Definition and Overview
Magnetic resonance imaging (MRI) of shoulders is a non-invasive imaging test that provides detailed information about the structures of the shoulder, including the bones, joints, muscles, ligaments, and tendons. It can be helpful in diagnosing a condition, treating an injury, managing a disease, or confirming doctor’s suspicions, among others.
The test uses strong magnetic fields and radio frequency pulses to create images that are processed and stored in a computer for review and interpretation.
The shoulders are some of the most complicated parts of the body. Each is composed of three different bones: clavicle (collarbone), which provides stability to the movements of the shoulders; humerus, which is the biggest bone in the arm; and scapula (shoulder blade).
These bones, along with the chest bone (sternum), create the joints of the shoulders, namely, sternoclavicular, acromioclavicular, and glenohumeral. The shoulders also have tendons, ligaments, cartilages, and muscles. These parts are all susceptible to a variety of conditions, health issues, and injury.
The MRI is performed to help the doctor assess the condition of the shoulder in relation to a particular symptom, condition, or injury.
Who Should Undergo and Expected Results
An MRI of the shoulders is an effective tool in diagnosing problems affecting the rotator cuff, a group of small muscles that keep the shoulder joints stable and in place. The muscles may be torn or experience wear due to old age, condition, or injury. This can lead to more problems and tearing of the muscles. Often, an MRI is recommended if other types of non-invasive tests like ultrasound and X-ray cannot provide sufficient and accurate information for the attending physician to make a diagnosis.
The test may also be recommended for people who have:
- Swelling or inflammation (the shoulder may be sore, red, and tender to touch)
- Degenerative disease
- Injury related to an accident (e.g., fall, vehicular collision, or slip) as well as sports
- Infection affecting any part of the shoulder
- Injury due to repetitive use
- Tumor growth
The MRI may also be conducted for management—that is, to determine the success of a shoulder surgery or cancer treatment, to name a few.
The test normally runs for 20 to 30 minutes, although it may extend to at least an hour, maybe more, depending on the preparation and the kinds of images the radiologist needs. It can be carried out in an outpatient or inpatient setting. A radiologist is the one that interprets the results, although a doctor with adequate radiologic training can also do the job. Either way, the patient’s doctor is the one in charge of relaying the results as he or she needs to corroborate it with the other test results and consultation notes.
How Does the Procedure Work?
Many people tend to confuse MRI with PET and CT scans. All of them have different functions and uses different technologies. The CT scan is the closest rival of MRI, but they vary in terms of accuracy.
An MRI is a machine with a magnetic field that emits radiofrequency waves. The body reacts to the pulses and the magnetic field since it is composed of a variety of molecules and atoms, inside of which is a proton, which is reactive to the magnetic field. The reaction of the protons helps create the images needed for the MRI.
The test doesn’t require any special preparation such as diet. However, if the MRI test uses a contrast material, the patient may have to undergo a series of examinations including kidney function test. The patient should also inform the radiologist if he or she is prone to allergic reactions to dyes.
The scan is safe for many people. It can even be carried out on infants and children, but they may have to be administered with general anesthesia to keep them still during the entire examination. Patients who are claustrophobic may also be sedated. They can also use an open MRI machine, although this is not yet available in several hospitals.
The test is not ideal for people with certain types of implants like cochlear, pacemakers scans, and defibrillators. The patient should discuss this with the doctor and the radiologist before the procedure begins.
If a contrast material is to be used, an IV line will be attached to the arm to allow the dye to enter the bloodstream. The patient may have to wait for a couple of minutes before the exam officially begins.
The MRI contains a movable table, where the patient lies comfortably in a hospital gown or loose-fitting clothing. Sometimes it can be cold, so the patient may request for a blanket provided that it doesn’t interfere with the shoulder areas. The patient lies still while the technician, who’s found in another room, focuses the magnetic field on the shoulders to start obtaining photos. Instructions are delivered through the microphone.
After the test is done, the patient can return to regular activities. Those with contrast dye may be requested to drink a lot of fluids to flush the dye out.
Possible Risks and Complications
In general, MRI scan of the shoulders is safe and painless. Some patients, however, may develop claustrophobia due to the nature of the structure that can escalate to a panic attack and hyperventilation. There are also patients who cannot be provided with a contrast dye because of possible allergic reactions.
MRI can be performed on pregnant women, but it’s not recommended to those on their first trimester.
Wilkinson ID, Paley MNJ. Magnetic resonance imaging: basic principles. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 5.
DeLee JC, Drez D Jr, Miller MD, eds. DeLee and Drez's Orthopaedic Sports Medicine. 3rd ed. Philadelphia, PA: Saunders Elsevier; 2009:chap 17.