Quantitative Magnetic Resonance Of Postmortem Multiple Sclerosis Brain Before And After Fixation
Schmierer K, Wheeler-Kingshott CA, Tozer DJ, Boulby PA, Parkes HG, Yousry TA, Scaravilli F, Barker GJ, Tofts PS, Miller DH
Magn Reson Med 2008 Feb;59(2):268-77
NMR Research Unit, Institute of Neurology, University College London, Queen Square, London, UK
Unfixed and fixed postmortem Multiple Sclerosis (MS) Brain is being used to probe pathology underlying quantitative MR (qMR) changes. Effects of fixation on qMR indices in MS Brain are unknown.
In 15 postmortem MS Brain slices T1, T2, MT Ratio (MTR), MacroMolecular Proton Fraction (f(B)), Fractional Anisotropy (FA), and Mean, Axial, and Radial Diffusivity (MD, D(ax), and D(rad)).
Were assessed in White Matter (WM) Lesions (WML) and Normal-Appearing WM (NAWM) before and after fixation in formalin.
Myelin content, Axonal count, and Gliosis were quantified Histologically. Student's t-test and regression were used for analysis.
T1, T2, MTR, and f(B) obtained in unfixed MS Brain were similar to published values obtained in patients with MS in vivo.
Following fixation T1, T2 (NAWM, WML) and MTR (NAWM) dropped, whereas f(B) (NAWM, WML) increased.
Compared to published in vivo data all Diffusivity measures were lower in unfixed MS Brain, and dropped further following fixation (except for FA).
MTR was the best predictor of T(Myelin) (inversely related to Myelin) in unfixed MS Brain (r = -0.83; P < 0.01).
Whereas, postfixation T2 (r = 0.92; P < 0.01), T1 (r = 0.89; P < 0.01), and f(B) (r = -0.86; P < 0.01) were superior. All Diffusivity measures (except for D(ax) in unfixed tissue) were predictors of Myelin content.
(c) 2008 Wiley-Liss, Inc.
Characteristics Of Abnormal Diffusivity In Normal-Appearing White Matter Investigated With Diffusion Tensor MR Imaging In Tuberous Sclerosis Complex
Makki MI, Chugani DC, Janisse J, Chugani HT
AJNR Am J NeuroRadiol 2007 Oct;28(9):1662-7
Children's Hospital of Michigan, Carman and Ann Adams Department of Pediatrics, Detroit, MI 48201, USA
Background And Purpose
Although patients with Tuberous Sclerosis Complex (TSC) manifest various structural abnormalities, we hypothesized that White Matter (WM) structures that appear normal on conventional MR imaging may be accompanied by MicroStructural changes, such as Gliosis and Myelinization defects.
Our objective was to determine in vivo whether there was evidence for WM MicroStructural changes by using Diffusion Tensor Imaging (DTI).
Materials And Methods
We used DTI to evaluate Diffusivity and Anisotropy in Normal-Appearing WM (NAWM) of 6 children with TSC and 12 age-matched control subjects.
The anterior and posterior limbs of the Internal Capsule, the External Capsule, and the Genu and Splenium of the Corpus Callosum were assessed.
We hypothesized that previously reported DTI abnormalities of NAWM in patients with TSC may not be equal in all Diffusion directions as measured by the major, middle, and minor eigenvalues.
When combining NAWM regions in patients with TSC, we observed a significant increase in Mean Diffusivity (P = .003) and a decrease in Anisotropy (P = .03) compared with those of controls.
However, the increase in Diffusivity was more pronounced in directions orthogonal to the Axons measured by the minor and middle eigenvalues (P = .005) than by the major eigenvalue (P = .02).
Our findings revealed a decrease in Anisotropy and an increase in longitudinal and Radial Diffusivities in NAWM beyond the location of TSC lesions seen on conventional MR imaging.
The Axonal MicroStructural changes suggested by our study may be related to changes in Myelin packing due to Giant Cells accompanied by Gliosis and Myelination defects known to occur in TSC WM.
Application Of Voxelwise Analysis In The Detection Of Regions Of Reduced Fractional Anisotropy In Multiple Sclerosis Patients
Patel SA, Hum BA, Gonzalez CF, Schwartzman RJ, Faro SH, Mohamed FB
J Magn Reson Imaging 2007 Sep;26(3):552-6
Drexel University, Department of Biomedical Engineering, Philadelphia, Pennsylvania, USA
To investigate the utility of voxelwise analysis in the detection of lesions in the Normal-Appearing White Matter (NAWM) of individual Multiple Sclerosis (MS) patients.
Materials And Methods
Diffusion Tensor Imaging (DTI) was performed on 10 normal controls and six patients with MS lesions.
The Fractional Anisotropy (FA) maps derived from the Diffusion-weighted images were then spatially normalized (via an affine transformation) into Montreal Neurological Institute (MNI) space.
And, the normalized FA map of each of the patients was compared voxelwise with the normalized FA maps of the group of normals in a one-sample t-test (P = 0.0001).
Two independent board-certified NeuroRadiologists reviewed the data.
In the patient data for all six cases, the two reviewers determined detection sensitivities of 72% and 96% for the voxelwise technique based on known Fluid-Attenuated Inversion-Recovery (FLAIR) lesions.
In addition, between the two reviewers, nine NAWM regions exhibiting FA reductions were identified in the six patients.
However, numerous regions of abnormal FA were detected that were attributed to poor intersubject image registration.
Voxelwise analysis of spatially normalized FA maps has the potential to identify regions of FA reduction in lesions and in the NAWM of individual MS patients in a rapid and reproducible fashion.
J. Magn. Reson. Imaging 2007;26:552-556. (c) 2007 Wiley-Liss, Inc.
Diffusion Tensor MR Imaging Of The Cervical Spinal Cord In Patients With Multiple Sclerosis
Ohgiya Y, Oka M, Hiwatashi A, Liu X, Kakimoto N, Westesson PL, Ekholm SE
Eur Radiol 2007 Oct;17(10):2499-504
University of Rochester Medical Center, Division of Diagnostic and Interventional NeuroRadiology, Department of Imaging Science, Rochester, NY, USA
Our purpose was to evaluate the ability of Diffusion Tensor Imaging (DTI) to characterize Cervical Spinal Cord White Matter (WM) in patients with Multiple Sclerosis (MS).
DTI were obtained in 21 MS patients and 21 control subjects (CS). Regions Of Interest (ROIs) were placed at C2/3, C3/4, and C4/5 within the right, left, and dorsal (WM) to calculate Fractional Anisotropy (FA) and the Apparent Diffusion Coefficient (ADC).
Measurements in plaques and Normal-Appearing White Matter (NAWM) of MS patients were compared with mean FA and ADC of WM in CS. FA was significantly lower in all regions in MS patients than in CS.
ADC was significantly higher in all regions in MS patients than in CS except for in the dorsal WM at C2/3 and the bilateral WM at C4/5. The mean FA was 0.441 for plaques and 0.542 for NAWM, as compared with 0.739 in CS.
The mean ADC was 0.810 x 10(-3) mm(2)/s for plaques and 0.722 x 10(-3) mm(2)/s for NAWM, as compared with 0.640 x 10(-3) mm(2)/s for CS. FA and ADC showed significant differences between plaques, NAWM and control WM(P < 0.01).