A magnetic resonance imaging (MRI) scan uses magnets and radio waves to capture images of your body’s internal structures without making a surgical incision. The scan allows your doctor to see the soft tissues of the body, including muscles, ligaments, and tendons, in addition to your bones.
While an MRI can be performed on any part of your body, a shoulder MRI scan specifically helps your doctor see the bones, organs, blood vessels, and other tissues in your shoulder region. This helps your doctor inspect potential problems found in other imaging tests, such as X-rays; diagnose unexplained pain in the area; or better understand the condition causing your shoulder symptoms.
Unlike X-rays and computed tomography (CT) scans, an MRI uses no radiation and is considered a safer alternative, especially for pregnant women.
The shoulder is a large and complicated joint that we use on a daily basis. It is made up of three major bones, which meet at three major joints. This makes it the most mobile joint in the body. Because of this, numerous problems can affect our shoulders.
Injury is the main reason 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
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 do not use radiation. To date, there have been no documented side effects from the radio waves and magnets used in the scan.
However, there are risks for those who have implants containing metal. The magnets used in an MRI can cause problems 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
- a pacemaker
- metal clips from aneurysm surgery
- bullet or other metal fragments
One complication that can also arise is an allergic reaction to the contrast dye. The most common type of contrast dye is gadolinium. The Radiological Society of North America states that these allergic reactions are often mild and easily controlled with medication. (RSNA) Women are advised not to breastfeed their children 24 to 48 hours after they have been given contrast dye to give it time to leave their bodies.
If you are claustrophobic or have a hard time in enclosed spaces, you may feel uncomfortable while in the MRI machine. Your doctor may prescribe antianxiety medication to help with your discomfort. In some cases, you may also be sedated during the test.
Tell your doctor if you have any metal in your body from previous procedures or injuries. You will need to remove any metal from your body, including jewelry and body piercings, before the test. You will change into a hospital gown so that metal on your clothing does not affect the test.
Be sure to tell your doctor before the test if you have a pacemaker. Depending on the type of pacemaker, your doctor may suggest another method for inspecting your shoulder area, such as a CT scan. Some pacemaker models can be reprogrammed before an MRI so that they are not disrupted during the examination.
Some MRI examinations use contrast dye that is injected into the bloodstream through an IV line. This helps provide a clearer image of the blood vessels in that area. The dye can cause an allergic reaction in rare cases. Tell your doctor about any allergies you have or if you’ve had an allergic reaction in the past.
According to the Mayo Clinic, the magnetic field generated by the MRI 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. (Mayo)
If your test requires the use of contrast dye, a nurse or doctor will inject it into your bloodstream through an IV 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 will 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. (Cedars-Sinai)
The technician will control the movement of the bench using a remote control from another room. He or she will be able 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, while 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 will not feel anything during the test, as the magnets and radio frequencies—similar to those of FM radios—cannot be felt.
A typical shoulder MRI takes 45 minutes to an hour to complete.
After your shoulder MRI, you are free to leave the hospital unless your doctor tells you otherwise. If you were given a sedative, you will 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 them and fully explain the results. He or she may want to order more tests to make a diagnosis.