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Increased mean R2* in the deep gray matter of multiple sclerosis patients: Have we been measuring atrophy?

Authors :
Hernández‐Torres, Enedino
Wiggermann, Vanessa
Machan, Lindsay
Sadovnick, A. Dessa
Li, David K.B.
Traboulsee, Anthony
Hametner, Simon
Rauscher, Alexander
Hernández-Torres, Enedino
Source :
Journal of Magnetic Resonance Imaging; Jul2019, Vol. 50 Issue 1, p201-208, 8p
Publication Year :
2019

Abstract

<bold>Background: </bold>Magnetic resonance relaxometry studies in multiple sclerosis (MS) have suggested that iron accumulates within deep gray matter (DGM) structures early in the disease course. However, the commonly utilized mean R2* and magnetic susceptibility measures reflect regional iron concentration but not a structure's total iron content. Thus, tissue atrophy could impact mean R2* and magnetic susceptibility estimates.<bold>Purpose: </bold>To demonstrate that both average iron concentration and total iron content need to be reported in order to distinguish between atrophy-related and definite magnetic susceptibility changes.<bold>Study Type: </bold>Observational.<bold>Population: </bold>The study was performed on 30 healthy controls (HCs) and 39 people with definite MS.<bold>Field Strength/sequence: </bold>3T Philips Achieva using an 8-channel SENSE head coil. R2* data were acquired using a multiecho gradient echo sequence and diffusion tensor imaging data were acquired using an echo-planar sequence.<bold>Assessment: </bold>Total iron content in DGM structures was assessed by calculating the sum of all R2* values within a region (denoted as R2mass* ) and compared to the mean R2* as a measure of iron concentration.<bold>Statistical Test: </bold>Significant group differences were investigated in a linear regression model. All DGM structures were assessed individually and the significance threshold was adjusted using the Bonferroni-Holm correction for multiple comparisons.<bold>Results: </bold>There was an increased mean DGM R2* in MS patients compared to HCs (significant in the pallidus, P = 0.0051). In contrast, R2mass* in patients was found to be lower in the thalamus and the caudate (P = 0.0011) compared to HCs, and similar between the two cohorts in the other DGM regions.<bold>Data Conclusion: </bold>An increase in mean R2* may not necessarily reflect increased iron accumulation. We propose R2mass* as an additional metric to account for the effects of tissue atrophy when assessing tissue content changes, such as iron deposition or loss.<bold>Level Of Evidence: </bold>1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:201-208. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
10531807
Volume :
50
Issue :
1
Database :
Complementary Index
Journal :
Journal of Magnetic Resonance Imaging
Publication Type :
Academic Journal
Accession number :
137028945
Full Text :
https://doi.org/10.1002/jmri.26561