Final answer:
PET scans have indeed shown that some individuals have increased cerebral blood flow in response to brain activity, as this method maps active areas by monitoring the flow of a radioactive tracer. They have proven useful in various medical and research applications but are now often replaced with functional MRI (fMRI) scans.
Step-by-step explanation:
True, positron emission tomography (PET) scans have shown that some individuals have increased cerebral blood flow. This imaging technique leverages a mildly radioactive tracer injected or consumed by the individual. As brain areas become more active, they require more blood, thus, more tracer is present in those areas. Using this approach, a PET scan can generate a map of active regions within the brain while performing certain behaviors or tasks.
PET scans serve multiple roles in medical diagnosis and research. They are particularly valuable for studying brain function and anatomy. For instance, PET scans help identify parts of the brain responsible for various functions, monitor metabolic activity related to conditions like Alzheimer's disease, and assess how the brain utilizes oxygen and water.
However, it's worth mentioning that an alternative imaging tool, the functional MRI (fMRI), has largely supplanted the use of PET scans. The fMRI scans also measure changes in blood flow, but with better temporal precision and without exposing the brain to radiation.