Joshi A, Pontecorvo M, Breault C, Lu M, Mintun M, Carpenter A, Skorvonsky D.
Use of Florbetapir-PET to Assess Progression of Amyloid Burden over Time.Human Amyloid Imaging Abstract.
2012 Jan 1;
Objective: To evaluate the change in beta-amyloid deposition in mild cognitive impairment (MCI) and cognitively normal elderly controls (CN) over-years of follow-up.
Method: subjects comprised of9 CNs (MMSE ≥9; age1±11) and6 MCI (CDR 0.5, MMSE >24; age1±10) underwent florbetapir-PET scans at baseline and approximately two years later (23±4 months). Scans were independently spatially normalized to a standard florbetapir PET template in Talairach space. Standard uptake value (SUVr) ratios were calculated using the mean of pre-defined anatomically relevant cortical regions ( precuneus, posterior cingulate, anterior cingulate, frontal, temporal and parietal), relative to entire cerebellum. The relationship between change in SUVr and baseline PET SUVr and diagnostic group was examined.
Results: SUVr values from baseline and follow-up scans were highly correlated (Pearson correlation, r=0.96). Using an SUVr cut-off of.10% (16/36) of MCI subjects and0 % (10/49) of CN subjects had scans at baseline that were considered positive for amyloid. The group of subjects that were positive at baseline (mean SUVr=.37) had a significant change in SUVr (mean delta= +0.06; p< 0.05) while the subjects that were negative at baseline (mean SUVr=0.98) did not (mean delta = +0.005; p=0.40). Interestingly, among the9 subjects that were amyloid negative at baseline, subjects (6.8%) had converted to amyloid positive on the follow-up scan for a conversion rate of.5 % per year. None of the subjects who were amyloid positive at baseline converted to amyloid negative on follow-up.
Conclusion: These florbetapir-PET results suggest non-demented subjects with evidence of beta-amyloid deposits have continued increase in amyloid. Those subjects without evidence of beta-amyloid show no mean increase at two years. However, a small number of subjects may convert from negative to positive during this time.