Single-photon Emission Tomography SPET Principle uses single-photon (gamma-ray) emitting isotopes given IV or inhaled the resolution is lower than PET Uses SPET can give information about: regional cerebral blood flow ligand binding Clinical uses include: Alzheimer’s disease When the symptomatology (e.g. hallucinations, epilepsy) occurs when the patient is not near a scanner; we can give a suitable ligand at the material time and the patient scanned afterward Schizophrenia reduced rCBF in frontal regions—‘hypofrontality’ Affective disorders as that in schizophrenia, with reversal after antidepressant therapy Alzheimer’s disease decreased rCBF in posterior parietal and temporal regions Xenon inhalation Shows the failure of activation of frontal lobes in schizophrenics performing the Wisconsin Card Sorting Test