The most common investigations to undergo for a suspected brain tumour are a Computed Tomography (CT) scan and/or a Magnetic Resonance Imaging (MRI) scan. They may be performed for initial investigation or to help in the planning of your surgery (for neuronavigation), in which case you may have some small plastic dots (fiducials) stuck onto your head before the scan.

Computed Tomography (CT)

CT is an imaging test in which many x-rays are taken of the head from different angles. These images are combined by a computer to produce cross-sectional pictures of the brain. Except for the injection of a dye (needed in most but not all cases), this is a painless procedure that can be done as an outpatient. Modern CT scans take only a few minutes to perform and involve lying on a table that moves you into the scanner (which is open at both ends), and staying still for a few minutes.

As a CT uses X-rays (which may harm a foetus), it is important to know if female patients are pregnant so that the abdomen can be shielded or alternative scanning techniques used. Any known allergy to contrast (dye) should be reported.

Magnetic Resonance Imaging (MRI)

MRI is a body imaging system employing a magnet which surrounds the patient. A magnetic field causes small harmless movement of atoms in the head and a low energy radio wave is then passed through the same area. The minute change this imparts to the atoms in the magnetic field causes signals to be emitted which are picked up and analysed by modern computer technology. An image of the brain is produced in clear detail.

An MRI scan takes longer than a CT scan but again involves lying still on a table that moves you into the scanner. Unlike CT, the space is more enclosed and patients with severe claustrophobia may find it intolerable or require sedation before the scan. The machine makes a banging sound during scanning and you may be given headphones or ear plugs. You can talk to or summon the operator at any time. Again you may be given an injection of dye during the scan.

As the MRI does not involve X-rays there is not any known risk to a foetus but it is advisable for female patients to report any pregnancy to the staff anyway. As the scan relies on a strong magnetic field you will be asked to remove any magnetic objects from your person and you should report to the staff any metal implants (pacemakers, stimulators, internal ear implants, aneurysm clips, metallic heart valves, metallic splinters, etc.).