Positron Emission Tomography
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Single-Photon Emission Computer Tomography (SPECT) and Positron Emission Tomography (PET) use radioactive tracers which are taken up where blood flow is greater. SPECT and PET therefore provide images of blood flow (again, considered a sign of greater brain activity) in different parts of the brain. However, they do not provide as much anatomical detail as MRI or CT scans.
Scientists can choose what to look at by selecting a tracer that seeks out a particular set of receptors in the brain. For example, they can use I-benzamide, which likes to bind with D2 dopamine receptors, to gain a picture of the density of dopamine receptors, information which is useful in Parkinson's. Positron Emission Tomography can also be used for these receptor binding studies, and has been used to investigate D2 dopamine receptors, benzodiazepine recepts, seratonin receptors and opiate receptors.
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