Abstract
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Objectives Examine yearly PiB retention relative to clinical covariates of Alzheimer’s disease in 25 control (CN) (70±10 yr, MMSE 29±1) and 10 mild cognitive impairment (MCI) (70±7 yr, MMSE 28±1) subjects at 1 year and 20 CN (75±9 yr, MMSE 29±1) and 4 MCI (70±6 yr, MMSE 28±1) subjects at 2 years.
Methods PiB PET data (HR+, 15 mCi, 90 min) were collected over 2 years. MRI was used for region definition and atrophy correction. Yearly changes in Logan distribution volume ratio measures (DVR, cerebellum reference) of PiB retention were computed: DIFFyr = DVRyr – DVRbase. Partial least squares (PLS) was applied to covariates (PiB+/-, age, MMSE, APOE status, yrs of education: Ed) and yearly PiB DVRs (9 areas: global mean [Gm: cingulate ACG, precuneus PRC, frontal FRC, temporal LTC, parietal PAR, striatum AVS] and 3 white matter rich areas). A PLS latent variable (LV) weight ≥0.3 was empirical indicator of important variable.
Results Gm DIFFyr for year 1 was 0.04±0.07 for CNs (3%) and 0.06±0.12 for MCIs (4%) and at year 2 was 0.06±0.10 for CNs (4%) and 0.10±0.12 for MCIs (5%). A PLS analysis applied to a subset scanned at each time (12CN, 4MCI) yielded 1 component (>96% variation explained). The covariates more related to the LV were Ed (0.7), PiB+/- (0.6) for year 1 and PiB+/- (0.8), MMSE (0.5) for year 2. PiB DVRs for global areas were related (0.3-0.4) to Ed and PIB+/- (year 1) and PIB+/- and MMSE (year 2).
Conclusions Yearly changes were greater for MCIs than controls. PiB DVR values were related to clinical variables with Ed most strongly related at year 1 and MMSE at year 2.
Research Support NIH, Dana Foundation, Alzheimer’s Association
- © 2009 by Society of Nuclear Medicine