Imaging tests such as X-rays, magnetic resonance imaging, and ultrasound are important tools for diagnosing and treating rheumatoid arthritis. RA is an autoimmune disease that can inflame joint tissue. One of the hallmark RA symptoms is the presence of pain or limited mobility in the joints. Imaging tests are helpful not only to detect the condition, but also to look for ongoing issues such as bone erosion. Imaging is one important part of an early diagnosis and treatment of RA.
There isn't a single test to determine if someone has RA, and imaging is only one piece of the overall diagnostic puzzle. Physicians also rely on family history, discussion of symptoms, physical examinations, and blood tests that look for issues such as elevated C-reactive protein levels. Imaging tests differ in how they are administered and what they can tell doctors. Here's a rundown.
An X-ray is a two-dimensional photo of the bones taken using electromagnetic radiation. When someone is in the early stages of RA, X-rays may not show irregularities. However, doctors may still find it helpful to use X-rays as a starting point to track the progression of RA over a number of months or years, to see if the condition is getting worse.
An X-ray can measure spacing of the joints, which can help doctors look for narrowing in those areas. X-rays can also help detect erosions (bone damage) and osteopenia, the bone softening that may happen near inflamed joints. X-rays can also show soft tissue structures such as tendons and ligaments. However, X-rays are not as helpful in identifying the inflammation of the joint lining (or synovitis), which is often one of the first symptoms of RA and can damage cartilage and bone permanently. To detect synovitis, rheumatologists tend to prefer ultrasound and MRI.
An ultrasound is a painless procedure that uses sound waves to make images of the body's internal structures. Unlike with an X-ray, no radiation is used in ultrasonography. During the test, a technician moves a device called a transducer over the skin, applying gentle pressure to the area that's being studied.
Ultrasound has been shown to be better than X-Ray at detecting synovitis. Ultrasound may be performed in your doctor’s office, at a hospital, or at an imaging facility. For people who have seronegative RA, meaning blood work does not show the usual antibodies associated with RA, ultrasound has been especially helpful in diagnosis. As one myRAteam member said, "All my blood work comes back normal, but on ultrasound I have tons of joint inflammation."
You may hear the word "Doppler" used with regard to your ultrasound. Doppler technology reflects sound waves off red blood cells, and it can measure blood flow, unlike regular (gray-scale) ultrasound. Some physicians may prefer Doppler imaging, especially for its ability to show blood flow within the joint lining, which can help diagnose synovitis.
Usually an ultrasound is noninvasive, but in some cases, your doctor may order the test to be done with an injectable solution — known as "ultrasound with contrast." This sulphur hexafluoride solution (known as SonoVue) contains tiny bubbles that strengthen the sound waves' reflection during ultrasound. This helps make body parts more visible by creating a higher-contrast image. Some researchers have found that an ultrasound with contrast is a better tool for evaluating issues such as synovitis than a Doppler ultrasound.
Another radiation-free option, MRI is considered the most sensitive imaging test for diagnosing RA — although it is usually not necessary. MRI technology combines radio waves with a magnetic field to produce highly detailed images. As one myRAteam member wrote, "MRIs are much more detailed. I have one on my hands every year to make sure the disease is under control." Another wrote, "My rheumatologist ordered an MRI with contrast of my hands after my blood tests were normal. It showed joint space narrowing and was helpful in guiding treatment."
MRI can be more expensive and time-consuming than other imaging tests, and you'll need to visit either a hospital or an outpatient imaging facility to have it done.
An MRI is especially useful for detecting potential signs of RA, including:
In addition to helping diagnose RA, MRIs can be used to monitor disease progression.
During an MRI, you'll need to lie inside the machine, which is actually a large, tube-shaped magnet. The procedure is noninvasive. You won't feel the magnetic waves, but the space is enclosed and you may hear the magnet's loud, thumping sounds. The MRI technician may offer headphones or earplugs to help muffle the noise. If you have claustrophobia, you may be able to receive a sedative before the test.
You'll need to remove anything that might interfere with the magnet, such as glasses, dentures, hearing aids, underwire bras, and jewelry. Due to the use of the magnetic field, certain people may not be eligible for an MRI. Pregnancy, epilepsy, or the presence of an implanted device (such as a pacemaker or prosthetic) are some situations that would prevent you from getting an MRI.
Like ultrasound, some MRIs are performed with contrast to help create a more detailed picture. In this case, a substance called a gadolinium-based contrast agent (GBCA) is used. The U.S. Food & Drug Administration (FDA) has issued some warnings about GBCAs. It's important to tell your doctor if you are pregnant (or think you might be) or if you have any kidney issues. People with allergies (including to shellfish and iodine), sickle cell disease, asthma, or low blood pressure may also be affected by contrast solutions. You should also let your physician know the date of your last GBCA scan, if you've had one before.
Using contrast may add to the overall time spent at an MRI appointment. As one myRAteam member wrote, "Spent five hours at the rheumatologist today for an MRI with contrast. Long appointment … it was a six-hour round trip."
Looking for support and a place to share your RA-related questions, concerns, and victories? If you join myRAteam, a support group and social network for people with RA, you'll be welcomed into a community with more than 137,000 members. Some are newly diagnosed, while others have been dealing with RA and its challenges for decades. Members often swap stories and tips about their experiences navigating the different types of testing, including imaging.
Has your doctor ordered an X-Ray, ultrasound, or MRI for your RA? Do you have suggestions for others who might be going in for these tests? Share your tips in a comment below or on myRAteam.