Cerebral blood flow and metabolism are generally interconnected. Alterations in brain function are associated with corresponding changes in perfusion. Radionuclide brain perfusion studies using lipophilic tracers are useful in the study of abnormalities of regional perfusion such as stroke and in the evaluation of changes related to neuronal activity like epilepsy and trauma. Their use in psychiatric conditions is promising. Several radiopharmaceuticals are used for imaging central nervous system. These include 99mTc-HMPAO (Fig. 9.1), PET tracers such as F-18 FDG, amyloid-binding radiotracers, tau-PET tracers, and less commonly In-111 DTPA. Additionally, somatostatin receptor imaging with DOTATATE-PET in meningioma and dopamine transporter imaging with DaT scans in parkinsonian syndromes are also included.