CT Angiogram and MR Angiogram

Sometimes the question is not about the brain or spine itself but about the blood vessels that supply them. CT angiograms and MR angiograms are scans that show those blood vessels clearly, without a catheter.

• CT angiogram (CTA): a CT scan done while iodine contrast dye is injected through an IV. The dye fills the blood vessels so they show up in detail. It takes only a few minutes.
• MR angiogram (MRA): an MRI that shows blood vessels. Some MRAs need gadolinium contrast through an IV, and some do not need any dye at all.

Both create 3D pictures of the arteries in the brain and neck, and sometimes the spine.

CTA and MRA can show:

• Brain aneurysms (bulges in an artery wall)
• Arteriovenous malformations (AVMs) and other abnormal blood vessel connections
• The cause of bleeding in the brain
• Narrowing or blockage of the arteries in the neck or brain, which can cause strokes
• The blood supply around a tumor before surgery
• The position of the arteries in the neck before some neck surgeries

If a CTA or MRA finds a problem that needs a closer look or treatment, the next step is often a cerebral angiogram.

• For a CTA: tell the center about any allergy to iodine contrast, kidney disease, or if you take metformin for diabetes. You may be asked not to eat for a few hours before.
• For an MRA: follow the steps for an MRI, including telling the center about any implants. If gadolinium will be used, see MRI with and without contrast.
• Tell them if you might be pregnant.
• Drink plenty of water the day before unless you have been told to limit fluids.

For a CTA, an IV is placed and the scan takes only a few minutes; the dye may cause a warm, flushed feeling or a metallic taste for a moment. An MRA feels like a regular MRI and takes about 30 to 60 minutes.

You can go back to normal activities right away. If you had contrast dye, drink extra water for the rest of the day. A radiologist reads the scan, and the doctor who ordered it will go over the results with you.

Both tests are safe for most people. A CTA uses some radiation and iodine dye, which can rarely cause an allergic reaction or affect kidney function in people with kidney disease. An MRA uses no radiation. The imaging center screens for these risks before your scan.

What is the difference between a CTA and an MRA?

Both show blood vessels. A CTA is a fast CT scan with iodine dye. An MRA is an MRI that may use gadolinium dye or no dye at all, and it uses no radiation.

Can a CTA or MRA find a brain aneurysm?

Yes. Both are commonly used to look for aneurysms. A cerebral angiogram may be used to look more closely or to plan treatment.

Do I need to fast before a CT angiogram?

Some centers ask you not to eat for a few hours before a contrast CT. Follow the instructions from your imaging center.

If Dr. Grunch has ordered a CT or MR angiogram for you and you have questions, call 470-293-9800 or contact us. You can also ask general questions any time through our “Ask Us Anything” chat. For questions about scheduling, cost or arrival time for the test itself, call the imaging center where it is booked.

Related: All imaging and diagnostic tests · Cerebral angiogram · Intracranial hemorrhage

This information is for educational purposes only and is not medical advice. It does not replace individualized care from a licensed physician. Please talk to your provider about your symptoms and follow the instructions from your imaging center.