Magnetization Transfer Imaging To Monitor The Evolution Of Multiple Sclerosis
Ital J Neurol Sci 1999;20(5 Suppl):S232-40
Scientific Institute, Ospedale San Raffaele, NeuroImaging Research Unit,
Univ of Milan, Dept of NeuroScience, Milan, Italy
PMID# 10662954; UI# 20314530
Magnetization Transfer Imaging (MTI) is a Magnetic Resonance Imaging (MRI) technique that is now used in Multiple Sclerosis (MS) studies, and is thought to have a higher pathological specificity than conventional T2-weighted imaging.
This review outlines the major contributions given by MTI for the understanding of MS evolution.
MTI studies of individual MS lesions confirm the pathological Heterogeneity of T2-weighted MRI abnormalities and the potential role of unenhanced T1-weighted HypoIntensities as specific markers of localized severe White Matter disruption.
Correlative cross-sectional and longitudinal studies using MTI and Gadolinium (Gd)-enhanced MRI reveal that MTI findings may vary in Lesions.
With different patterns of enhancement and that MTI abnormalities are closely related to the onset and recovery of Blood-Brain Barrier disruption in new MS plaques.
MTI Lesion Load (LL) is highly correlated with T2-weighted MRI lesion load, but it has a limited reliability as a measure of MS lesion burden.
On the other hand, measures obtained from MT scans using whole-Brain Histogram analysis are highly correlated with the extent of MS abnormalities on conventional MRI scans.
And predict patients' clinical Disability well, Since they are sensitive to both macro- and microscopic MS lesion burden in the whole Brain and in specific regions.
These data suggest that:
- MTI is sensitive to different stages of lesion pathology and pathological evolution in MS patients
- MTR Histogram analysis can provide a more global assessment of MS lesion burden, since it encompasses both Macro- and Microscopic MS pathology
Guo AC, MacFall JR, Provenzale JM
Radiology 2002 Mar;222(3):729-36
Duke University Medical Center, Department of Radiology, Box 3808, Rm 1533, Erwin Rd, Durham, NC 27710-3808, USA
PMID# 11867792; UI# 21857029
To determine whether the Normal-Appearing White Matter (NAWM) regions surrounding and remote from Multiple Sclerosis (MS) plaques have abnormal Diffusional Anisotropy.
And, to compare Anisotropy maps with Apparent Diffusion Coefficient (ADC) maps for sensitivity in the detection of White Matter (WM) abnormalities.
Materials And Methods
Conventional and Diffusion Tensor Magnetic Resonance (MR) imaging examinations were performed in 26 patients with MS and in 26 age-matched control subjects.
Fractional Anisotropy (FA) and ADC maps were generated and coregistered with T2-weighted MR images.
Uniform regions of interest were placed on plaques, PeriPlaque White Matter (PWM) regions, NAWM regions in the ContraLateral side of the Brain, and WM regions in control subjects to obtain FA and ADC values, which were compared across the WM regions.
The mean FA was 0.280 for plaques, 0.383 for PWM, 0.493 for NAWM, and 0.537 for control subject WM.
The mean ADC was 1.025 x 10(-3) mm(2)/sec for plaques, 0.786 x 10(-3) mm(2)/sec for PWM, 0.739 x 10(-3) mm(2)/sec for NAWM, and 0.726 x 10(-3) mm(2)/sec for control subject WM.
Significant differences in Anisotropy and ADC values were observed among all WM regions (P < .001 for all comparisons, except ADC in NAWM vs control subject WM [P =.018]).
The Anisotropy and ADC values were abnormal in all WM regions in the patients with MS and were worse in the PeriPlaque regions than in the distant regions.
Diffusion Tensor MR imaging may be more accurate than T2-weighted MR imaging for assessment of disease burden.
Quantitative Magnetization Transfer Imaging Of Pre-Lesional White-Matter Changes In Multiple Sclerosis
Fazekas F, Ropele S, Enzinger C, Seifert T, Strasser-Fuchs S
Mult Scler 2002 Dec;8(6):479-84
Karl-Franzens-University Graz, Department of Neurology, Auenbruggerplatz 22, A-8036 Graz, Austria
Previous Magnetization Transfer (MT) studies in Multiple Sclerosis (MS) suggest a reduction of the MT Ratio (MTR) precedes new lesion development.
To gain further insight into pre-lesional tissue abnormalities, we investigated the time course of additional quantitative MT parameters.
Serial Magnetic Resonance Imaging (MRI), including a Gadolinium-enhanced T1 scan and MT imaging by means of a FastPACE sequence, was performed on 12 patients (4 males, 8 females) with Relapsing/Remitting MS.
Quantitative MT values including the Magnetization Exchange Rate (k for) and the native relaxation time (T1 free) were analyzed in the six months prior to the appearance of 44 enhancing lesions and in 88 control regions of persistently Normal-Appearing White Matter (NAWM).
Appearance of new active lesions was preceded by a significant decrease of the MTR (F7,166=91.5; p< 0.0001) and of k for (F7,166=105.2; p< 0.0001), and by an increase of T1 free (F7,166=57.3; p< 0.0001).
The drop of k for was the most pronounced pre-lesional change and together with the MTR was statistically significant already four months before the appearance of new lesion.
The observed increase of T1 free was relatively small. MT variables of reactivated lesions were always different from NAWM but showed no characteristic time course.
Multiparametric MT measurements suggest both a reduction of macromolecular material and a focal increase of free water to occur several months before the appearance of an active lesion.
Reduction of the Magnetization Exchange Rate, which may result from primary damage to Myelin, appears to be the leading event.
Magnetization Transfer Ratio Measurement In Multiple Sclerosis Normal-Appearing Brain Tissue: Limited Differences With Controls But Relationships With Clinical And MR Measures Of Disease
Vrenken H, Pouwels PJ, Ropele S, Knol DL, Geurts JJ, Polman CH, Barkhof F, Castelijns JA
Mult Scler 2007 Jul;13(6):708-16
MR Center for MS Research, VU University Medical Center, Department of Radiology, Amsterdam, The Netherlands
We investigated the Magnetization Transfer Ratio (MTR) of Normal-Appearing White (NAWM) and Gray Matter (NAGM) in a relatively large group of Multiple Sclerosis (MS) patients, and the relations of MTR changes with clinical disability.
MTR was measured in 66 MS patients (12 PP, 35 RR, 19 SP) and 23 healthy controls, using a Whole-Brain 3D-FLASH technique corrected post-hoc for B1-induced variation.
Histogram parameters of conservatively selected NAWM and Cortical NAGM were analyzed using Bonferroni-corrected ANOVA with age as covariate.
Additionally, manually outlined Regions Of Interest were analyzed using a multilevel method.
Lesions had low MTR (mean 22.7+/-6.9%), but NAWM exhibited limited changes: MTR Histogram peak position was 32.8+/-1.0% in controls and 32.4+/-0.9% in MS patients, with a significant decrease compared to controls only in SPMS patients (31.9+/-1.1%, p=0.045).
Cortical MTR Histogram did not differ significantly between patients and controls. In SPMS, regional mean MTR was significantly decreased in Corpus Callosum and Hippocampus.
MTR Histogram parameters of NAGM and NAWM were correlated with EDSS and MSFC scores, with lesion volume and with Normalized Brain Volume.
We conclude that disease-induced MTR changes were small in MS NAWM and NAGM, but did correlate with clinical decline, Lesion Volume and overall Cerebral Atrophy.