3 Tesla and 7 Tesla MRI of multiple sclerosis cortical lesions

Abstract

Cortical lesions are prevalent in multiple sclerosis but are poorly detected using MRI. The double inversion recovery (DIR) sequence is increasingly used to explore the clinical relevance of cortical demyelination. Here we evaluate the agreement between imaging sequences at 3 Tesla (T) and 7T for the presence and appearance of individual multiple sclerosis cortical lesions. Eleven patients with demyelinating disease and eight healthy volunteers underwent MR imaging at 3T (fluid attenuated inversion recovery [FLAIR], DIR, and T 1 -weighted magnetization prepared rapid acquisition gradient echo [MP-RAGE] sequences) and 7T (T 1 -weighted MP-RAGE). There was good agreement between images for the presence of mixed cortical lesions (involving both gray and white matter). However, agreement between imaging sequences was less good for purely intracortical lesions. Even after retrospective analysis, 25% of cortical lesions could only be visualized on a single MRI sequence. Several DIR hyperintensities thought to represent cortical lesions were found to correspond to signal arising from extracortical blood vessels. High-resolution 7T imaging appeared useful for confidently classifying the location of lesions in relation to the cortical/subcortical boundary. We conclude that DIR, FLAIR, and MP-RAGE imaging sequences appear to provide complementary information during the detection of multiple sclerosis cortical lesions. High resolution 7T imaging may facilitate anatomical localization of lesions in relation to the cortical boundary. GRAY MATTER BRAIN pathology was recognized in early neuropathological descriptions of multiple sclerosis (MS) but until recently it has received scant attention. Histology reveals cortical demyelinating lesions, a third of which simultaneously involve subcortical white matter. The finding of neuroaxonal injury within cortical lesions (1-3), along with the high frequency of cortical demyelination in the brains of patients with advanced disability (4), suggests that cortical demyelination could account for some chronic features of MS. The ability to address this hypothesis in vivo has been hindered so far by the low sensitivity of MRI to cortical demyelination.Postmortem MR imaging in MS patients has shown a 1.5 Tesla (T) fluid attenuated inversion recovery (FLAIR) sequence to detect 41% of mixed cortical/subcortical (C/SC) lesions and only 5% of intracortical (IC) lesions (5). The double inversion recovery (DIR) sequence uses two inversion pulses which null signal from both the normal-appearing white matter and the cerebrospinal fluid (CSF). DIR has been shown to increase the detection rate of intra-cortical lesions by 150% when compared with FLAIR in vivo (6-8), still predicting a sensitivity of only $12.5%. In vivo studies comparing FLAIR and DIR in patients with MS have analyzed total lesion number rather than investigating the agreement between sequences for individual cortical lesions (6,8).Factors precluding MRI visualization of cortical demyelination are likely to include the small volum...

Ultra-High-Field MRI Visualization of Cortical Multiple Sclerosis Lesions with T2 and T2*: A Postmortem MRI and Histopathology Study

“…18 This finding was supported by another study in which DIR detected 43% more cortical lesions than FLAIR. 9 However, a study from Kilsdonk et al 28 at ultra-high-field strength (7T) showed that FLAIR detected 89% more cortical lesions than DIR, and that DIR and T2WI obtained nearly identical mean cortical lesion counts (115 versus 116). This finding indicates that a sequence that may be optimal at a lower field strength (DIR at 3T) may lose its benefit at a higher field strength (7T), and vice versa: A sequence suboptimal at a lower field strength may have an advan- Note:-WM-WML indicates white matter-to-white matter lesion CNR; GM-GML, gray matter-to-gray matter lesion CNR; GM-WM, gray matter-to-white matter CNR.…”

“…The introduction of ultra-high-field MR imaging scanners and specific MR imaging pulse sequences has improved the detection of GM lesions due to a higher signal-to-noise ratio and better spatial resolution. [7][8][9] 7T T2*-weighted gradient-echo MR imaging has been shown to provide high-resolution anatomic images of GM lesions, and it has even been suggested that this sequence be used as the new criterion standard for GM lesion detection. 10 It was reported to be 44% more sensitive than 1.5T…”

Multicontrast MR Imaging at 7T in Multiple Sclerosis: Highest Lesion Detection in Cortical Gray Matter with 3D-FLAIR

“…In the present literature, there are several studies that focus on the detection of cortical GM lesions at 7T, [17][18][19]33,34 mostly reporting that T2*-weighted gradient-echo sequences improve detection. One of these studies by using T2*-weighted gradient-echo images even suggested that this sequence should be the new criterion standard for the detection of cortical lesions in patients with MS. 33 Another recent study reported that white matter signal attenuation at 7T is feasible and is able to detect cortical abnormalities at 7T.…”

“…One of these studies by using T2*-weighted gradient-echo images even suggested that this sequence should be the new criterion standard for the detection of cortical lesions in patients with MS. 33 Another recent study reported that white matter signal attenuation at 7T is feasible and is able to detect cortical abnormalities at 7T. 35 To our knowledge, the value of the recommended sequences for clinical use at 7T has not yet been investigated nor has the use of DIR.…”

Ultrahochfeld-MRT im Kontext neurologischer Erkrankungen

“…Auch im Vergleich zur 3-T-Bildgebung besteht ein nachgewiesener quantitativer [20] und qualitativer [107] Vorteil der UHF-Bildgebung bei der Darstellung der KL. Darauf aufbauend konnte in zwei Studien nachgewiesen werden, dass MS-Patienten mit einer höheren subpialen Läsionslast (Typ III) signifikant höhere Werte auf der Expanded Disability Status Scale (EDSS) aufweisen [18,70].…”