[Benzodiazepine receptor imaging with positron emission tomography and single photon emission tomography]

11C-Flumazenil and 123I-iomazenil are PET and SPECT ligands that bind with high affinity and selectivity to central benzodiazepine receptors. These radiopharmaceuticals are highly suitable for the localization of epileptogenic foci in partial epilepsy. With 11C-flumazenil it is possible to localize epileptogenic foci more accurately than with 18FDG. This PET ligand is also superior to the SPECT ligand and therefore with its increased availability it will possibly become more important in the presurgical assessment of patients with medically intractable temporal and especially extratemporal lobe epilepsy. Due to the high amount of cortical GABAergic synapses, 11C-flumazenil and 123I-iomazenil seem suitable as markers for the integrity of neuronal structure. With the help of these ligands, functionally disturbed areas of the brain can be differentiated from structural changes in patients with cerebral infarcts, cortical dysplasias, traumatic brain lesions or systemic degeneration. Another potential field of clinical use could be the individual pharmacological monitoring of drugs interacting with the GABAA-receptor complex. Imaging of the peripheral-type benzodiazepine receptor seems to be exclusively of scientific interest.