Disease Neuroimaging Initiative Hippocampal Atrophy in the Alzheimer's Comparing 3T and 1.5T MRI for Mapping

BACKGROUNDANDPURPOSE: PriorMRimagingstudies,primarilyat1.5T,establishedhippocampalatrophyasabiomarkerforAlzheimer disease. 3T MR imaging offers a higher contrast and signal-to-noise ratio, yet distortions and intensity uniformity are harder to control. We appliedourautomatedhippocampalsegmentationtechniqueto1.5Tand3TMRimagingdata,todeterminewhetherhippocampalatrophy detection was enhanced at 3T. MATERIALS AND 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 (cid:2) .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 nonconvertersshowedsignificantdifferencesintheareacorrespondingtocornuammonis1oftherighthippocampusat3Tbutnotat1.5T. 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.