Reduced fractional anisotropy in ageing: Is it driven by changes in tissue microstructure or by partial volume effects?
Johan Westborg 1 , Danielle Van Westen 1,2 , Markus Nilsson 3 , Jimmy Ltt 2 , Filip Szczepankiewicz 4 , Sebastian Palmqvist 5 , Erik Stomrud 5 , Lennart Minthon 5 , Katarina Ngga 5 , and Oskar Hansson 5
Department of Diagnostic Radiology, Lund
University, Lund, Sweden,
for Medical Imaging and Physiology, Skane University
Hospital, Lund, Sweden,
University Bioimaging Center, Lund University, Lund,
of Medical Radiation Physics, Lund University, Lund,
Clinical Memory Research Unit,
Clinical Sciences, Lund University, Malm, Sweden
Our aim was to disentangle the contribution of
microstructural change and partial volume effects (PVE)
to the reduction of the fractional anisotropy (FA) in
the corpus callosum, observed in ageing. Using
tractography, we show that the FA reduction with age
becomes non-significant when the voxel-count in the
tract segments is corrected for. An observed FA
reduction in older (>71 years) subjects with ventricular
enlargement was primarily driven by increased callosal
atrophy. We did not observe microstructural change
separate from atrophy and increased PVE.
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