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 an MRI gives information about structures in the body that can't 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. An 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.

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 (I.V.) in your arm or directly into your shoulder joint.

You may be able to have an MRI with an open machine that doesn't enclose your entire body. But open MRI machines aren't available everywhere. The pictures from an open MRI may not be as good as those from a closed 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 diagnose 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

In general, there's nothing you have to do before this test, unless your doctor tells you to.

Tell your doctor if you get nervous in tight spaces. You may get a medicine to help you relax. If you think you'll get this medicine, be sure you have someone to take you home.

How It Feels

You won't have pain from the magnetic field or radio waves used for the MRI test. But 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 when it is put into your I.V.

In rare cases, you may feel:

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

Risks

There are no known harmful effects from the strong magnetic field used for an MRI. But the magnet is very powerful. It may affect any metal implants or other medical devices you have.

Risks from contrast material

Contrast material that contains gadolinium may be used in this test. But for most people, the benefit of its use in this test outweighs the risk. Be sure to tell your doctor if you have kidney problems or are pregnant.

There is a slight chance of an allergic reaction if contrast material is used during the test. But most reactions are mild and can be treated using medicine.

If you breastfeed and are concerned about whether the contrast material used in this test is safe, talk to your doctor. Most experts believe that very little dye passes into breast milk and even less is passed on to the baby. But if you are concerned, you can stop breastfeeding for up to 24 hours after the test. During this time, you can give your baby breast milk that you stored before the test. Don't use the breast milk you pump in the 24 hours after the test. Throw it out.

Results

The radiologist may discuss early results of the MRI with you right after the test. Complete results are usually ready for your doctor 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.

Magnetic resonance imaging (MRI) of the shoulder

Normal:

• The muscles, tendons, bones, and joints look normal in size, shape, and location.
• No growths, such as tumors, are present.
• No cartilage problems or tears, broken bones (fractures), or loose bodies are present.
• No rotator cuff injury or tear is present.
• No signs of inflammation or infection are present.

Abnormal:

• A growth, such as a tumor, inflammation, or infection in the bone or joint, is present.
• A collection of fluid is found, which could mean you have an infection.
• Damage to ligaments, tendons, or cartilage is present.
• Joint damage is present, and bones may show signs of disease or fracture.