MRI is a scan that lets doctors see inside the body without having to perform surgery. The test is painless, and uses no radiation. Cardiac MRI is a test that gives doctors a detailed picture of the heart, including the chambers and valves, without patients having to undergo cardiac catheterization.

How does it work?

The MRI machine looks like a long, narrow tube. When you are placed inside of the tube, you are surrounded by a magnetic field. The human body is made up of different elements, most of which are also magnetic. The magnetic field surrounding your body reacts with the magnetic elements within your body to transmit a faint radio signal. For example, your body contains a large amount of hydrogen atoms, and those atoms are very magnetic. The MRI machine’s magnetic field excites the hydrogen atoms in your body, which in turn creates a small radio signal. A computer reads the radio signal and turns it into an image that can be seen on a computer monitor.

What should I expect?

No special preparation is needed before you have an MRI.

The MRI machine will surround you during the test, and some people may feel closed in or claustrophobic. You will have to lie still, and you may be asked to hold your breath briefly while the technician takes pictures of your heart.

An MRI is a completely painless test, and because the MRI machine uses magnetism, you are not exposed to any radiation like you would be with an x-ray machine. MRI cannot be done if you have a pacemaker.

Magnetic Resonance Angiography (MRA)

When doctors use an MRI machine to study the blood vessels leading to the brain, heart, kidneys, and legs, it is called magnetic resonance angiography (MRA). MRA uses the same technology as MRI, but technicians use special settings on the machine to detect and diagnose blood vessel diseases. MRA can usually give doctors very clear images of the blood vessels without exposing the patient to radiation. In some cases, a harmless dye may be used to make the images even clearer. The MRA dye highlights the blood vessels, making them stand out from the tissues around them.

If you are having an MRA procedure that does not require a contrast dye, the procedure will be just like an MRI procedure. If a contrast dye is needed, it will be injected (usually in your arm) over 1 to 2 minutes, and then more scans will be done. The dye used for the test is harmless.