title: Multi-site Study of Diffusion Metric Variability: Characterizing the Effects of Site, Vendor, Field Strength, and Echo Time using the Histogram Distance.
abstract: MRI-based multi-site trials now routinely include some form of diffusion-weighted imaging (DWI) in their protocol. These studies can include data originating from scanners built by different vendors, each with their own set of unique protocol restrictions, including restrictions on the number of available gradient directions, whether an externally-generated list of gradient directions can be used, and restrictions on the echo time (TE). One challenge of multi-site studies is to create a common imaging protocol that will result in a reliable and accurate set of diffusion metrics. The present study describes the effect of site, scanner vendor, field strength, and TE on two common metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA). We have shown in earlier work that ROI metrics and the mean of MD and FA histograms are not sufficiently sensitive for use in site characterization. Here we use the distance between whole brain histograms of FA and MD to investigate within- and between-site effects. We concluded that the variability of DTI metrics due to site, vendor, field strength, and echo time could influence the results in multi-center trials and that histogram distance is sensitive metrics for each of these variables.
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA; Department of Radiology, Massachusetts General Hospital, Boston, MA; Harvard Medical School, Boston, MA.
authors.forename: K G
authors.initials: KG
authors.lastname: Helmer
authors.affiliation: Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: M-C
authors.initials: MC
authors.lastname: Chou
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA.
authors.forename: R I
authors.initials: RI
authors.lastname: Preciado
authors.affiliation: The Geisel School of Medicine at Dartmouth, Hanover, NH.
authors.forename: B
authors.initials: B
authors.lastname: Gimi
authors.affiliation: Univ. of Texas, Southwestern Medical Center at Dallas, Radiology, Dallas TX.
authors.forename: N K
authors.initials: NK
authors.lastname: Rollins
authors.affiliation: Brain Imaging and Analysis Center, Duke University School of Medicine, Durham, NC.
authors.forename: A
authors.initials: A
authors.lastname: Song
authors.affiliation: The MIND Research Network, Albuquerque, NM.
authors.forename: J
authors.initials: J
authors.lastname: Turner
authors.affiliation: Johns Hopkins University School of Medicine, Baltimore, MD.
authors.forename: S
authors.initials: S
authors.lastname: Mori
keywords: MRI; calibration; diffusion; histogram distance; multi-site study