Functional MRI (fMRI)

Functional MRI is performed on the same type of scanner as a regular MRI, but it focuses on brain function instead of anatomy. The patient lies inside the tunnel-shaped scanner and is asked to carry out simple tasks, such as tapping their fingers, looking at images or silently forming words. As the brain works, the scanner records where activity rises. The result is a detailed map of the brain that highlights the regions responsible for key functions, overlaid on a standard anatomical image so doctors can see exactly where these areas sit.

When part of the brain becomes more active, it needs more oxygen, and blood flow to that region briefly increases. Oxygen-rich and oxygen-poor blood behave slightly differently in a magnetic field, and the scanner is sensitive enough to detect this small difference. By repeating the measurement while the person rests and then performs a task, the computer works out which areas lit up during the activity. No injection or radiation is needed for a standard study; the contrast comes entirely from the brain's own blood. The patient simply follows the task instructions while lying still.

Functional MRI is most often used to plan treatment near sensitive parts of the brain. Before surgery, radiotherapy or other cranial procedures, it shows the relationship between a lesion, such as a tumour or an epileptic focus, and the areas that control speech, movement and sensation. This helps the medical team decide on the safest approach and protect vital functions. It is therefore especially valuable for patients with brain tumours, epilepsy or vascular conditions, and it is also used in research into how the brain works.

The great benefit of fMRI is that it provides a personalised map of an individual's brain function without any radiation or, usually, any injection. By showing exactly where critical areas lie, it helps surgeons and other specialists plan treatment that spares essential functions and reduces risk. During the scan the patient lies comfortably and is guided through the tasks by the team. The scanner makes loud tapping and knocking noises, for which ear protection is provided, and it is important to stay still and concentrate on the tasks. There is no recovery time, and the images are analysed by specialists who prepare a detailed functional map for the treating doctor.