title: Evaluating multicenter DTI data in Huntington's disease on site specific effects: An ex post facto approach.
abstract: OBJECTIVE
  Assessment of the feasibility to average diffusion tensor imaging (DTI) metrics of MRI data acquired in the course of a multicenter study.
  
  
  METHODS
  Sixty-one early stage Huntington's disease patients and forty healthy controls were studied using four different MR scanners at four European sites with acquisition protocols as close as possible to a given standard protocol. The potential and feasibility of averaging data acquired at different sites was evaluated quantitatively by region-of-interest (ROI) based statistical comparisons of coefficients of variation (CV) across centers, as well as by testing for significant group-by-center differences on averaged fractional anisotropy (FA) values between patients and controls. In addition, a whole-brain based statistical between-group comparison was performed using FA maps.
  
  
  RESULTS
  The ex post facto statistical evaluation of CV and FA-values in a priori defined ROIs showed no differences between sites above chance indicating that data were not systematically biased by center specific factors.
  
  
  CONCLUSIONS
  Averaging FA-maps from DTI data acquired at different study sites and different MR scanner types does not appear to be systematically biased. A suitable recipe for testing on the possibility to pool multicenter DTI data is provided to permit averaging of DTI-derived metrics to differentiate patients from healthy controls at a larger scale.
authors.affiliation: Department of Neurology, University of Ulm, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Müller
authors.forename: Georg
authors.initials: G
authors.lastname: Grön
authors.forename: Reiner
authors.initials: R
authors.lastname: Sprengelmeyer
authors.forename: Jan
authors.initials: J
authors.lastname: Kassubek
authors.forename: Albert C
authors.initials: AC
authors.lastname: Ludolph
authors.forename: Nicola
authors.initials: N
authors.lastname: Hobbs
authors.forename: James
authors.initials: J
authors.lastname: Cole
authors.forename: Raymund A C
authors.initials: RA
authors.lastname: Roos
authors.forename: Alexandra
authors.initials: A
authors.lastname: Duerr
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Tabrizi
authors.forename: G Bernhard
authors.initials: GB
authors.lastname: Landwehrmeyer
authors.forename: Sigurd D
authors.initials: SD
authors.lastname: Süssmuth
keywords: Diffusion tensor imaging; Fractional anisotropy; Huntington's disease; Multicenter study