Magnetic Resonance Imaging (MRI) of the Shoulder

Test Overview

Magnetic resonance imaging (MRI) is a test done with a large machine that uses a magnetic field and pulses of radio wave energy to make pictures of the shoulder. Muscles, ligaments, cartilage, and other joint structures are best seen with an MRI. In many cases MRI gives information about structures in the body that cannot be seen as well with an X-ray, ultrasound, or CT scan.

For an MRI test, you are placed inside the magnet so that your shoulder is inside the strong magnetic field. MRI can find changes in the structure of organs or other tissues. It also can find tissue damage or disease, such as infection or a tumor. Pictures from an MRI scan are digital images that can be saved and stored on a computer for further study. The images also can be reviewed remotely, such as in a clinic or an operating room. Photographs or films of selected pictures can also be made. See MRI images of the rotator cuff .

In some cases, a contrast material may be used during the MRI scan to show certain structures more clearly in the pictures. The contrast material may be used to check blood flow, find some types of tumors, and show areas of inflammation or infection. The contrast material may be put in a vein (IV) in your arm or directly into your shoulder joint.

See pictures of a standard MRI machine and an open MRI machine .

Why It Is Done

Magnetic resonance imaging (MRI) of the shoulder is done to:

• Check unexplained shoulder pain.
• Find problems in the shoulder, such as arthritis, bone tumors, worn-out cartilage, torn ligaments, torn tendons, or infection. An MRI can detect tears in the cartilage (labrum) in the shoulder. Labral tears often are caused by injury and can lead to shoulder pain.
• Find rotator cuff disorders, including tears and impingement.

MRI may also help diagnosis a bone fracture when X-rays and other tests are not clear. MRI is done more commonly than other tests to check for certain bone and joint problems.

How To Prepare

Before your MRI test, tell your health professional and the MRI technologist if you:

• Are allergic to any medicines. The contrast material used for MRI does not contain iodine. If you have a known allergy to the contrast material used for MRI, tell your health professional before having the test. Sometimes the benefits of having this test may outweigh the risks.
• Are or might be pregnant.
• Have metal screws in your shoulder from a past shoulder surgery.
• Have a pacemaker, artificial limb, any metal pins or metal parts in your body (especially in the eyes), metal heart valves, metal clips in your brain, metal implants in your ear, tattooed eyeliner, or any other implanted or prosthetic medical device (such as a medicine infusion pump). If you have had an accident or you work around metal, there is a possibility that you have metal fragments in your head, eyes, skin, or spine. An X-ray may be taken before the MRI to see if you can have the test.
• Had recent surgery on a blood vessel. In some cases you may not be able to have the MRI test.
• Have an intrauterine device (IUD) in place. An IUD may prevent you from having the MRI test done.
• Become very nervous in confined spaces. You need to lie very still inside the MRI magnet, so you may need to have the test done with open MRI equipment. It is not as confining as standard MRI machines. You may need medicine to help you relax.
• Have any other health conditions, such as kidney problems or sickle cell anemia, that may prevent you from having an MRI using contrast material.
• Wear any medicine patches. The MRI may cause a burn at the patch site.

You may need to sign a consent form that says you understand the risks of a shoulder MRI and agree to have the test done. Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form (What is a PDF document?) .

You may need to arrange for someone to drive you home after the test, if you are given a medicine (sedative) to help you relax.

How It Is Done

A magnetic resonance imaging (MRI) test is usually done by an MRI technologist. The resulting pictures are usually interpreted by a radiologist. However, some other types of doctors, such as an orthopedic surgeon, can also interpret a shoulder MRI scan.

You will need to remove all metal objects (such as hearing aids, dentures, jewelry, watches, and hairpins) from your body because these objects may be attracted to the powerful magnet used for the test.

You will need to take off all or most of your clothes, depending on which area is examined (you may be allowed to keep on your underwear if it is not in the way). You will be given a gown to use during the test. If you are allowed to keep some of your clothes on, you should empty your pockets of any coins and cards (such as credit cards or ATM cards) with scanner strips on them because the MRI magnet may erase the information on the cards.

During the test, you will lie on your back on a table that is part of the MRI scanner. The table will slide into the space that contains the magnet. A device called a coil may be placed over or wrapped around the area to be scanned.

