Tests for primary brain tumours

You may have tests to diagnose or find out more about a primary brain tumour. Some people have these while they are in hospital. But you can usually have tests as an outpatient and go home shortly after.   

Tests may include: 

  • Brain CT scan – a series of x-rays create a three-dimensional image of the brain.
  • Brain MRI scan – magnetism produces a detailed picture of the brain.
  • PET scan – low-dose radioactive glucose helps show tumour cells. 
  • Biopsy – a small part of the tumour is removed to find out more.
  • Lumbar puncture – a needle is used to take a sample of cerebrospinal fluid (CSF).
  • Blood tests – to check for hormones or chemicals released by some types of tumours.
  • Chest x-ray – to check your lungs and general health.

It can be difficult waiting for test results. You may find it helpful to talk with someone close to you or your specialist nurse. You can also talk things over with one of our cancer support specialists on 0808 808 00 00.

Brain CT (computerised tomography) scan

A CT scan takes a series of x-rays, which build up a three-dimensional picture of the brain. The scan takes only a few minutes and is painless. It uses a small amount of radiation, which is very unlikely to harm you and will not harm anyone you come into contact with.

You may be given an injection of a dye, which allows particular areas to be seen more clearly. This may make you feel hot all over for a few minutes. It is important to let your doctor know if you are allergic to iodine or have asthma, because you could have a more serious reaction to the injection.


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Someone having a CT scan

Having a CT scan

A radiographer explains how a CT scan works, and Jyoti talks about her experience.

About our cancer information videos

Having a CT scan

A radiographer explains how a CT scan works, and Jyoti talks about her experience.

About our cancer information videos

Brain MRI (magnetic resonance imaging) scan

This test uses magnetism to build up a detailed picture of your brain. It can also be used to check your spine.

The scanner is a powerful magnet so you may be asked to complete and sign a checklist to make sure it’s safe for you. The checklist asks about any metal implants you may have, for example a pacemaker, surgical clips or bone pins. You should also tell your doctor if you ever worked with metal or in the metal industry as very tiny fragments of metal can sometimes lodge in the body. If you do have any metal in your body, you may not be able to have an MRI scan. In this situation, another type of scan can be used.

Before the scan, you are asked to remove any metal belongings, including jewellery. You are given an injection of dye into a vein in the arm, which doesn’t usually cause discomfort. This is called a contrast medium and can help the images from the scan to show up more clearly.

During the test, you lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It is painless but can be slightly uncomfortable, and some people feel a bit claustrophobic. It is also noisy, but you will be given earplugs or headphones. You can hear, and speak to, the person operating the scanner.

Sometimes specialised types of MRI scans are used to look at blood vessels (MR angiography) or chemical activity (MR spectroscopy) in the brain.

PET (positron emission tomography) scan

A PET scan uses low-dose radioactive glucose (a type of sugar) to measure the activity of cells in different parts of the body. Tumour cells may use the glucose differently than normal cells so they look different on the scan. Another type of PET scan called single photon emission computerised tomography (SPECT) looks at the blood flow through the brain.

A very small amount of a mildly radioactive substance is injected into a vein, usually in your arm. A scan is then taken a couple of hours later. Not all hospitals have PET scanners, so you may have to travel to another hospital if you need this test.


A biopsy is when your doctor removes a small part of the tumour to find out the exact type of tumour you have. A brain tumour biopsy is often done at the same time as surgery to remove the tumour.

We have more details about having a biopsy and surgery.

Lumbar puncture

Sometimes doctors will want to take a sample of your cerebrospinal fluid (CSF) to check for tumour cells. The doctor or nurse uses a local anaesthetic to numb your lower back. They put a needle in between two of the bones of your back and collect a small amount of CSF. This is called a lumbar puncture.

Some people have a headache for a few hours after this. You may have to lie flat for up to several hours afterwards, depending on how you feel.

Let the doctor or nurse know if you have a headache, as mild painkillers can help.

Blood tests and chest x-rays

A blood test cannot diagnose a brain tumour. But some types of tumour release certain hormones or chemicals into the blood. If the tumour is affecting your pituitary gland or pineal gland, you may have blood tests to check for this.

Some people may have a chest x-ray to check their lungs and their general health.

Waiting for test results

Waiting for test results can be a difficult time. It may take from a few days to a couple of weeks for the results of your tests to be ready. You may find it helpful to talk with your partner, family or a close friend. Your specialist nurse can also provide support. You can also talk things over with one of our cancer support specialists on 0808 808 00 00.

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Risk factors and causes

There are some risk factors that increase the chances of developing a primary brain tumour.