Magnetic resonance imaging, or MRI, is a diagnostic scanning device that allows doctors see inside the body without performing surgery. The test is painless. Cardiac MRI creates a detailed picture of the heart, including its chambers and valves.
How It Works
The MRI machine looks like a long, narrow tube or large circle. When a patient is inside or under the MRI, he or she is surrounded by a magnetic field. The human body is made up of different magnetic elements or atoms. The machine’s magnetic field surrounding the body excites the magnetic atoms within the body, causing them to transmit a faint radio signal. A computer reads the radio signal and turns it into an image that can be seen on the monitor and printed on paper.
What To Expect
No special preparation is needed before an MRI. The MRI machine surrounds the patient during the test, scanning back then forth over the targeted area. Depending on the age of the machine, it may feel closed in or claustrophobic. The patient needs to lie very still and may be asked to hold his or her breath briefly while the technician takes pictures of the heart. An MRI is a completely painless test, but because the MRI machine uses magnetism, MRI cannot be performed on patients with a pacemaker.
Magnetic Resonance Angiography (MRA)
When doctors use MRI 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. An MRA procedure that does not require a contrast dye will be just like an MRI. If contrast dye is needed, it will be injected (usually in the arm) over 1 to 2 minutes, and then more scans will be done. The dye used for the test is harmless.
Texas Heart Institute www.texasheartinstitute.com/HIC/Topics/Diag/dimri.cfm