Magnetic Resonance Imaging (MRI) is a noninvasive imaging technique. It is used to view organs, soft-tissue, bone, and other internal body structures. In a chest MRI, the person's body is exposed to radio waves while in a magnetic field. Cross-sectional pictures of the chest are produced by energy emitted from hydrogen atoms in the body's cells. An individual is not exposed to X-rays during this test.
A chest MRI can be used for a variety of purposes. This technique can be used to diagnose: lung cancerheart and vascular diseasedisorders affecting the airways and chest walldiseases of the heart valves, chambers and muscletears in the aorta, the body's largest artery
Before the test, the healthcare professional will ask if the person: has any drug allergies, or history of allergic reaction to medications is allergic to shellfish, or foods with added iodine such as table salthas experienced claustrophobia, or anxiety in enclosed spaces. If this is a problem, mild sedating medication may be given.
A woman will also be asked if she might be pregnant. The test is generally not done during the first three months of pregnancy. As the test begins, the person lies on a flat platform. The platform then slides into a doughnut-shaped magnet where the scanning takes place. To prevent image distortion on the final images, the person must lie very still for the duration of the test.
Commonly, a special substance called a contrast agent is administered prior to or during the test. The contrast agent is used to enhance internal structures and improve image quality. Typically, this material is injected into a vein in the arm. The scanning process is painless. However, the part of the body being imaged may feel a bit warm. This sensation is harmless and normal.
Loud banging and knocking noises are heard by the person during many stages of the exam. Earplugs are provided for people who find the noises disturbing. After the test, the person is asked to wait until the images are viewed to see if more images are needed. If the pictures look satisfactory, the person is allowed to leave.
Before the test, the person is asked to remove all metal objects that might affect imaging. These items include jewelry, hearing aids, hairpins, eyeglasses and removable dental work. Also, the person should inform the MRI technologist about any previous surgery which required placement of metal, such as a hip pinning. Internal metal objects that cannot be removed may distort the final images. Since the magnetic field can damage watches and credit cards, these objects are not taken into the MRI scanner. Food and fluid restrictions are not required before an MRI.
A specially trained physician called a radiologist analyzes the MRI images. Frequently, the chest MRI will help to better evaluate diseases of the heart, lung and chest wall. Chest MRIs can reveal the size and location of tumors, blood vessel abnormalities, heart problems, hemorrhages and other tissue abnormalities. This technique is useful in studying disorders of the ribs and sternum. The person's healthcare professional and the radiologist will use this information to help guide the treatment plan for the individual's condition.
Pagana, Kathleen D. and Timothy J. Pagana, Mosby's Manual of Diagnstic and Laboratory Tests, St. Louis, 1998.
"MR Imaging (MRI) - Body," Radiological Society of North America (RSNA), 2000.
Fauci, Anthony S., et. al., Harrison's Principles of Internal Medicine, 14th Edition, McGraw-Hill, New York, 1998.