Dr Julie Olliff
Queen Elizabeth Hospital, Birmingham

Before MRI and CT scans, only X-rays were available for confirming pituitary tumours. However, due to the restrictions of X-rays they could only identify very large tumours.

MRI and CT scans are now used in several situations:

• Investigation and diagnosis (such as visual problems, hormone disturbance, headaches).
• To measure the size of the tumour (microadenoma less than 1 cm in diameter, macroadenoma greater than 1 cm in diameter) and to determine treatment, including possible surgery. The surgeon will use the information to determine his approach to surgery.
• Follow up of surgery.
• Follow up of medical treatment.

CT (Computed Tomography)

CT was invented by Sir Godfrey Hounsfield, who won a Nobel Prize for his work. They were an incredible improvement on X-rays but have several limitations:

• They can only scan one plane (usually axial which is not the best for pituitary tumours).
• They still use X-rays, (which is potentially harmful) but the dosage from a CT scan is taken into consideration when assessing the benefit from the CT scan. It amounts to several chest X-rays. X-rays are present in our environment with a plane flight across the Atlantic giving roughly the same dose as one chest X-ray and a person living in a granite house in Cornwall receiving a dose equivalent to a CT scan.
• They need an injection of contrast fluid that contains iodine and may cause allergies. This fluid shows the pituitary and blood vessels much whiter.

The advantages of CT over MRI scans are:

• The doughnut-shaped tube is smaller than a MRI and is more acceptable to many patients.
• They are cheaper than MRI (approximately £120 per CT, £200-£250 per MRI, plus the contrast fluid £50 for MRI).
• They are more readily available.

MRI (Magnetic Resonance Imaging)

MRI was pioneered in the UK. They use a powerful homogenous magnetic field and radio waves, which work on the water within all cells. The magnet is housed in a long tube to even out the magnetic field. Each scan takes between three and five minutes.

The advantages of MRI over CT scans are:

• They do not use X-rays.
• They can scan in any plane.
• They show the pituitary with superior resolution.
• The injection is less likely to cause an allergic reaction (it contains gadolinium).

The disadvantages are:

• The scanner can be claustrophobic. (If this is a problem consider asking your GP for some diazepam, but do not drive.)
• They can be very noisy, especially the newer more powerful scanners. (You can ask for headsets or earplugs.)
• The scan time is longer, so you need to stay still longer.
• They are not so readily available.
• They are expensive.
• Patients with pacemakers, some clips and coils may not be able to use them. It is very important that you let the MRI team know.
• Metal objects react to the strong metal field and can be very dangerous. For example, a key or safety pin left in a pocket can fly across the room. It is very important that no metal objects are taken into the MRI room.

Microadenomas (less than 1 cm at diagnosis) are commonly seen in women and may cause infertility. They may be difficult to identify on the scans, especially before a contrast injection has been used.

A series of wonderful images were shown, illustrating various types and sizes of tumours, empty sellas, the optic nerves and chiasma and the nearby blood vessels.