Does high-field MR imaging improve cortical lesion detection in multiple sclerosis?
OBJECTIVE
Cortical lesions in multiple sclerosis (MS) are notoriously difficult to visualize with standard MR imaging (MRI) techniques. However, the use of higher field-strengths with intrinsically higher signal-to-noise, which can partly be used to increase spatial resolution, may improve cortical lesion detection. Therefore, in this post mortem study, the sensitivity of high field-strength MRI (4.7 T) for cortical lesions was investigated, and compared to that of standard field-strength (1.5 T).


METHODS
At 1.5 T, dual-echo T2-weighted spin-echo, as well as 3D-FLAIR images of seventeen formalin-fixed coronal MS and four control hemispheres were acquired. At 4.7 T, the same specimens were imaged with a mainly proton-density (PD)- weighted sequence. Proteolipid protein (PLP)-stained tissue sections (10 microm) of the same brain slices were matched to the corresponding MR images, and cortical lesions were scored on all three MR sequences (blinded to histology) and in tissue sections (blinded to MRI). Sensitivity of the sequences for four cortical lesion types was calculated. Additionally, an unblinded, retrospective MR scoring was performed.


RESULTS
Sensitivity for purely intracortical lesions (histological lesion types II, III, and IV; n = 128) was below 10 % for both 1.5 T and 4.7 T MRI, while mixed gray matter-white matter (type I) lesions (n = 5) were detected in four out of five cases. All lesion counts increased upon retrospective (unblinded) scoring. However, up to 80% of the intracortical lesions still remained undetected.


CONCLUSIONS
MRI sensitivity for post mortem detection of cortical lesions is low, even when a higher field-strength was used. It varies, however, for different subtypes of cortical lesions.
Geurts
Jeroen J G
JJ
Department of Radiology, VU University Medical Center, De Boelelaan 1117, Amsterdam, The Netherlands. j.geurts@vumc.nl
Blezer
Erwin L A
EL
Vrenken
Hugo
H
van der Toorn
Annette
A
Castelijns
Jonas A
JA
Polman
Chris H
CH
Pouwels
Petra J W
PJ
Bö
Lars
L
Barkhof
Frederik
F
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D001344:Autopsy; D002540:Cerebral Cortex / Q000473:pathology*; D005260:Female; D005404:Fixatives; D005557:Formaldehyde; D006801:Humans; D007150:Immunohistochemistry; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000473:pathology*; D012189:Retrospective Studies; D016707:Tissue Fixation
D005404:Fixatives; D005557:Formaldehyde