About an MR angiogram of the aorta
The aorta is the largest artery in the body. It carries blood from the heart, arches over in the chest and runs down through the abdomen, where it divides into the arteries that supply the legs. An MR angiogram (MRA) of the aorta uses a strong magnetic field, radio waves and a computer to make detailed pictures of it, without X-rays.
The scan is most often used to measure and monitor an aortic aneurysm, which is a swelling or bulge in the wall of the aorta. Most aneurysms cause no symptoms and are found by chance or through screening; in England, men are offered an ultrasound screening scan for abdominal aortic aneurysm when they turn 65. Because MRA does not use radiation, it can be a good choice when an aneurysm needs to be checked regularly. It is also used to look at a tear in the wall of the aorta (dissection), narrowing (such as coarctation), and the aorta before and after surgery or stent repair.
Referral needed: this scan requires a referral from a specialist, such as a neurologist, neurosurgeon, vascular surgeon or other hospital consultant. You can upload the referral when you book.
What happens during the scan
You lie on your back on the scanner bed with a coil placed over your chest or tummy. The scanner is loud, so you will wear ear plugs or headphones, and the radiographer can see, hear and talk to you throughout. You will need to keep your body very still, as even small movements can blur the pictures of the blood vessels.
Most MR angiograms use an injection of contrast dye (gadolinium) through a small cannula in a vein, usually in your arm or hand, so the blood vessels show up clearly. Gadolinium is less likely to cause an allergic reaction than the iodine-based dye used for CT. Some vessels can also be imaged without contrast. If you have contrast, you may be asked to wait for up to 30 minutes afterwards. Where contrast is needed, it is charged separately.
Because breathing moves the aorta, you will be asked to hold your breath for short periods while some pictures are taken.
What the scan can show
An MR angiogram of the aorta can help to look at:
- aneurysms of the aorta in the chest (thoracic) or tummy (abdominal), including their size and shape
- changes in the size of a known aneurysm over time
- aortic dissection, where the inner layer of the aortic wall has torn
- narrowing of the aorta, including coarctation, and narrowing where the main branches leave the aorta
- the aorta before surgery, or after an aneurysm repair or stent
- conditions present from birth that affect the aorta, and conditions such as Marfan syndrome that increase the risk of aneurysm
MRA does not show calcium in the artery wall as clearly as a CT angiogram. Your specialist will advise which test suits you best.
Emergency symptoms: sudden, severe pain in the tummy, back or chest, feeling faint, or pale or grey skin can be signs of a burst aneurysm or dissection. Call 999 straight away. This is not a reason to wait for a scan.
Preparing for your scan
You may be asked not to eat for a few hours before a scan of the abdominal aorta. The scanning centre will confirm this when you book. If you have had a previous ultrasound, CT or MRI of your aorta, upload the report when you book so any change in size can be measured.
You can usually eat, drink and take your normal medicines unless the scanning centre tells you otherwise. Wear loose, comfortable clothing without metal zips or buttons, and leave jewellery at home. You will be asked to remove metal items such as hair clips, hearing aids, coins and keys, and you may be asked to change into a gown.
Before the scan you will complete a safety questionnaire. Tell the team if you have a pacemaker, any metal implant, surgical clips or other device, if you have kidney problems or allergies, or if you are, or might be, pregnant or breastfeeding. If you feel anxious in enclosed spaces, let us know when you book. Some centres can offer a relaxant, and if you take one you will need someone to take you home and must not drive for 24 hours.
Frequently asked questions
Do I need a referral for an MR angiogram of the aorta?
Yes. This scan requires a referral from a specialist. Please upload your referral when you book so the scanning centre can check that the right scan is arranged.
Why would I have an MRA rather than an ultrasound?
Ultrasound is the main test for checking the abdominal aorta and is used for screening. MRA can show the whole aorta, including the part in the chest, and the arteries branching off it, which helps when planning treatment or monitoring a more complex aneurysm.
Does an MR angiogram use radiation?
No. MRA uses a magnetic field and radio waves, which makes it suitable when an aneurysm needs to be checked regularly over many years.
Will I need a contrast injection?
Usually, yes. Contrast dye helps the aorta and its branches show clearly. It is given through a small cannula in your arm and is charged separately where it is needed.
Sources
- RadiologyInfo.org – Magnetic Resonance Angiography (MRA)
- NHS – Abdominal aortic aneurysm
- NHS – MRI scan
The information on this page has been gathered from various sources and is provided for general information only. It is not medical advice. TOP MRI is not liable for the accuracy or completeness of this information. Please speak to your doctor or the scanning centre about your own situation.