X-Rays, Imaging, and MRI

As part of your initial evaluation for RA, your doctor may have x-rays taken of your joints. X-rays can reveal certain signs of joint involvement (inflammation) and damage (bone erosion) that are indicative of RA. Other imaging tests that may be useful in 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 your hands, wrists, and feet, the joints that usually show the earliest signs of involvement in RA. In some patients with RA, early x-ray results will show the beginnings of joint erosion characteristic of the disease. However, for most patients joint changes will only become evident 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

MRI is a more sensitive imaging technique than plain x-ray and more useful in detecting changes to joints and related structures resulting from inflammation. It can also detect joint damage earlier than traditional x-rays. In one study MRI was compared with x-ray and revealed seven times as many bony erosions in the hand than plain x-rays. MRI is 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. However, there are newer MRI scanners that 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 at all times during your MRI should you need assistance of any kind. An MRI typically takes approximately 20 to 45 minutes and 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, tell your physician and you can arrange to get a sedating medication before the MRI scan. If you don’t like enclosed spaces (many people don’t) and would prefer not to get sedation, ask your physician if he or she thinks an open-sided MRI scanner is a possibility for you.

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), another imaging technology.


How does an MRI work?

MRI creates a powerful magnetic field, as well as 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 whatever tissue is being scanned. Because some tissues in the body contain more water (and therefore more hydrogen) than others, the MRI images allow you to see the differences in these tissues.4


Use of ultrasonography in RA

In addition to x-ray and MRI, ultrasonography (or ultrasound for short) provides another alternative for imaging and measuring joint involvement in RA. In a study comparing use of ultrasound and MRI to detect joint inflammation in RA, results of ultrasound agreed with those of MRI in about 75% of cases.1

Ultrasound provides some advantages over MRI. It 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

Written by: Jonathan Simmons | Last reviewed: September 2013.
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