Some people feel nervous (claustrophobic) inside the MRI magnet. If feeling nervous keeps you from lying still, you can be given a medicine (sedative) to help you relax. Some MRI machines (called open MRI) are made so that the magnet does not enclose your entire body. Open MRI machines may be helpful if you are claustrophobic.

Inside the scanner, you will hear a fan and feel air moving. You may also hear tapping or snapping noises as the MRI scans are taken. You may be given earplugs or headphones with music to reduce the noise. It is very important to hold completely still while the scan is being done. You may be asked to hold your breath for short periods of time.

During the test, you may be alone in the scanner room. However, the technologist will watch you through a window. You will be able to talk with the technologist through a two-way intercom.

If contrast material is needed, the technologist will put it in an IV in your arm. The injection may be given over 1 to 2 minutes.

Contrast material may be put directly into your shoulder joint by the radiologist. Your doctor will make your shoulder numb (local anesthetic) before putting in the contrast material. Then more MRI scans are done for this part of the test. This is called a magnetic resonance arthrogram.

An MRI test usually takes 30 to 60 minutes but can take as long as 2 hours.

How It Feels

You won't have pain from the magnetic field or radio waves used for the MRI test. The table you lie on may feel hard and the room may be cool. You may be tired or sore from lying in one position for a long time.

If a contrast material is used, you may feel some coolness and flushing as it is put into your IV. You may have a squishy feeling in your shoulder for 1 to 2 days from the material.

In rare cases, you may feel:

• A tingling feeling in the mouth if you have metal dental fillings.
• Warmth in the area being examined. This is normal. Tell the technologist if you have nausea, vomiting, headache, dizziness, pain, burning, or breathing problems.

Risks

There are no known harmful effects from the strong magnetic field used for MRI. However, the magnet is very powerful. The magnet may affect pacemakers, artificial limbs, and other medical devices that contain iron. The magnet will stop a watch that is close to the magnet. Any loose metal object has the risk of causing damage if it gets pulled toward the strong magnet.

Metal parts in the eyes can damage the retina. If you may have metal fragments in the eye, an X-ray of the eyes may be done before the MRI. If metal is found, the MRI will not be done.

Iron pigments in tattoos or tattooed eyeliner can cause skin or eye irritation.

An MRI can cause a burn with some medicine patches. Be sure to tell your health professional if you are wearing a patch.

There is a slight chance of an allergic reaction if contrast material is used during the MRI. However, most reactions are mild and can be treated using medicine. There also is a slight risk of an infection at the IV site.

Results

Magnetic resonance imaging (MRI) is a test done with a large machine that uses a magnetic field and pulses of radio wave energy to make pictures of the shoulder.

The radiologist may discuss preliminary results of the MRI with you right after the test. Complete results are usually available for your health professional in 1 to 2 days.

An MRI scan can sometimes find a problem in a tissue or organ, even when the size and shape of the tissue or organ looks normal.

What Affects the Test

Factors that can interfere with your test or the accuracy of the results include:

• Metal devices in your shoulder or chest from previous surgery. These can make the MRI pictures blurry and prevent your doctor from seeing what is wrong with your shoulder.
• Pregnancy. An MRI test usually is not done during pregnancy.
• Medical devices that use electronics, such as a pacemaker or medication infusion pump. The MRI magnet may cause problems with these devices.
• Inability to remain still during the test.
• Obesity. A person who is very overweight may not fit into the opening of some standard MRI machines.

Many modern medical devices that do not use electronics, such as heart valves, stents, or clips, can be safely placed in most MRI machines. But some newer MRI machines have stronger magnets. The safety of MRI scans with these stronger MRI magnets in people with medical devices is not completely known.

What To Think About

• Sometimes your MRI test results may be different than those from CT, ultrasound, or X-ray tests because the MRI scan is more specific.
• Other procedures, such as an arthrogram or arthroscopy, may be used to evaluate shoulder problems. For more information, see the medical tests Arthrogram or Arthroscopy.
• Open MRI machines are now made so that the magnet does not completely surround you. Open MRI is useful for people who are claustrophobic or obese. But these machines are not available everywhere. Also, these machines may not be able to do all the studies needed to check for problems.
• Contrast material that contains gadolinium may cause a serious skin problem (called nephrogenic fibrosing dermopathy) in people with kidney failure. Tell your doctor if you have serious kidney disease before having an MRI scan.

References

Other Works Consulted

• Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2006). Mosby's Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.

Credits