title: Comparing 3T and 1.5T MRI for mapping hippocampal atrophy in the Alzheimer's Disease Neuroimaging Initiative.
abstract: OBJECTIVE
  Prior MR imaging studies, primarily at 1.5T, established hippocampal atrophy as a biomarker for Alzheimer disease. 3T MR imaging offers a higher contrast and signal-to-noise ratio, yet distortions and intensity uniformity are harder to control. We applied our automated hippocampal segmentation technique to 1.5T and 3T MR imaging data, to determine whether hippocampal atrophy detection was enhanced at 3T.
  
  
  METHODS
  We analyzed baseline MR imaging data from 166 subjects from the Alzheimer's Disease Neuroimaging Initiative-1 (37 with Alzheimer disease, 76 with mild cognitive impairment, and 53 healthy controls) scanned at 1.5T and 3T. Using multiple linear regression, we analyzed the effect of clinical diagnosis on hippocampal radial distance, while adjusting for sex. 3D statistical maps were adjusted for multiple comparisons by using permutation-based statistics at a threshold of P < .01.
  
  
  RESULTS
  Bilaterally significant radial distance differences in the areas corresponding to the cornu ammonis 1, cornu ammonis 2, and subiculum were detected for Alzheimer disease versus healthy controls and mild cognitive impairment versus healthy controls at 1.5T and more profoundly at 3T. Comparison of Alzheimer disease with mild cognitive impairment did not reveal significant differences at either field strength. Subjects who converted from mild cognitive impairment to Alzheimer disease within 3 years of the baseline scan versus nonconverters showed significant differences in the area corresponding to cornu ammonis 1 of the right hippocampus at 3T but not at 1.5T.
  
  
  CONCLUSIONS
  While hippocampal atrophy patterns in diagnostic comparisons were similar at 1.5T and 3T, 3T showed a superior signal-to-noise ratio and detected atrophy with greater effect size compared with 1.5T.
authors.affiliation: From the School of Medicine (N.C.), University of California, Irvine, Irvine, California.
authors.forename: N
authors.initials: N
authors.lastname: Chow
authors.affiliation: Oakland University William Beaumont School of Medicine (K.S.H.), Rochester Hills, Michigan Departments of Neurology (K.S.H., S.H., L.G.A.).
authors.forename: K S
authors.initials: KS
authors.lastname: Hwang
authors.affiliation: Departments of Neurology (K.S.H., S.H., L.G.A.).
authors.forename: S
authors.initials: S
authors.lastname: Hurtz
authors.affiliation: Department of Physiology (A.E.G.), Monash University, Melbourne, Australia.
authors.forename: A E
authors.initials: AE
authors.lastname: Green
authors.affiliation: Department of Neurology (J.H.S.), Cruces University Hospital, Barakaldo, Spain.
authors.forename: J H
authors.initials: JH
authors.lastname: Somme
authors.affiliation: Imaging Genetics Center (P.M.T.), Institute for Neuroimaging and Informatics, Keck/University of Southern California School of Medicine, Los Angeles, California Departments of Neurology, Psychiatry, Engineering, Radiology, and Ophthalmology (P.M.T.), University of Southern California, Los Angeles, California.
authors.forename: P M
authors.initials: PM
authors.lastname: Thompson
authors.affiliation: Biostatistics (D.A.E.), University of California, Los Angeles, David Geffen School of Medicine, Los Angeles, California.
authors.forename: D A
authors.initials: DA
authors.lastname: Elashoff
authors.affiliation: Department of Radiology (C.R.J.), Mayo Clinic and Foundation, Rochester, Minnesota.
authors.forename: C R
authors.initials: CR
authors.lastname: Jack
authors.affiliation: Department of Radiology and Biomedical Imaging (M.W.), University of California, San Francisco, School of Medicine, San Francisco, California.
authors.forename: M
authors.initials: M
authors.lastname: Weiner
authors.affiliation: Departments of Neurology (K.S.H., S.H., L.G.A.) lapostolova@mednet.ucla.edu.
authors.forename: L G
authors.initials: LG
authors.lastname: Apostolova
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000473:pathology*; D001284:Atrophy / Q000473:pathology; D060825:Cognitive Dysfunction / Q000473:pathology; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D059906:Neuroimaging / Q000379:methods*