This scan uses a magnetic field to build up cross-sectional pictures of your brain. Before the test, some people are given an injection of dye into a vein in the arm to improve the pictures.

During the test you will be asked to lie very still on a couch inside a long chamber for up to an hour. This can be unpleasant if you don’t like enclosed spaces; if so, it may be helpful to mention this to the radiographer. The MRI scanning process is also very noisy, but you will be given earplugs or headphones to wear.

The cylinder is a very powerful magnet, so before entering the room you should remove any metal belongings. People who have metal heart monitors, pacemakers or some types of surgical clips cannot have an MRI because of the magnetic fields.

This is a series of x-rays, which builds up a three-dimensional picture of the inside of your head. During the test you will be asked to lie with your head inside an opening in the scanner. The scan is painless but takes longer than a normal x-ray (from 5–10 minutes). It may be used to identify the exact area and size of the tumour.

Most people who have a CT scan are given an injection of a liquid into a vein, to allow particular areas of the brain to be seen more clearly. The injection may make you feel hot all over for a few minutes. Before having the injection, it is important to tell your doctor and the person doing the scan if you are allergic to iodine or have asthma or diabetes.

You will probably be able to go home as soon as the scan is over.

Very rarely, brain tumours may show up on an x-ray picture. The test is simple and painless, but you will have to lie on a couch in the hospital’s x-ray department and keep your head still for a few minutes.

A chest x-ray will usually be done to make sure that your lungs are healthy and to look for a possible primary tumour in the lung.

A PET scan uses low-dose radioactive glucose (a type of sugar) to measure the activity of cells in different parts of the body. A very small amount of the mildly radioactive substance is injected into a vein, usually in your arm. Tumours normally absorb more of the glucose and the radioactivity shows up on the scan.

A PET scan may help to tell whether a tumour is growing and whether it is cancerous (malignant) or benign. After the injection is given you may be asked to lie in a dark room with your eyes closed. You will then be taken to the scanning room and asked to lie on a couch with the scanning ring around you. The dose of radiation you receive is no more than a normal x-ray.

PET scans aren’t available in all hospitals, and you may have to travel to a hospital some distance away from your home to have one.

This is a recording of the electrical activity within the brain. During the test, wires connected to small plastic discs are attached to your head using a special gel. The recorded nerve impulses are then printed out on paper. The test takes about an hour. It is safe and completely painless. Your hair does not need to be cut and the gel will wash out easily afterwards.

It is often necessary for the doctor to take a small part of the tumour (a biopsy) to find out exactly what type of tumour you have (see Surgery for more information).