(Positron Emission Tomography) is a new method of scanning which is helpful in the diagnosis of epilepsy.The principle of PET scanning is to see which parts of the brain are active, either by measuring the blood flow through different parts of the brain, or by seeing how actively the different areas of the brain are metabolizing a substance, usually sugar.To do this, an injection of radioactively-labelled glucose or a dose of radioactively-labelled oxygen in water is given. The radioactivity is taken up more readily by the active areas of the brain. As the radioactivity decays, the PET scanner detects the decay products and calculates where the radioactivity has come from within the brain. The scanner then makes a map of the brain showing the active and inactive metabolic areas. It has been found that areas of the brain which have an active epileptic focus are metabolically less active between seizures, as if the brain were trying to stop the spread of epileptic activity. Not surprisingly, during a seizure this area becomes more active than the surrounding brain. PET scanning is therefore able to give some idea of where seizures are arising.SPECT or SPET (Single Photon Emission Computer Tomography or Single Photon Emission Tomography) is a less accurate scanning method essentially the same as PET but using a different radioactive chemical which is easier to use. This has the advantage that it can be given during a seizure.*22\193\2*
