What is an MRI?
An MRI examination is a special machine (big magnet) that uses strong magnetic fields and radio waves to produce detailed images of the shoulder. MRI is very useful when there is a significant shoulder joint injury (for example, shoulder dislocation) and suspicion of injuries to the ligaments, tendons, bones and internal structures within the shoulder joint.
What does a shoulder MRI scan involve?
A shoulder MRI scan will involve you staying still for approx. 20-30 minutes inside a special machine (small tunnel) while the images are taken. It can be slightly noisy while you are inside the machine therefore, ears protection or headphone with music will be used while you are inside the scanner. The imaged body part (the shoulder) will be put inside a small plastic device (called the coil). This is very useful to obtain detailed images of the shoulder joint. The technician will see you before the scan to ensure that you do not have any metallic objects before going into the scanner. This can be dangerous as the scanner has a strong magnet, and any small metallic object can become a projectile.
Is it safe to have a shoulder MRI scan?
An MRI scan is very safe and routinely performed nowadays with very few contraindications. The technician will ask you all the relevant questions to make sure that it is safe for you to undergo an MRI before your appointment. Generally, if you have a metallic object inside your body, an MRI scan might not be safe for you. The MRI may result in the movement of small metallic objects within the body, which can cause tissue damage if it is in a sensitive area (like in the brain or eye). Usually, there is no problem with big metallic objects (like joint replacements) if the surgery is not recent, as they will be well-fixed within the body. Some examples of conditions where you should not go inside an MRI machine scanner include:
· If you have a metallic foreign body within your eye. This is especially seen in welders. An x-ray might be needed before the examination to ensure no significant metallic foreign body near your eyes.
· Surgical clips inside your brain.
· Cochlear (ear) implant.
· A heart pacemaker or defibrillator.
· Recent surgery (within 6 weeks from the scan), especially if it involves inserting a sizeable metallic object into the body (like a joint replacement).
What are the different types of MRI machines, and which one is better for me?
The newer generations of MRI are called (3T or 3 Tesla) while the older ones are called 1.5T scanners. This refers to the strength of the main magnet of the scanner. Stronger magnets usually result in better images and, therefore, can provide a superior assessment of the imaged body part. However, this is not a hard rule, and excellent images can still be obtained using 1.5T scanners. Scanners can also be divided according to the body part they can image into a body or extremity scanners. The latter are smaller, with weaker magnets and can only image the extremities. Body scanners are larger, with stronger magnets and can image any body part. The images produced by body scanners are usually superior (because they have stronger magnets and the imaging field is usually more homogenous). These are usually preferred when you are getting a shoulder MRI.
What shoulder problems will be picked up on an MRI scan?
Generally, MRI is a very good scan to diagnose shoulder problems. It is very important for the scan to be interpreted/read by a specialist musculoskeletal radiologist to correlate the clinical and radiological findings and reach the correct diagnosis. The shoulder conditions that can be assessed on an MRI examination include:
Below is another MRI examination showing subacromial shoulder bursitis
What are the disadvantages of an MRI examination?
A shoulder MRI examination has a few drawbacks
· Usually, they are costly compared to other types of scans.
· They require you to stay still for 20-30 minutes; otherwise, the images will not be clear.
· People who are not comfortable with small spaces (claustrophobic) may find it difficult to have an MRI scan
· It may be unsafe to perform in the few situations explained above.
How much does a shoulder MRI cost?
This varies depending on the institution. In the UK, the price can range from £300 to £800.
Shoulder MRI vs Shoulder x-ray and ultrasound scan
A knee X-ray (or knee radiograph) is a black-and-white image produced by sending an X-ray beam through the area and getting the images on a film. It is usually the first type of imaging done when there is suspicion of a shoulder problem, like shoulder arthritis or bony injury. Unlike MRI, X-rays cannot assess the soft tissues. To find out more, please see our article about shoulder X-rays.
Ultrasound is high-frequency sound waves produced by a special machine and can provide useful images of the tissues within the body. To find out more, please see our article about shoulder ultrasound. Ultrasound is the preferred imaging choice when a shoulder injection is required. Ultrasound allows for direct visualisation of the needle to ensure medicines are injected into the exact targeted site. There is significant evidence that ultrasound-guided injections provide better levels of pain relief and longer effects compared with injections done without imaging guidance. A shoulder ultrasound examination is very useful to assess for the following conditions and guide the procedures below:
Shoulder conditions and treatments
