Dual‐tracer assessment of CBF and early amyloid uptake of Alzheimer’s disease using 15O‐water and amyloid PET

Abstract Background Reduced CBF and amyloid update measured by PET imaging have been reported among Alzheimer’s disease (AD) patients. Evidence suggested that early amyloid update may reflect the underlying CBF information. In this pilot study, we aimed to compare whether early uptake amyloid PET images can be used to estimate CBF, by comparing them with gold‐standard 15O‐water PET CBF images. Method Data were collected from an AD patient (female, 74 years) and a normal subject (female, 75 years) using a simultaneous 3T PET/MRI system and injection of 775 MBq of 15O‐water followed by 330 MBq of the amyloid radiotracer 18F‐florbetaben. CBF was computed by fitting the reconstructed PET data to a one‐compartment pharmacokinetic model using an image‐derived AIF. The amyloid PET data were reconstructed from time of injection to 1 and 5 minutes post‐injection yielding two short early duration uptake images, with the OSEM reconstruction parameters set as 2 iterations, 28 subsets, and a 4mm Gaussian post‐reconstruction filter. All images were transformed to the MNI‐152 2mm standard space using non‐linear registration. Result The figure shows the measured CBF and amyloid PET maps of the patient and normal subject. In the AD patient, a CBF deficit is present in the posterior biparietal regions (indicated by the arrows), in contrast with other regions. This characteristic CBF deficit is not seen in the normal subject. Conclusion With further investigation and quantification in various tracers and participant populations, using early dynamic data acquired with amyloid PET tracers could be a potential tool for measuring CBF