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Multiple sclerosis, magnetic resonance imaging, scanner-related variability
Abstract:
Brain volumetric measurements in multiple sclerosis (MS) reflect not
only disease-specific processes but also other sources of variability.
The latter has to be considered especially in multicenter and
longitudinal studies. Here, we compare data generated by three different
3-Tesla magnetic resonance scanners (Philips Achieva; Siemens Verio; GE
Signa MR750). We scanned two patients diagnosed with relapsing remitting
MS six times per scanner within three weeks (T1w and FLAIR, 3D). We
assessed T2-hyperintense lesions by an automated lesion segmentation
tool and determined volumes of grey matter (GM), white matter (WM) and
whole brain (GM + WM) from the lesion-filled T1-weighted images using
voxel-based morphometry (SPM8/VBM8) and SIENAX (FSL). We measured
cortical thickness using FreeSurfer from both, lesion-filled and
original T1-weighted images. We quantified brain volume changes with
SIENA.
In both patients, we found significant differences in total lesion
volume, global brain tissue volumes and cortical thickness measures
between the scanners. Morphometric measures varied remarkably between
repeated scans at each scanner, independent of the brain imaging
software tool used.
We conclude that for cross-sectional multicenter studies, the effect of
different scanners has to be taken into account. For longitudinal
monocentric studies, the expected effect size should exceed the size of
false positive findings observed in this study. Assuming a physiological
loss of brain volume of about 0.3% per year in healthy adult subjects
(Good et al., 2001), which may double in MS (De Stefano et al., 2010; De
Stefano et al., 2015), with current tools reliable estimation of brain
atrophy in individual patients is only possible over periods of several
years. (C) 2016 Elsevier Inc. All rights reserved.
