title: Fractional anisotropy derived from the diffusion tensor distribution function boosts power to detect Alzheimer's disease deficits.
abstract: OBJECTIVE
  In diffusion MRI (dMRI), fractional anisotropy derived from the single-tensor model (FADTI) is the most widely used metric to characterize white matter (WM) microarchitecture, despite known limitations in regions with crossing fibers. Due to time constraints when scanning patients in clinical settings, high angular resolution diffusion imaging acquisition protocols, often used to overcome these limitations, are still rare in clinical population studies. However, the tensor distribution function (TDF) may be used to model multiple underlying fibers by representing the diffusion profile as a probabilistic mixture of tensors.
  
  
  METHODS
  We compared the ability of standard FADTIand TDF-derived FA (FATDF), calculated from a range of dMRI angular resolutions (41, 30, 15, and 7 gradient directions), to profile WM deficits in 251 individuals from the Alzheimer's Disease Neuroimaging Initiative and to detect associations with 1) Alzheimer's disease diagnosis, 2) Clinical Dementia Rating scores, and 3) average hippocampal volume.
  
  
  RESULTS
  Across angular resolutions and statistical tests, FATDFshowed larger effect sizes than FADTI, particularly in regions preferentially affected by Alzheimer's disease, and was less susceptible to crossing fiber anomalies.
  
  
  CONCLUSIONS
  The TDF "corrected" form of FA may be a more sensitive and accurate alternative to the commonly used FADTI, even in clinical quality dMRI data. Magn Reson Med 78:2322-2333, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Imaging Genetics Center, University of Southern California, Marina del Rey, California, USA.
authors.forename: Talia M
authors.initials: TM
authors.lastname: Nir
authors.affiliation: Imaging Genetics Center, University of Southern California, Marina del Rey, California, USA.
authors.forename: Neda
authors.initials: N
authors.lastname: Jahanshad
authors.affiliation: Imaging Genetics Center, University of Southern California, Marina del Rey, California, USA.
authors.forename: Julio E
authors.initials: JE
authors.lastname: Villalon-Reina
authors.affiliation: Imaging Genetics Center, University of Southern California, Marina del Rey, California, USA.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Isaev
authors.affiliation: Imaging Genetics Center, University of Southern California, Marina del Rey, California, USA.
authors.forename: Artemis
authors.initials: A
authors.lastname: Zavaliangos-Petropulu
authors.affiliation: Computer Engineering Program, University of Wisconsin-Stout, Menomonie, Wisconsin, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhan
authors.affiliation: Department of Psychiatry and Bioengineering, University of Illinois, Chicago, Illinois, USA.
authors.forename: Alex D
authors.initials: AD
authors.lastname: Leow
authors.affiliation: Department of Radiology, Mayo Clinic and Foundation, Rochester, Minnesota, USA.
authors.forename: Clifford R
authors.initials: CR
authors.lastname: Jack
authors.affiliation: Department of Radiology, University of California San Francisco School of Medicine, San Francisco, California, USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Weiner
authors.affiliation: Imaging Genetics Center, University of Southern California, Marina del Rey, California, USA.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Thompson
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000000981:diagnostic imaging*; D016880:Anisotropy; D001921:Brain / Q000000981:diagnostic imaging; D001931:Brain Mapping; D003072:Cognition Disorders / Q000000981:diagnostic imaging; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006624:Hippocampus / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008137:Longitudinal Studies; D008297:Male; D008568:Memory; D008569:Memory Disorders / Q000000981:diagnostic imaging; D008875:Middle Aged; D015203:Reproducibility of Results; D066127:White Matter / Q000000981:diagnostic imaging
keywords: Alzheimer's disease; diffusion-weighted imaging; fractional anisotropy; tensor distribution function; white matter