An MRI scan uses magnets and radio waves to capture images of your body’s internal structures. It doesn’t involve a surgical incision. The scan allows your doctor to see your bones as well as soft tissues of the body, including muscles, ligaments, tendons, and even nerves and blood vessels.
While an MRI can be performed on any part of your body, a shoulder MRI scan specifically helps your doctor see the bones, blood vessels, and tissues in your shoulder region.
A shoulder MRI helps your doctor diagnose potential problems found in other imaging tests, such as X-rays. It also helps your doctor diagnose unexplained pain in the area or better understand the condition causing your shoulder symptoms.
An MRI scan works by generating a magnetic field which temporarily aligns the water molecules in your body. Radio waves use these aligned particles to produce faint signals, which are recorded as images by the machine.
Unlike X-rays and CT scans, an MRI uses no radiation and is considered a safer alternative, especially for pregnant women and children.
The shoulder is a large and complicated joint that we use on a daily basis. It’s made up of three major bones. This makes it the most mobile joint in the body. As a result, numerous problems can affect our shoulders.
Pain or an injury are the main reasons your doctor might order an MRI scan. The injury could be the result of an impact, or simply the effect of long-term wear and tear on the joint. Specific problems that could require a shoulder MRI scan include:
- dislocation of the shoulder joint
- degenerative joint diseases, such as arthritis
- rotator cuff tears
- bone fractures
- sports-related injuries
- unexplained pain and swelling
- decreased range of motion
- Infections or tumors
In some cases, an MRI scan can help your doctor track the effect of surgeries, medications, or physical therapy on your shoulder.
MRI scans carry few risks since they don’t use radiation. To date, there have been no documented side effects from the radio waves and magnets used in the scan. Still, people with certain conditions do face some risks.
If you have implants containing metal, it can cause problems with an MRI. The magnets used in an MRI can interfere with pacemakers or cause implanted screws or pins to shift in the body. Be sure to tell your doctor if you have any of the following implants:
- artificial joints
- artificial heart valves
- metal clips from aneurysm surgery
- bullet or other metal fragments
- a pacemaker
If you have a pacemaker, your doctor may suggest another method for inspecting your shoulder area, such as a CT scan. This depends on your type of pacemaker. Some pacemaker models can be reprogrammed before an MRI so that they are not disrupted during the examination.
Some people can have an allergic reaction to the contrast dye. Contrast dye helps provide a clearer image of the blood vessels. The most common type of contrast dye is gadolinium. According to the Radiological Society of North America (RSNA), these allergic reactions are often mild and easily controlled with medication. Be sure to tell your doctor about any allergies or if you’ve had an allergic reaction in the past.
Women shouldn’t breast-feed 24 to 48 hours after they have been given contrast dye. They need to wait for the dye to leave their bodies.
Tell your doctor if you have any metal in your body from previous procedures or injuries. You’ll need to remove any metal from your body, including jewelry and body piercings before the test. You’ll change into a hospital gown so that metal on your clothing doesn’t affect the test.
If you’re claustrophobic or have a hard time in enclosed spaces, you may feel uncomfortable while in the MRI machine. Your doctor may prescribe anti-anxiety medication to help with your discomfort. In some cases, you may also be sedated during the test.
If your test requires the use of contrast dye, a nurse or doctor will inject it into your bloodstream through an intravenous line. You may need to wait for the dye to circulate through your body before beginning the test.
An MRI machine is a giant white tube with a sliding bench attached to it. You’ll lie on your back on the table and slide into the machine. A technician will place small coils around your shoulder to improve the quality of the scan images.
The technician will control the movement of the bench using a remote control from another room. They can communicate with you via a microphone.
The machine will make loud whirring and thumping noises as the images are being recorded. Many hospitals offer earplugs. Others have televisions or headphones to help you pass the time.
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.
A typical shoulder MRI takes 45 minutes to an hour to complete.
After your shoulder MRI, you’re free to leave the hospital unless your doctor tells you otherwise. If you were given a sedative, you need to wait to drive until the medication has fully worn off. Or, you can arrange for a ride home after the test.
If your MRI images were projected onto film, it might take a few hours for the film to develop. It will also take some time for your doctor to review the images and interpret the results. More modern machines display images on a computer, so your doctor can view them quickly.
The initial results from an MRI scan may arrive within a few days, but comprehensive results can take up to a week or more.
When the results are available, your doctor will call you in to review and explain them. More tests may be necessary to make a diagnosis.