MR Imaging (MRI) - Musculoskeletal

MR Imaging (MRI) - Musculoskeletal

• What is MRI of the Musculoskeletal System?
• What are some common uses for Musculoskeletal MRI?
• How is the MRI performed?
• Who interprets the results and how do I get them?
• What are the limitations of Musculoskeletal MRI?
• What are the benefits vs. risks?

What is MRI of the Musculoskeletal System?

Magnetic resonance imaging (MRI) uses radio waves and a strong magnetic field rather than x-rays to provide clear and detailed pictures of internal organs and tissues. The parts of the musculoskeletal system that are most frequently imaged with MRI are the spine, knee and shoulder. However, MRI has also been used to study almost every joint in the body including the hips, wrists, and hands. MRI requires specialized equipment and expertise and allows evaluation of some body structures that may not be as visible with other imaging methods.

What are some common uses of Musculoskeletal MRI?

Because MRI can give such clear pictures of soft tissue structures near and around bones, it is usually the best choice for examination of the body's major joints, the spine for disk disease and soft tissues of the extremities. MRI is widely used to diagnose sports-related injuries, as well as work-related disorders caused by repeated strain, vibration or forceful impact. Using MRI images, physicians can locate and identify the cause of pain, swelling or bleeding in the tissues in and around the joints and bones. The images allow the physician to clearly see even very small tears and injuries to tendons, ligaments and muscles and even some fractures that cannot be seen on x-rays. In addition, MRI images can give physicians a clear picture of degenerative disorders such as arthritis, deterioration of joint surfaces, or a herniated disk. Neurosurgeons often use MRI to evaluate the integrity of the spinal cord after trauma. Finally, MRI is also useful for the diagnosis and characterization of infections (osteomyelitis for example) and tumors (metastases for example) involving bones and joints.

How is the MRI performed?

The patient is placed on a sliding table and a radio antenna device called a surface coil is positioned around the part of the body to be imaged. After positioning the patient inside the MRI gantry, the technologist leaves the room and the individual MRI sequences are performed. The patient will hear tapping noises during the exam. The tapping is created when magnetic field gradient coils are switched on and off. The patient is able to communicate with the technologist at any time using an intercom. Also, a friend or, if a child is being examined, a parent may stay in the room. Depending on how many images are needed the exam will generally take 15 to 45 minutes, although a very detailed study may take longer. You will be asked not to move during the actual imaging process, but between sequences some movement is allowed. Patients are generally required to remain still for only a few seconds to a few minutes at a time. Some patients will require an injection of a contrast material to enhance the visibility of certain tissues or blood vessels. The contrast material is injected about two-thirds of the way through the exam. A small needle connected to an intravenous line is placed in an arm or hand vein for the injection. If you are having you shoulder, knee, or other specifice joint imaged an intra-articular injection of contrast maybe required. The injection is performed either prior to, or about half-way through the exam (please see section on “MRI Arthrography” for details).

When the exam is over the patient is asked to wait until the images are examined to determine if more images are needed.

Who interprets the results and how do I get them?

A musculoskeletal radiologist, who is a physician experienced in spine and jointMRI, will analyze the images and send a signed report with his or her interpretation to the patient's personal physician. The personal physician's office will inform the patient on how to obtain their results. New technology also allows for distribution of diagnostic reports and referral images over the Internet at some facilities.

What are the limitations of Musculoskeletal MRI?

Bone is better imaged by conventional x-rays, and CT is preferred for patients with severe bleeding, acute trauma or who because of their medical condition are unable to tolerate an MR scan procedure. MRI may not always distinguish between tumor tissue and edema fluid and does not detect calcium when this is present within a tumor. In most cases the exam is safe for patients with metal implants but there are a few exceptions, so patients should inform the technician of an implant prior to the test. The exam must be used cautiously in early pregnancy. MRI often costs more than CT scanning.

What are the benefits vs. risks?

Benefits:

• MR images of the soft tissue structures of the body such as the muscles, tendons, joints and blood vessels, are clearer and more detailed than with other imaging methods.

• MR images can help identify the causes of pain, swelling and bleeding so that appropriate
treatment can begin.

• MRI contrast material is less likely to produce an allergic reaction than the iodine-based materials used for conventional x-rays and CT scanning.

• MRI enables the detection of abnormalities, injuries and diseases that might be obscured by bone tissue with other imaging methods.

• MRI provides a fast, noninvasive way to assess a variety of muscle and joint injuries and
disorders.

• The detail of MR images makes them an invaluable tool in early diagnosis and evaluation of tumors.

• Exposure to radiation is avoided.

Risks:

• There are no definite side effects from any type of MRI study, including MR angiography.

• An undetected metal implant may be affected by the magnetic field. The procedure should be avoided in any patient with a pacemaker, implanted neurostimulator, certain types of metallic ear implants(cochlear implants) or metallic object within the eye socket. It should also be avoided if the patient has a port for delivering insulin or chemotherapy (however, many ports are detachable so patients can safely undergo MRI examinations).

• MRI is generally avoided in the first 12 weeks of pregnancy. Doctors usually use other methods of imaging, such as ultrasound, on pregnant women unless there is a strong medical reason.

• Women who are breast-feeding should inform the radiologist and ask how to proceed. If necessary they may pump breast milk before the exam for use until the gadolinium contrast material has cleared from the body.

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