title: Longitudinal progression of cognitive decline correlates with changes in the spatial pattern of brain 18F-FDG PET.
abstract: Evaluating the symptomatic progression of mild cognitive impairment (MCI) caused by Alzheimer disease (AD) is practically accomplished by tracking performance on cognitive tasks, such as the Alzheimer Disease Assessment Scale's cognitive subscale (ADAS_cog), the Mini-Mental Status Examination (MMSE), and the Functional Activities Questionnaire (FAQ). The longitudinal relationships between cognitive decline and metabolic function as assessed using (18)F-FDG PET are needed to address both the cognitive and the biologic progression of disease state in individual subjects. We conducted an exploratory investigation to evaluate longitudinal changes in brain glucose metabolism of individual subjects and their relationship to the subject's changes of cognitive status.
  
  
  METHODS
  We describe a method to determine correlations in (18)F-FDG spatial distribution over time. This parameter is termed the regional (18)F-FDG time correlation coefficient (rFTC). By using linear mixed-effects models, we determined the difference in the rFTC decline rate between controls and subjects at high risk of developing AD, such as individuals with MCI or the presence of apolipoprotein E (APOE)-ε4 allele. The association between each subject's rFTC and performance on cognitive tests (ADAS_cog, MMSE, and FAQ) was determined with 2 different correlation methods. All subject data were downloaded from the Alzheimer Disease Neuroimaging Initiative.
  
  
  RESULTS
  The rFTC values of controls remained fairly constant over time (-0.003 annual change; 95% confidence interval, -0.010-0.004). In MCI patients, the rFTC declined faster than in controls by an additional annual change of -0.02 (95% confidence interval, -0.030 to -0.010). In MCI patients, the decline in rFTC was associated with cognitive decline (ADAS_cog, P = 0.011; FAQ, P = 0.0016; MMSE, P = 0.004). After a linear effect of time was accounted for, visit-to-visit changes in rFTC correlated with visit-to-visit changes in all 3 cognitive tests.
  
  
  CONCLUSIONS
  Longitudinal changes in rFTC detect subtle metabolic changes in individuals associated with variations in their cognition. This analytic tool may be useful for a patient-based monitoring of cognitive decline.
authors.affiliation: Department of Radiology and Radiological Sciences, Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA. sepideh.shokouhi@vanderbilt.edu
authors.forename: Sepideh
authors.initials: S
authors.lastname: Shokouhi
authors.forename: Daniel
authors.initials: D
authors.lastname: Claassen
authors.forename: Hakmook
authors.initials: H
authors.lastname: Kang
authors.forename: Zhaohua
authors.initials: Z
authors.lastname: Ding
authors.forename: Baxter
authors.initials: B
authors.lastname: Rogers
authors.forename: Arabinda
authors.initials: A
authors.lastname: Mishra
authors.forename: William R
authors.initials: WR
authors.lastname: Riddle
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism; D001921:Brain / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D060825:Cognitive Dysfunction / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D062211:Spatio-Temporal Analysis
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: 18F-FDG PET; 18F-FDG time correlation; Alzheimer imaging; longitudinal 18F-FDG imaging; mild cognitive impairment