Abstract
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Objectives: Subcortical white matter (SWM) is known to be relatively unaffected by amyloid deposition in Alzheimer’s disease (AD). This study investigates the feasibility of using SWM as a reference region to quantify [18F]FDDNP binding in human brain.
Methods: Imaging studies were performed on 8 AD and 5 normal control subjects. Dynamic PET scans were acquired for 125 min with an ECAT HR+ in 3D mode following ~10 mCi bolus injection of tracer. A head movement correction procedure (IEEE-MIC 2007;3974-3977) was applied prior to defining regions of interest on the summed image of early frames. Regions included centrum semiovale for SWM, posterior cingulate, frontal, parietal, medial temporal, and lateral temporal cortices, whose time-activity curves (TACs) were extracted from the dynamic PET data. Population efflux rate constant (k’2) in SWM was derived by a modeling approach (IEEE-MIC 2007;3147-3150). Logan graphical analysis was applied to regional TACs to estimate the distribution volume ratio (DVR) using the SWM as the reference region.
Results: The population estimates of k’2 in SWM were 0.024±0.004 min-1 and 0.022±0.004 min-1 for control and AD groups, respectively, and did not differ significantly. The DVR estimates in posterior cingulate, frontal, parietal, and temporal cortices were significantly higher in AD group (P < 0.02). The results agreed well with those derived using cerebellum as the reference input (NEJM 2006;355:2652-2663).
Conclusions: Subcortical white matter can be used as a reference region for quantitative analysis of [18F]FDDNP but a population k’2 has to be determined a priori.
Research Support: DOE contract DE-FG02-02ER63420; NIH grant P01-AG024831
- Society of Nuclear Medicine, Inc.