title: In vivo detection of microstructural correlates of brain pathology in preclinical and early Alzheimer Disease with magnetic resonance imaging.
abstract: Alzheimer disease (AD) affects at least 5 million individuals in the USA alone stimulating an intense search for disease prevention and treatment therapies as well as for diagnostic techniques allowing early identification of AD during a long pre-symptomatic period that can be used for the initiation of prevention trials of disease-modifying therapies in asymptomatic individuals.
  
  
  
  Our approach to developing such techniques is based on the Gradient Echo Plural Contrast Imaging (GEPCI) technique that provides quantitative in vivo measurements of several brain-tissue-specific characteristics of the gradient echo MRI signal (GEPCI metrics) that depend on the integrity of brain tissue cellular structure. Preliminary data were obtained from 34 participants selected from the studies of aging and dementia at the Knight Alzheimer's Disease Research Center at Washington University in St. Louis. Cognitive status was operationalized with the Clinical Dementia Rating (CDR) scale. The participants, assessed as cognitively normal (CDR=0; n=23) or with mild AD dementia (CDR=0.5 or 1; n=11) underwent GEPCI MRI, a collection of cognitive performance tests and CSF amyloid (Aβ) biomarker Aβ42. A subset of 19 participants also underwent PET PiB studies to assess their brain Aβ burden. According to the Aβ status, cognitively normal participants were divided into normal (Aβ negative; n=13) and preclinical (Aβ positive; n=10) groups.
  
  
  
  GEPCI quantitative measurements demonstrated significant differences between all the groups: normal and preclinical, normal and mild AD, and preclinical and mild AD. GEPCI quantitative metrics characterizing tissue cellular integrity in the hippocampus demonstrated much stronger correlations with psychometric tests than the hippocampal atrophy. Importantly, GEPCI-determined changes in the hippocampal tissue cellular integrity were detected even in the hippocampal areas not affected by the atrophy. Our studies also uncovered strong correlations between GEPCI brain tissue metrics and beta-amyloid (Aβ) burden defined by positron emission tomography (PET) - the current in vivo gold standard for detection of cortical Aβ, thus supporting GEPCI as a potential surrogate marker for Aβ imaging - a known biomarker of early AD. Remarkably, the data show significant correlations not only in the areas of high Aβ accumulation (e.g. precuneus) but also in some areas of medial temporal lobe (e.g. parahippocampal cortex), where Aβ accumulation is relatively low.
  
  
  
  We have demonstrated that GEPCI provides a new approach for the in vivo evaluation of AD-related tissue pathology in the preclinical and early symptomatic stages of AD. Since MRI is a widely available technology, the GEPCI surrogate markers of AD pathology have a potential for improving the quality of AD diagnostic, and the evaluation of new disease-modifying therapies.
authors.affiliation: Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Neurology, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Marcus E
authors.initials: ME
authors.lastname: Raichle
authors.affiliation: Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Wen
authors.affiliation: Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Tammie L
authors.initials: TL
authors.lastname: Benzinger
authors.affiliation: Department of Neurology, Washington University in St. Louis, St. Louis, MO 63110, USA; Knight Alzheimer's Disease Research Center, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Fagan
authors.affiliation: Department of Neurology, Washington University in St. Louis, St. Louis, MO 63110, USA; Knight Alzheimer's Disease Research Center, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Hassenstab
authors.affiliation: Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Andrei G
authors.initials: AG
authors.lastname: Vlassenko
authors.affiliation: Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Neurology, Washington University in St. Louis, St. Louis, MO 63110, USA; Knight Alzheimer's Disease Research Center, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Cairns
authors.affiliation: Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Jon J
authors.initials: JJ
authors.lastname: Christensen
authors.affiliation: Department of Neurology, Washington University in St. Louis, St. Louis, MO 63110, USA; Knight Alzheimer's Disease Research Center, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Morris
authors.affiliation: Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA. Electronic address: yablonskiyd@wustl.edu.
authors.forename: Dmitriy A
authors.initials: DA
authors.lastname: Yablonskiy
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000000981:diagnostic imaging* / Q000473:pathology*; D016229:Amyloid beta-Peptides / Q000378:metabolism; D001284:Atrophy; D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology*; D060825:Cognitive Dysfunction / Q000000981:diagnostic imaging / Q000473:pathology; D018450:Disease Progression; D017352:Echo-Planar Imaging; D005260:Female; D006624:Hippocampus / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D020534:Parahippocampal Gyrus / Q000000981:diagnostic imaging / Q000473:pathology; D049268:Positron-Emission Tomography; D062706:Prodromal Symptoms; D012016:Reference Values
chemical_list: D016229:Amyloid beta-Peptides
keywords: Alzheimer's disease; Beta-amyloid; GEPCI; MRI; PET; Pathology