X-Rays, Imaging, and MRI
As part of your initial evaluation for rheumatoid arthritis, your doctor may have x-rays taken of your joints. X-rays can reveal certain signs of inflammation and damage (joint erosion) that are indicative of RA. Other imaging tests that may be useful in the diagnosis of RA, include magnetic resonance imaging (MRI) and ultrasound.1
How will x-rays help my doctor diagnose RA?
Typically, your doctor will take x-rays of joint in your hands, wrists, and feet. These joints usually show the earliest signs of RA.
In some patients, early x-ray results will show the signs of joint damage that is common with RA. For most patients, joint changes will only become apparent over time. Early joint changes visible on x-ray may include only swelling of soft tissues and signs of a decrease in bone mineral density (osteopenia).1
In addition to helping your doctor determine a diagnosis of RA, early x-ray images will also provide a baseline to compare with later x-ray results, to monitor the progression of RA.1
Use of magnetic resonance imaging (MRI) in RA
Magnetic resonance imaging (MRI) is a more sensitive imaging technique than an x-ray. An MRI is more useful in detecting changes to joints and tissues that resulted from inflammation. MRIs also detect joint damage earlier than traditional x-rays. One study showed that an MRI revealed more bony erosions in the hand than an x-ray.
In addition, MRIs are useful in detecting the thickening of synovial tissue that occurs with RA and swelling of bone marrow that predicts later bone erosion.1,3
What should I expect when I get an MRI?
An MRI scanner is typically an enclosed cylindrical tube into which the patient is inserted for scanning. Newer MRI scanners do not require complete insertion into the scanning tube.
Also, some MRI facilities have scanners that are open on both sides. However, these types of scanners tend not to give the same level of clarity as an MRI scanner with an enclosed chamber.
When you receive an MRI, you’ll be placed on a table that will be rolled into the cylindrical MRI tube. You’ll be able to speak with the MRI technician during your MRI should you need any assistance.
An MRI typically takes 20 to 45 minutes. You will be asked to remain motionless for a period of time, lasting anywhere from several seconds to several minutes. If you tend to get claustrophobia (intense fear of tight or crowded spaces), tell your physician. You may be able to get a sedating medication before the MRI scan. If you don’t like enclosed spaces and would prefer not to get sedation, ask your physician if an open-sided MRI scanner is an option.
Gadolinium-based agents help doctors see MRI images clearer. If your physician has ordered a gadolinium (Gd, for short) enhancement for your MRI, staff at the MRI facility will give you the gadolinium by placing an intravenous needle in your vein before the MRI.
As MRI does not rely on radiation for imaging, it is a safer imaging technique than computed tomography (CT).
How does an MRI work?
MRI creates a powerful magnetic field and radio waves to manipulate the position of hydrogen protons within your body. As the protons change position, they give off signals that can be picked up by the MRI scanner. These signals can be used by a computer to make an image of any tissue that is being scanned. Different tissues in the body contain various amounts of water and therefore more hydrogen. As a result, MRI images allow you to see the differences in these tissues.4
Use of ultrasonography in RA
Ultrasonography (ultrasound, for short) provides another form for imaging and measuring joint involvement in RA. In a study comparing ultrasound and MRI to detect joint inflammation in RA, the results of the ultrasound were similar to an MRI in about 75 percent of cases.1
Ultrasound provides some advantages over MRI. An ultrasound can be performed easily in the office. Results are available immediately, so adjustments to treatment can be made often during the same office visit. Additionally, ultrasound can be useful in guiding joint fluid aspiration and injections directly into the joint.5