What is fMRI?

Functional MRI (fMRI) is cheaper, simpler and more sensitive than PET scanning, and does not use radioactivity. For an fMRI scan, the person lies inside a huge magnet - as strong as the ones used to pick up scrap cars. fMRI shows up areas of the brain with an increased oxygen supply (more active brain tissue uses more oxygen). It relies on the fact that molecules in blood cells respond differently to magnets depending on how much oxygen they are carrying.

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An fMRI scan of the brain, showing hearing and seeing areas.

What is PET?

Scientists have used PET to investigate what different areas of the brain do, how the brain develops and how drugs affect it. The information gathered from PET scans can be added to MRI images from the same person - this provides a better idea of exactly where the activity is taking place. PET scans can detect changes due to brain damage, epilepsy, Alzheimer's disease and brain tumours, often earlier than is possible using other methods. But PET is an expensive and time-consuming technique.

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PET scan of an Alzheimer disease brain (right) and normal brain (left).

How does PET work?

A PET scan detects radioactively labelled molecules (such as oxygen or glucose), which will be used by active neurons in the brain. The radioactive substance is injected into the patient's blood where it gives off positrons, which break down to produce gamma rays. A gamma ray detector traces the flow of blood around the body.

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A PET scanner.

 

Principal Funder:

Wellcome trust

Major Sponsors:

GlaxoSmithKline life technologies