Imaging techniques

The two main imaging techniques available are magnetic resonance imaging (also referred to as MRI) and a computerised tomography (or CT) scan.

These imaging techniques can be carried out without you having to stay overnight in the hospital, although if you live a long way from the hospital you may need to arrange to stay overnight somewhere.

Both MRI and CT require the injection of a ‘dye’ called contrast media to help highlight the pituitary tumour from the normal pituitary tissue and other surrounding structures.

Most people tolerate the injection of this contrast medium, but there is a very small risk of an allergic reaction. You will be asked about your previous history of allergic reactions to ensure that this causes no unwanted effects.

Almost all people with acromegaly confirmed by blood tests will have a pituitary tumour that is detectable on MRI. In most (more than two thirds) people the tumour will be around 1 cm across or larger (called a macroadenoma), with around one third of people having a tumour that is less than 1 cm (called a microadenoma).

MRI uses a magnetic field and radio waves to make detailed pictures of the organs and structures inside your body.

MRI is the best imaging technique to detect the tumour and to pinpoint its size and location in the pituitary gland.

Information from MRI can help you and your healthcare team to decide if surgery will be the best acromegaly treatment option for you.

What happens during MRI?

Before your scan, you may be injected with a contrast agent, or ‘dye’.  The contrast agent highlights the parts of the body being scanned and can give more information to the radiologist.

You will be asked to lie very still on a bed that is moved inside the MRI scanner, which is like a cylindrical tube, for about 30 to 60 minutes.  You will not feel anything, however the MRI scanner is very noisy. You can ask for headphone or ear plugs.

Some people find it difficult being in small spaces or are anxious about being inside the scanner.  Tell your doctor if you experience claustrophobia (fear of small spaces). They may be able to recommend something to help you relax or use a different imaging technique.

There are no known side effects of MRI.

If you are required to have an injection of a contrast agent before the MRI, there is a very small risk of an allergic reaction. The chance of an allergic reaction to the contrast agent is very small, but please ask the MRI radiographer about the injection if you would like more information.

Can MRI be performed on everybody?

Most people can have a MRI scan, however there are certain people who may not be able to have this type of scan.

People with implants such as a pacemaker and other devices cannot have an MRI scan.  If you have a pacemaker or other implants, it is important to tell the radiology practice before having the scan.  An alternative test might need to be arranged.

Metal interacts with the magnet and can cause serious harm to the patient.  Objects in your body that can cause particular harm or be damaged include pacemakers, aneurysm clips, heart valve replacements, neurostimulators, cochlear implants, metal fragments in the eye, metal foreign bodies, magnetic dental implants and drug infusion pumps. Some of these implants, might be safe to go into the MRI scanner, Take any documents about your implants to the appointment. These can help to correctly identify the type of implant to assess if it is safe for you to have the MRI.

If you are pregnant, please discuss this with your doctor and tell the radiology practice before having the scan.  This will not necessarily stop you from having the scan. There are no reported effects of an MRI on the unborn child, but caution is always used in pregnancy. Intravenous contrast agent is not given in a pregnant female.

When you arrange to have a MRI scan, you may experience a wait time of several weeks (4-6 weeks) before the scan can be done. In most instances this is not concerning, as acromegaly is not considered an urgent reason for immediate scanning. But do let your endocrinologist know if you are concerned about an excessive wait time.

A CT scan is another imaging technique that can be used.

Your doctor may order a CT scan if you cannot have an MRI scan (for example, if you have a pacemaker or other implant that has metal).

CT scans use a combination of X-rays (rather than radio waves) and computer technology to create detailed pictures of the body’s internal organs.

This provides useful information about the position and size of the tumour in the pituitary gland.

What happens during the CT scan?

Similar to MRI, you will be asked to lie very still on a bed that is moved inside the CT scanner for around 10 to 20 minutes. A ring inside the scanner moves around you in a circle as it takes X-ray images.

You will not feel anything, however the CT scanner makes clicks and buzzes while taking the images.

Can CT be performed on everybody?

Some people find it difficult being in small spaces or are anxious about being inside the scanner.  Tell your doctor if you experience claustrophobia (fear of small spaces). The doctor may give you a mild sedative to help you relax during the procedure.

If you are pregnant, or think you might be pregnant, talk to your doctor. CT scans are best avoided in pregnancy, as there is a risk that the radiation could harm the unborn baby.

A medically qualified radiologist will assess your scans and send the results to your referring doctor (usually the endocrinologist).

The endocrinologist will then discuss the results with you, as well as possible treatment options. The endocrinologist will also consider involving a pituitary neurosurgeon at this point in time.

This process can take anything from a few days to a few weeks.  Book a follow up appointment with your doctor before, or immediately after your scan, to make sure you get your results as soon as possible.