CT Scan – Brain (Head)

About a CT scan of the brain

A CT (computed tomography) scan of the head uses X-rays and a computer to make cross-section pictures of the brain, the fluid spaces around it and the bones of the skull. The scan takes only a few seconds, which is why CT is the first test in hospital emergency departments for head injuries and suspected strokes: it quickly shows bleeding in or around the brain and skull fractures.

Those emergencies need hospital care, not a booked private scan. Outside emergencies, a head CT may be used to look at:

• the skull and bones of the head, including bony lumps
• build-up of fluid in the brain (hydrocephalus), including checking a shunt
• the result of an earlier bleed, operation or treatment
• headaches or other symptoms when MRI is not possible, for example if you have a pacemaker or other device that is not safe for MRI, or find MRI too difficult
• calcium deposits and some growths in the brain

For most non-urgent brain symptoms, such as long-term headaches, dizziness, memory problems, seizures or suspected multiple sclerosis, a brain MRI is usually the better test, because it shows the brain tissue in much more detail and does not use radiation. Most headaches are not caused by anything serious and do not need a scan at all. You can read more in our article on the difference between CT and MRI.

What happens during the scan

You lie on your back on the scanner bed with your head resting in a cradle, and pads may be used to help you keep still. Only your head goes into the scanner, which is a short, open ring. The radiographer controls the scanner from the next room, but can see, hear and talk to you throughout. The scan itself takes less than a minute. Contrast dye is not usually needed, but may be used to look at a growth or blood vessels; where contrast is needed, it is charged separately.

Is CT safe?

CT uses X-rays, which are a type of ionising radiation. A CT of the head gives a typical dose of about 2 mSv, similar to the natural background radiation you would receive from the environment over about 1 year. The risk from a single scan is very small, and every CT scan is checked by a radiologist or radiographer to make sure the benefit of the scan outweighs the risk, as required by the Ionising Radiation (Medical Exposure) Regulations. If you have had other CT scans recently, tell us when you book.