Procedure of the examination
The course of the MRI examination usually begins with an informative conversation with the respective specialist. Preparations at home are usually not necessary, but care should be taken to ensure that there is no more fluid and food intake approximately four hours before the examination. Since contrast media are often used in shoulder MRI examinations to improve imaging, the patient is kept fasting in case of a very rare reaction with nausea and vomiting.
In shoulder MRI examinations, there is often an exception to the rule that contrast medium is given in advance of the actual examination for better evaluation. The patient is injected with the contrast medium either via the vein (indirect arthrography) or into the shoulder joint itself (direct arthrography) approximately 10 minutes before the examination begins. The patient is then asked to move the shoulder joint for 10 minutes.
After partially undressing and removing ALL metal objects from the body, the patient lies supine on a flat examination couch, which is then pushed into the MRI machine for the examination period of about 20 minutes (during the shoulder examination, the head is also in the machine). In order to shield the patient from the loud knocking noise during the examination, the patient is usually also given headphones. Furthermore, the patient holds a so-called emergency button in one hand, which can be pressed at any time in case of problems or complications.
During an MRI examination of the shoulder it is not necessary to be strictly fasting (strictly fasting means no intake of fluids or food after 10 p.m. the day before the examination). Only from 4 hours prior to the imaging should food and fluid intake be avoided. The reason for this is that during the MRI examination it may be necessary to inject contrast medium.
This rarely leads to an intolerance reaction with nausea and vomiting, in which case an empty stomach eases the situation. Only special MRI examinations of the gastrointestinal tract require an absolute or strict fasting prior to the examination. Since strong magnetic fields are generated during an MRI examination, it is important that no metal objects get into or near the examination device.
The extent to which the patient is urged to take off their clothes therefore depends on whether there are any metallic objects (buttons, zipper, bra underwires, etc.) on the respective items of clothing. During the MRI examination of the shoulder, a T-shirt or undershirt can usually be left on, but women in particular are asked to take off the bra underneath.
Here the time of preparation is not included. In case of a special examination, however, it can take 30 to 60 minutes until the examination is completed. After the examination, the MRI images are printed out or burned onto a CD and then discussed with the patient.
Depending on the extent of the disease, this also takes about 30 minutes. It is recommended to take about 1 1⁄2 to 2 hours for the entire scope of the examination. The duration of an MRI of the shoulder joint depends more on the procedures within the radiology department than on the speed of the MRI machine.
Whether contrast media are used always depends on which structures in the shoulder joint are to be examined by MRI. There are two ways to administer contrast media. On the one hand, the contrast medium can be administered into the vein.
However, it is better to administer the contrast medium directly into the joint, which delays the duration of the MRI and is associated with a higher risk of infection. Contrast medium is injected mainly when one wants to examine. Contrast medium is also required for the assessment of the bursa above the rotator cuff with regard to bursitis of the shoulder (subacromial bursitis).
The contrast medium is injected into the arm through a vein, thus increasing the tissue contrast. As a rule, the contrast media are well tolerated.They do not contain iodine and are not chemically similar to the contrast media used in X-ray examinations, so they can also be used in cases of allergy to X-ray contrast media. They are excreted in the urine after only a few hours. Contrast media are also used to examine the cartilage bulge (labrum) around the joint socket and joint cartilage. In contrast, the examination without contrast medium is used for the following structures:
- Partial tears or tears of the tendons of the rotator cuff or
- The long biceps tendons
- In case of a tumor of the soft tissues,
- With a fracture,
- In case of a change of the joint and
- In case of a joint infection.