Magnetic resonance imaging (or MRI) is a type of noninvasive imaging test that uses magnets and radio waves to create pictures of the inside of the body. Unlike a CT scan, an MRI uses no radiation and is considered a safer alternative, especially for pregnant women.
In a chest MRI, magnets and radio waves create black and white images of the chest, which allow doctors to check your tissues and organs for abnormalities without making an incision. MRIs also create images that “see” beyond your bones—and include soft tissue.
Your doctor may order an MRI scan if he or she suspects that something is wrong in your chest area and feels that the cause of the problem cannot be determined through a physical examination.
Your doctor may want you to undergo a chest MRI due to see if you have:
- blocked blood vessels
- disease affecting the organs
- heart problems
- needing to examine the lymph system
Your doctor will tell you the exact reason he or she ordered the MRI. Your doctor should keep you abreast of what he or she thinks could be wrong during and after the procedure. If you aren’t clear on what’s going on, make sure to ask plenty of questions.
Since an MRI does not use radiation, there are few, if any, side effects. To date, there have been no documented side effects from the radio waves and magnets.
According to the National Heart, Lung, and Blood Association, there are few risks from an MRI scan (NHLBA). If you have a pacemaker or metal implant from previous surgeries or injuries, be sure to tell your doctor beforehand and find out whether you can have an MRI. It is possible for these implants to complicate a scan or even to cause a malfunction.
In rare cases, the dye used for the test will cause an allergic reaction or worsen kidney function for those with kidney disease. However, this is an unlikely side effect.
If you are claustrophobic or have difficulty being in enclosed spaces, you may feel uncomfortable while in the MRI machine. Try to remember that there is nothing to fear. Your doctor may prescribe an anti-anxiety medication to help with your discomfort. In some cases, you might be sedated for the process.
Before the test, tell your doctor if you have a pacemaker. Depending on your type of pacemaker, your doctor may suggest another route for inspection, such as a CT scan. However, some pacemaker models can be reprogrammed before an MRI so they are not disrupted by the examination.
Also, the MRI uses magnets, which can attract metals. Tell your doctor if you have any type of metal implanted from previous surgeries, such as:
- artificial heart valves
You may need to fast for four to six hours before the exam—check with your doctor to be sure.
Your doctor may require the use of a special dye to highlight an area of concern. This dye, gadolinium, is administered through an IV. It is different from the dye used during a CT scan. While allergic reactions to the dye are rare, alert your doctor of any concerns before the dye is injected.
An MRI machine looks futuristic—it has a bench that slowly glides you into giant metal cylinder.
The technician will have you lie on your back on the bench. You may receive a pillow or blanket if you have trouble lying still on the bench. The technician will control the movement of the bench using a remote control from another room. He or she will communicate with you through a microphone and speakers.
The machine will make some thumping and whirring noises as the images are being taken. Many hospitals offer earplugs, while others have televisions or headphones to help you pass the time—the test can last up to 90 minutes.
As the pictures are being taken, the technician will ask you to hold your breath for a few seconds. You won’t feel anything during the test as the magnets and radio frequencies—similar to the waves of FM radio—cannot be felt.
You do not need to do anything after an MRI except put your clothes back on.
If the images are projected onto film, it can take some hours for the film to develop. It will also take some time for your doctor to review the images and interpret them. More modern machines display images on a computer, which allows your doctor to view them more quickly.
Preliminary results from a chest MRI may come within a few days, but comprehensive results can take up to a week or more. Your doctor will most likely call you in for an appointment to discuss your results, and plan a treatment for problems identified. If your results were normal, he or she may order more tests to help diagnosis the cause of your symptoms.