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PET (Positron Emission Tomography) is a safe, effective and non-invasive diagnostic imaging technique. It provides images that show chemical and functional changes within the brain. PET is very sensitive and it can detect changes in the brain associated with seeing, hearing and thinking. Similarly, it can detect changes in the brain associated with certain diseases that cannot be seen with other imaging methods.
For example, in patients with epilepsy, it can show which part of the brain is responsible for the seizures, even if the patient had a normal MR or CT of the brain. Another example: in patients who have been treated for brain tumors, PET helps define if the tumor is still growing or is inactive.
PET of the brain is obtained after the intravenous injection of a radiotracer (also called radiopharmaceutical). The most commonly used PET brain radiopharmaceutical is a substance similar to sugar or glucose and it is called fluorodeoxyglucose (FDG), which is labeled with a radioisotope called fluorine-18 (18F). This radioisotope has a short physical half-life (T1/2 = 111 minutes). For short, this radiopharmaceutical is called 18F-FDG.
Once injected, FDG rapidly (30-40 minutes) localizes in the brain. The brain consumes large amounts of glucose and FDG will localize on the corresponding regions of the brain. Once FDG is in the brain, images are obtained using an imaging device called a PET scanner. The PET scanner obtains 3-D images of glucose in the brain that helps physicians diagnose certain disorders.
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