Question: what is the main advantage of carbon-11 compared to fluorine-18 for pet imaging studies

title: Positron emission tomography
text: PET scan of the human brain Neurology : PET neuroimaging is based on an assumption that areas of high radioactivity are associated with brain activity . What is actually measured indirectly is the flow of blood to different parts of the brain , which is , in general , believed to be correlated , and has been measured using the tracer oxygen - 15 . Because of its 2 - minute half - life , O - 15 must be piped directly from a medical cyclotron for such uses , which is difficult . In practice , since the brain is normally a rapid user of glucose , and since brain pathologies such as Alzheimer 's disease greatly decrease brain metabolism of both glucose and oxygen in tandem , standard FDG - PET of the brain , which measures regional glucose use , may also be successfully used to differentiate Alzheimer 's disease from other dementing processes , and also to make early diagnoses of Alzheimer 's disease . The advantage of FDG - PET for these uses is its much wider availability . PET imaging with FDG can also be used for localization of seizure focus : A seizure focus will appear as hypometabolic during an interictal scan . Several radiotracers ( i.e. radioligands ) have been developed for PET that are ligands for specific neuroreceptor subtypes such as ( C ) raclopride , ( F ) fallypride and ( F ) desmethoxyfallypride for dopamine D2 / D3 receptors , ( C ) McN 5652 and ( C ) DASB for serotonin transporters , ( F ) Mefway for serotonin 5HT1A receptors , ( F ) Nifene for nicotinic acetylcholine receptors or enzyme substrates ( e.g. 6 - FDOPA for the AADC enzyme ) . These agents permit the visualization of neuroreceptor pools in the context of a plurality of neuropsychiatric and neurologic illnesses .