Magnetic Resonance Imaging (MRI Scanning)

MRI scanning (magnetic resonance imaging) has been in use since the early 1980’s. The MRI scan uses magnetic and radio waves and this means there is no exposure to X-rays or any other potentially damaging forms of radiation. There are no known dangers or side effects connected to an MRI scan and the test is not painful. Since radiation is not used, the procedure can be repeated without problems. For pregnant women, there could be a small risk to the foetus in the first 12 weeks of pregnancy and therefore scans are not performed on pregnant women during this time.

The patient lies inside a large, cylinder-shaped magnet. Radio waves are then sent through the body. The scanner picks up these signals and a computer turns them into a picture. The machine also makes a banging noise while it is working, which might be a little unpleasant but is nothing to worry about. An MRI scanner can take pictures of almost all the tissues in the body including parts of the body thatare surrounded by bone tissue During the test a liquid dye is injected to help make things easily visible. A small minority of patients are allergic to the liquid dye, and you will be asked if you have ever had any such allergic reaction.

In the investigation of PH, the MRI scan is able to show both the heart and the large blood vessels in the surrounding tissue. This makes it possible to detect heart defects that have been there since birth, (such as holes in the heart). With an MRI scan it is possible to take pictures from more angles and in more detail than a CT scan. The difference between normal and abnormal tissue is also often clearer on the MRI scan than on the CT scan.

The scan can be done as an outpatient procedure, which means that the patient can go home after the test. During the scan it is important that the patient lies completely still. As with the CT scan, because patients have to lie inside a large cylinder while the scans are being performed some people can feel claustrophobic during the test. Patients who are afraid this might happen should talk to the doctor beforehand, who may give them some medication to help them relax. Small children need sedation and so may have to stay in hospital overnight, until they are really awake!

Since the patient is exposed to a powerful magnetic field during the MRI scan, it is important that they do not wear jewellery or any other metal objects. It is also important for the patient to inform the staff doing the test if they use electrical appliances, such as a hearing aid or pacemaker or have any metal in their body such as surgical clips. The pumps that are used to deliver some of the drugs used in the treatment of PH, such as Flolan and Treprostinil, will cause a problem to an MR scanner. Again it is important to ensure that the staff are fully aware of these, don’t assume that they will know you are wearing a pump!