In Alzheimer’s Disease (AD) dual-tracer positron emission tomography (PET) studies with 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) and 11C-labelled Pittsburgh Compound B (PIB) are used to assess metabolism and cerebral amyloid-β deposition, respectively. Regional cerebral metabolism and blood flow (rCBF) are closely coupled, both providing an index for neuronal function. The present study compared PIB-derived rCBF, estimated by the ratio of tracer influx in target regions relative to reference region (R1) and early-stage PIB uptake (ePIB), to FDG scans. Fifteen PIB positive (+) patients and fifteen PIB negative (-) subjects underwent both FDG and PIB PET scans to assess the use of R1 and ePIB as a surrogate for FDG. First, subjects were classified based on visual inspection of the PIB PET images. Then, discriminative performance (PIB+ versus PIB-) of rCBF methods were compared to normalized regional FDG uptake. Strong positive correlations were found between analyses, suggesting that PIB-derived rCBF provides information that is closely related to what can be seen on FDG scans. Yet group related differences between method’s distributions were seen as well. Also, a better correlation with FDG was found for R1 than for ePIB. Further studies are needed to validate the use of R1 as an alternative for FDG studies in clinical applications.

Background In clinical practice, visual assessment of glucose metabolism images is often used for the diagnosis of Alzheimer’s disease (AD) through 2-[ 18 F]-fluoro-2-deoxy- d -glucose (FDG) positron emission tomography (PET) scans. However, visual assessment of the characteristic AD hypometabolic pattern relies on the expertise of the reader. Therefore, user-independent pipelines are preferred to evaluate the images and to classify the subjects. Moreover, glucose consumption is highly correlated with cerebral perfusion. Regional cerebral blood flow (rCBF) images can be derived from dynamic 11 C-labelled Pittsburgh Compound B PET scans, which are also used for the assessment of the deposition of amyloid-β plaques on the brain, a fundamental characteristic of AD. The aim of this study was to explore whether these rCBF PIB images could be used for diagnostic purposes through the PMOD Alzheimer’s Discrimination Tool. Results Both tracer relative cerebral flow ( R 1 ) and early PIB (ePIB) (20–130 s) uptake presented a good correlation when compared to FDG standardized uptake value ratio (SUVR), while ePIB (1–8 min) showed a worse correlation. All receiver operating characteristic curves exhibited a similar shape, with high area under the curve values, and no statistically significant differences were found between curves. However, R 1 and ePIB (1–8 min) had the highest sensitivity, while FDG SUVR had the highest specificity. Conclusion rCBF images were suggested to be a good surrogate for FDG scans for diagnostic purposes considering an adjusted threshold value. Electronic supplementary material The online version of this article (10.1186/s13550-019-0528-3) contains supplementary material, which is available to authorized users.

This suggests that CCD might be caused by non-amyloid neurodegeneration. The pathophysiological mechanism, clinical relevance and therapeutic implications of CCD and the role of the cerebellum in AD need further investigation.