Joint (Musculoskeletal) Imaging

What to expect with your procedure

Because the strong magnetic field used for MRI will pull on any metal object implanted in the body, MRI staff will ask whether you have a prosthetic hip, heart pacemaker (or artificial heart valve), implanted port, infusion catheter (brand names Port-o-cath, Infusaport, Lifeport), intrauterine device (IUD) or any metal plates, pins, screws or surgical staples in your body. Tattoos and permanent eyeliner may also create a problem. You will be asked if you have ever had a bullet or shrapnel in your body or ever worked with metal. If there is any question of metal fragments, you may be asked to have an x-ray that will detect any such metal objects. Tooth fillings usually are not affected by the magnetic field, but they may distort images of the facial area or brain, so the radiologist should be aware of them. The same is true of braces, which may make it hard to "tune" the MRI unit to your body. You will be asked to remove anything that might degrade MRI images of the head, including hairpins, jewelry, eyeglasses, hearing aids and any removable dental work.

The radiologist or technologist may ask about drug allergies and whether head surgery has been done in the past. If you might be pregnant, this should be mentioned. Some patients who undergo MRI of the head in an enclosed unit may feel confined or claustrophobic. If you are not easily reassured, a sedative may be administered. Roughly one in 20 patients will require medication.

Preparing for your procedure

The patient is placed on a sliding table and a radio antenna device called a surface coil is positioned around the upper part of the head. After positioning the patient with the head inside the MRI gantry, the radiologist and technologist leave the room and the individual MRI sequences are performed. The patient is able to communicate with the radiologist or technologist at any time using an intercom. Also, many MRI centers allow a friend or, if a child is being examined, a parent into 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. The patient 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 at a time. Some patients will require an injection of a contrast material to enhance the visibility of certain tissues or blood vessels. A small needle connected to an intravenous line is placed in an arm or hand vein. A saline solution will drip through the intravenous line to prevent clotting until the contrast material is injected about two-thirds of the way through the exam.

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

MRI causes no pain, but there may be a feeling of claustrophobia from being closed-in or from the need to remain still. You may notice a warm feeling in the area under examination; this is normal, but if it bothers you the radiologist or technologist should be told. If a contrast injection is needed, there may be discomfort at the injection site, and you may have a cool sensation at the site during the injection. Most bothersome to many patients are the loud tapping or knocking noises heard at certain phases of imaging. Ear plugs may help. When the knocking and the slight vibration that may accompany it stops, you can reposition your arms.