An MRA scan, or magnetic resonance angiography, is a type of MRI that focuses specifically on your blood vessels. It uses radio waves, a magnetic field, and a computer to create detailed images of arteries and veins throughout your body, helping doctors spot problems like blockages, bulging vessels, or blood clots without surgery.
How MRA Differs From a Standard MRI
A standard MRI produces images of organs, bones, muscles, and other soft tissues. An MRA narrows that focus to blood vessels. It maps the flow of blood through your arteries and veins, generating a detailed picture of your vascular system that can reveal narrowing, clots, or structural abnormalities. The machine itself is the same, and the experience of lying inside the scanner feels identical. The difference is in how the scan is programmed and, in some cases, whether a contrast agent is injected to make blood vessels stand out more clearly.
What MRA Scans Detect
Doctors order MRA scans to evaluate a wide range of vascular problems. Common conditions include aneurysms (weak spots in a vessel wall that balloon outward), narrowing of the arteries from plaque buildup, blood clots in deep veins, and abnormal connections between arteries and veins. It can also detect tears in the wall of the aorta, congenital heart defects, and pulmonary embolism (a clot that travels to the lungs).
Brain MRAs are particularly common. They can identify brain aneurysms, evidence of a prior or ongoing stroke, and vascular malformations that might cause bleeding. If you’re experiencing unexplained headaches, dizziness, or neurological symptoms, a brain MRA is one of the first imaging tools your doctor may reach for.
With and Without Contrast
MRA scans come in two main varieties. The first, called time-of-flight MRA, works without any contrast injection. It detects the natural movement of blood through your vessels and uses that flow to generate images. This version is commonly used for brain and neck arteries.
The second type, contrast-enhanced MRA, involves an intravenous injection of a gadolinium-based dye. As the dye passes through your arteries, the scanner captures high-resolution images with less interference from surrounding tissue. Contrast-enhanced MRA typically covers a larger area of the body in a single scan and produces sharper images of tight narrowings in blood vessels. It’s often the preferred choice for imaging the chest, abdomen, and legs.
Your doctor will decide which type you need based on the body region being scanned and what they’re looking for.
How Long the Scan Takes
Most MRA scans take 45 to 60 minutes. Brain and spine studies average around 45 minutes. If contrast dye is used, expect the scan to run about 15 minutes longer. Cardiac MRA, which has to account for the constant motion of your heart and your breathing, can take 90 minutes to two hours. You’ll lie still on a narrow table that slides into a tube-shaped scanner. The machine produces loud knocking and buzzing sounds, and you’ll typically be given earplugs or headphones.
How to Prepare
Preparation for an MRA is generally straightforward. For most scans, you won’t need to fast or change your medications. If your scan involves contrast, the imaging center may ask you to avoid eating solid food for four hours beforehand. You’ll change into a hospital gown and remove all jewelry, watches, hair clips, and anything else metallic.
The most important preparation step is reviewing your medical history with the imaging team, especially regarding any implants or metal in your body. Before the scan, you’ll fill out a screening questionnaire about prior surgeries, injuries, and devices.
Who Cannot Have an MRA
Because MRA uses a powerful magnet, certain implants and metal objects make the scan unsafe. Pacemakers, implantable defibrillators, and cardiac resynchronization devices pose significant risks during scanning. Other absolute contraindications include cochlear implants, implantable drug infusion pumps, neurostimulation devices, and cerebral aneurysm clips. Metallic foreign bodies, particularly fragments near the eyes from welding or facial trauma, can shift inside the magnetic field and cause injury. Patients with that kind of history typically need an orbital X-ray to confirm it’s safe before proceeding.
Bullets, shrapnel, certain dental implants, body piercings, and catheters with metallic components are also concerns. The general rule: if an implant or device hasn’t been specifically verified as safe for MRI, it’s treated as unsafe.
Gadolinium Contrast and Kidney Safety
The gadolinium-based contrast used in MRA is generally safe, but it carries a specific risk for people with severely reduced kidney function. The body relies on the kidneys to flush gadolinium out. When kidney function is poor, the contrast agent lingers, and in rare cases this can trigger a condition called nephrogenic systemic fibrosis, which causes painful swelling and hardening of the skin that can progress to limited mobility. There is no known cure.
For this reason, doctors typically check your kidney function with a blood test before ordering a contrast-enhanced MRA. People with end-stage kidney disease, those on dialysis, or anyone with an estimated kidney filtration rate below 30 are generally steered toward non-contrast alternatives. If contrast is truly necessary in a high-risk patient, newer formulations of gadolinium with more stable chemical structures carry a much lower risk. Guidelines also recommend waiting at least seven days between two gadolinium injections.
For people with normal kidney function, the contrast is processed and eliminated quickly, and the risk of complications is very low.
MRA vs. CT Angiography
CT angiography (CTA) is the other major option for imaging blood vessels. It uses X-rays and an iodine-based contrast dye instead of magnets. Both tests are effective, but they have different strengths.
MRA avoids radiation exposure entirely, which matters if you need repeated scans over time. It also uses gadolinium rather than iodine contrast, making it a better option for people with iodine allergies. CTA scans are faster, often completing in just a few minutes, and tend to produce sharper images of very small vessels. For detecting aneurysms, both methods perform well for medium and large aneurysms (sensitivity around 86 to 92% for those over 5 mm). Both struggle with very small aneurysms under 3 to 5 mm, where detection rates drop significantly.
Your doctor will choose between the two based on what part of the body needs imaging, how quickly results are needed (CTA is typical in emergency settings), and your individual risk factors like kidney function, allergies, or radiation concerns.
Getting Your Results
After the scan, a radiologist reviews your images and sends a report to the doctor who ordered the test. Turnaround time varies by facility. Routine results typically reach your doctor within one to three business days, though urgent or emergency scans are often read within hours. Your referring doctor will then contact you to discuss findings and any next steps. Many imaging centers now also upload results to online patient portals, so you may be able to see the report before your follow-up appointment.