial lesions. Leukocortical lesions not visible on 7T T2*-weighted MRI may be associated with less demyelination than those that are visible. Detectability of subpial lesions does not appear to be related to the degree of demyelination. ABBREVIATIONS: CL ϭ cortical lesion; IC ϭ intracortical; LC ϭ leukocortical; MTR ϭ magnetization transfer ratio; NAcGM ϭ normal-appearing cortical GM; RRMS ϭ relapsing-remitting MS; SP ϭ subpial; SPMS ϭ secondary-progressive MS M ultiple sclerosis is an inflammatory and neurodegenerative disease characterized by lesions that affect the white matter and gray matter of the central nervous system. 1 MR imaging of the brain is the criterion standard method to detect MS lesions in vivo, 2 allowing an accurate quantification of the WM component of MS. However, correlations between a patient's clinical status and WM lesion load remain modest 3,4 , so it is

New Prospects for Ultra-High-Field Magnetic Resonance Imaging in Multiple Sclerosis

“… 82 These results were confirmed in a recent study including 20 MS patients. 83 A postmortem study in brain sections of 19 MS patients using T1w, T2w, T2-FLAIR, DIR, or T2*w further substantiated this finding. 14 Of note, this study found a similarly low sensitivity of 7% to detect subpial lesions for DIR both at 3 and 7 T. Results from 1 study suggested that 7-T T2-FLAIR shows higher sensitivity at detecting cortical lesions compared with DIR, T2w, or T1w images.…”

Ultra-high-field 7-T MRI in multiple sclerosis and other demyelinating diseases: from pathology to clinical practice

“…Due to an increased spatial resolution and better tissue contrast, 7-T MRI has allowed a more accurate detection and characterisation of cortical GM lesions [28][29][30][31][32][33]. Cortical lesions are very common at histopathological examination, especially in the progressive forms of MS [34].…”

“…Moreover, cortical lesions are associated with disability progression [ 36 ] and cognitive impairment and could thus represent an important biomarker in the evaluation of progression of disease burden in MS. Focal cortical lesions are poorly visualised using conventional MRI sequences at 1.5 T [ 37 ] and 3 T, because of their small size, lower amount of inflammation than WM lesions, and partial volume effects with CSF. Since the first ex vivo and in vivo applications, it was clear that 7-T MRI improves not only detection of cortical lesions compared to 3-T MRI [ 29 , 30 , 38 ], but it also improves lesion localisation and classification [ 28 , 30 ]. A recent study by Treaba et al [ 32 ] found that cortical lesions predominantly develop intracortically and within sulci, supporting an inflammatory cerebrospinal fluid-mediated lesion pathogenesis of those lesions, as already suggested by MRI-pathological correlation studies [ 39 , 40 ] (Fig.…”

Ultra-high field 7 T imaging in multiple sclerosis

“…Other contrasts have been tested and optimized at 7T [6][7][8] to identify sequenced with the highest value for detecting CL in clinic. The comparison of T2 * contrast at 7T with 3T double inversion recovery 9 sequence or multicontrast data 10 that are more accessible in clinic demonstrated the superiority of the T2 * -sequence at 7T in detecting intracortical, especially subpial, lesions. Despite this, leukocortical lesion identification at 7T remains similar to that achieved at 3T 10 .…”

“…The comparison of T2 * contrast at 7T with 3T double inversion recovery 9 sequence or multicontrast data 10 that are more accessible in clinic demonstrated the superiority of the T2 * -sequence at 7T in detecting intracortical, especially subpial, lesions. Despite this, leukocortical lesion identification at 7T remains similar to that achieved at 3T 10 . The sensitivity of CL detection, however, cannot be inferred from imaging alone without histopathology validation.…”