Cardiac magnetic resonance (CMR) imaging is an MRI for your heart. It uses powerful magnets to create pictures of the heart and coronary arteries. During this test, you're placed in a chamber surrounded by a magnetic field. In response to the magnetic force, the atoms that make up your body's tissues produce weak signals. With the help of a computer, these signals are magnified and recorded. They can then be used to create cross-section views ("slices") of your heart as well as three-dimensional images. These can be still or motion pictures.
CMR can reveal the structure and size of the heart chambers, wall, and valves. It can also be used to show blood flow to and through the heart, and measure your ejection fraction. These images can help healthcare providers determine the extent of heart muscle damage (as from a heart attack), assess blood flow problems, and detect and evaluate leaking in the heart's chambers and valves.