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CT & MR Arthrography
Arthrography is medical imaging to evaluate conditions of joints. There are several methods to do this.
Conventional arthrography is the x-ray examination of a joint that uses a special form of x-ray called fluoroscopy and a contrast material containing iodine. Alternate methods of arthrography examinations use magnetic resonance imaging (MRI) or computed tomography (CT).
Fluoroscopy makes it possible to see bones, joints and internal organs in motion. When iodine contrast is injected into the joint, it fills the entire joint and appears bright white on an arthrogram, allowing the radiologist to assess the anatomy and function of the joint. Although the injection is typically monitored by fluoroscopy, the examination also involves taking radiographs for documentation. The images are most often, but not always, stored or viewed electronically.
MR arthrography also involves the injection of a contrast material into the joint, just like in conventional arthrography, except that the MR contrast material is different and contains gadolinium, which affects the local magnetic field. As in conventional arthrography, the contrast material outlines the structures within the joint and allows them to be evaluated by the radiologist.
MRI uses a powerful magnetic field, radiofrequency pulses and a computer to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures. MRI does not use ionizing radiation (x-rays).
CT arthrography uses the same type of contrast material as conventional arthrography and may be supplemented by air to produce a double contrast CT arthrogram. CT makes cross sectional images processed by a computer using x rays.
Arthrographic images help physicians evaluate alterations in structure and function of a joint and help to determine the possible need for treatment, including arthroscopy, open surgery or joint replacement. The procedure is most often used to identify abnormalities within the:
The procedure is also used to help diagnose persistent, unexplained joint pain or discomfort. Arthrography is particularly effective for detecting tears or lesions of the structures and ligaments of the joints, especially the knee, wrist and elbow, as well as rotator cuff tears or damage from a shoulder dislocation.
No special preparation is necessary before arthrography. Food and fluid intake do not need to be restricted, unless a sedative will be given.
You should inform your physician of any medications you are taking and if you have any kidney problems or allergies, especially to iodinated contrast materials. Also inform your doctor about recent illnesses or other medical conditions.
Some MRI examinations may require the patient to receive an injection of contrast into the bloodstream. The radiologist or technologist may ask if you have allergies of any kind, such as allergy to iodine or x-ray contrast material, drugs, food, the environment, or asthma. However, the contrast material used for an MRI exam, called gadolinium, does not contain iodine and is less likely to cause side effects or an allergic reaction.
The radiologist should also know if you have any serious health problems or if you have recently had surgery. Some conditions, such as severe kidney disease, may prevent you from being given contrast material for having an MRI.
If you are scheduled to have MR or CT arthrography and have claustrophobia (fear of enclosed spaces) or anxiety, you may want to ask your physician about being sedated prior to the scheduled examination.
Jewelry and other accessories should be left at home if possible, or removed prior to the MRI scan. Because they can interfere with the magnetic field of the MRI unit, metal and electronic objects are not allowed in the exam room. These items include:
- jewelry, watches, credit cards and hearing aids, all of which can be damaged.
- pins, hairpins, metal zippers and similar metallic items, which can distort MRI images.
- removable dental work.
- pens, pocketknives and eyeglasses.
- body piercings.
In most cases, an MRI exam is safe for patients with metal implants, except for a few types. People with the following implants cannot be scanned and should not enter the MRI scanning area unless explicitly instructed to do so by a radiologist or technologist who is aware of the presence of any of the following:
- internal (implanted) defibrillator or pacemaker
- cochlear (ear) implant
- some types of clips used on brain aneurysms
- some types of metal coils placed within blood vessels
You should tell the technologist if you have medical or electronic devices in your body, because they may interfere with the exam or potentially pose a risk, depending on their nature and the strength of the MRI magnet. Examples include but are not limited to:
- artificial heart valves
- implanted drug infusion ports
- implanted electronic device, including a cardiac pacemaker
- artificial limbs or metallic joint prostheses
- implanted nerve stimulators
- metal pins, screws, plates, stents or surgical staples
In general, metal objects used in orthopedic surgery pose no risk during MRI. However, a recently placed artificial joint may require the use of another imaging procedure. If there is any question of their presence, an x-ray may be taken to detect the presence of and identify any metal objects.
Patients who might have metal objects in certain parts of their bodies may also require an x-ray prior to an MRI. You should notify the technologist or radiologist of any shrapnel, bullets, or other pieces of metal which may be present in your body due to accidents. Dyes used in tattoos may contain iron and could heat up during MRI, but this is rarely a problem. Tooth fillings and braces 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.
You may be asked to remove some or all of your clothes and to wear a gown during the exam. You may also be asked to remove jewelry, removable dental appliances, eye glasses and any metal objects or clothing that might interfere with the x-ray images.
Women should always inform their physician and x-ray technologist if there is any possibility that they are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to radiation. If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the baby. Though MRI does not use ionizing radiation, women should still inform their physician and technologist if they may be pregnant.