Can relative flow derived from dynamic 11C-PIB scans replace FDG scans in Alzheimer disease PET studies?

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Aim: Different PET biomarkers are used for the differential diagnosis of neurodegenerative diseases such as Alzheimer’s disease (AD). β-amyloid plaque deposition can be assessed by 11C-Pittsburgh Compound B (PIB) while 18F-fluorodeoxyglucose (FDG) is used to assess cerebral glucose metabolism, which can be an indicator for synaptic dysfunction. Although FDG is a biomarker for glucose consumption, its distribution is strongly affected by cerebral perfusion. The aim of the study is to explore whether relative blood flow (rCBF) data, extracted from dynamic 11C-PIB studies, can be used as a surrogate for relative FDG distributions. Methods: Thirty subjects (10 AD, 10 mild cognitive impairment (MCI) patients, and 10 healthy controls (HC)) underwent static 18F-FDG (45-60 min p.i.) and 70 min dynamic 11C-PIB PET scans. T1-MRI scans were used for anatomical labelling of brain regions. Parametric 11C-PIB rCBF images (R1: tracer delivery relative to the cerebellum) were obtained using the simplified reference tissue model 2 (SRTM2, PMOD v3.8). 18F-FDG images were normalized to the cerebellar grey matter values (SUVr). The Hammers atlas was used to analyze regional correlations between R1 and SUVr. We used SPM12 to compare SUVr and R1 statistical parametric maps between AD and HC. Results: The regional analysis showed strong correlations between R1 and SUVr for AD, MCI and HC (group average R2 of 0.89 (AD), 0.90 (MCI) and 0.84 (HC)). Both R1 and SUVr showed similar statistical parametric maps for AD and HC which are in agreement with previous reports in literature. However, SPM based on R1 showed a smaller number of significant clusters involved than with the SPM based on FDG SUVr. In addition, the clusters found in R1 were smaller in size and T-value. For example, in the left inferiolateral parietal lobe FDG SUVr showed 2297 voxels(mean(T)=5.4) versus 999 voxels for R1 (mean(T)=4.7). Conclusion: Relative cerebral perfusion images (R1) obtained from 11C-PIB dynamic PET acquisitions are strongly correlated with normalized 18F-FDG images in all 3 groups and largely show the same SPM pattern in a group comparison. However, the observed group differences for R1 were smaller and less significant which may be related to the lower signal-to-noise ratio of the R1 images. These preliminary results suggest that dynamic 11C-PIB PET can not only be used to assess β-amyloid plaque deposition, but that relative rCBF derived from these scans can in some cases be used to replace FDG thereby obviating the need to perform a second tracer (FDG) study.
Original languageEnglish
Pages (from-to)S419-S420
JournalEuropean Journal of Nuclear Medicine and Molecular Imaging
Issue numberSuppl 2
Publication statusPublished - 6-Oct-2017
Event30th Annual Congress of the European Association of Nuclear Medicine (EANM) - Vienna, Austria
Duration: 21-Oct-201725-Oct-2017
Conference number: 30

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