What are the normal patterns of radiotracer uptake for CBF SPECT and FDG PET scans?
In most cases, CBF and glucose metabolism correlate or are coupled. Therefore, the pattern of CBF and cerebral metabolism should appear similar. Generally, brain scans should demonstrate uniform and symmetric radiotracer uptake throughout the brain. There should be no cortical defects. The subcortical structures sometimes appear to have slightly higher radiotracer activity compared to the cortex. The temporal lobes can appear slightly reduced due to their location and being surrounded by bone. The cerebellum typically appears more active relative to the cortex in CBF-SPECT scans and of similar activity on FDG PET scans. With normal aging, there can be mild decreases in cortical activity, particularly in the frontal lobes.