title: Test-Retest Reliability of Diffusion Tensor Imaging in Huntington's Disease.
abstract: Diffusion tensor imaging (DTI) has shown microstructural abnormalities in patients with Huntington's Disease (HD) and work is underway to characterise how these abnormalities change with disease progression. Using methods that will be applied in longitudinal research, we sought to establish the reliability of DTI in early HD patients and controls. Test-retest reliability, quantified using the intraclass correlation coefficient (ICC), was assessed using region-of-interest (ROI)-based white matter atlas and voxelwise approaches on repeat scan data from 22 participants (10 early HD, 12 controls). T1 data was used to generate further ROIs for analysis in a reduced sample of 18 participants. The results suggest that fractional anisotropy (FA) and other diffusivity metrics are generally highly reliable, with ICCs indicating considerably lower within-subject compared to between-subject variability in both HD patients and controls. Where ICC was low, particularly for the diffusivity measures in the caudate and putamen, this was partly influenced by outliers. The analysis suggests that the specific DTI methods used here are appropriate for cross-sectional research in HD, and give confidence that they can also be applied longitudinally, although this requires further investigation. An important caveat for DTI studies is that test-retest reliability may not be evenly distributed throughout the brain whereby highly anisotropic white matter regions tended to show lower relative within-subject variability than other white or grey matter regions.
authors.affiliation: Huntington's Disease Research Group, Department of Neurodegenerative Disease, UCL Institute of Neurology, London, UK; Computational, Cognitive & Clinical Neuroimaging Laboratory, Department of Medicine, Imperial College London, UK.
authors.forename: James H
authors.initials: JH
authors.lastname: Cole
authors.affiliation: Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Farmer
authors.affiliation: Huntington's Disease Research Group, Department of Neurodegenerative Disease, UCL Institute of Neurology, London, UK.
authors.forename: Elin M
authors.initials: EM
authors.lastname: Rees
authors.affiliation: Department of Psychiatry, University of Iowa, Iowa City, Iowa, USA.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Johnson
authors.affiliation: Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Frost
authors.affiliation: Huntington's Disease Research Group, Department of Neurodegenerative Disease, UCL Institute of Neurology, London, UK.
authors.forename: Rachael I
authors.initials: RI
authors.lastname: Scahill
authors.affiliation: Huntington's Disease Research Group, Department of Neurodegenerative Disease, UCL Institute of Neurology, London, UK.
authors.forename: Nicola Z
authors.initials: NZ
authors.lastname: Hobbs