Imaging Tests for Rheumatoid Arthritis
When you have rheumatoid arthritis (RA), be prepared for having lots of pictures taken. Luckily, you won’t have to dress up or try to smile naturally. Imaging tests used for the diagnosis or management of RA are only concerned with what’s on the inside of your body.
There are a number of different imaging tests that you may experience in your journey with RA.
X-rays have been the go-to test in rheumatology for a long time. They are a form of electromagnetic radiation that can pass through the body and be recorded as an image, either digitally or on a special film. The end result is an image that shows structures and tissue inside the body.
X-rays show the damage that RA inflammation has created in your joints. They have been used to track the progress of the disease or showing that treatment has halted further damage. However, X-rays are not very sensitive, as they don’t show soft tissue inflammation or very low levels of damage. Therefore, early RA may not show up at all on X-rays, which can delay diagnosis. As well, the lack of sensitivity can make it difficult to assess whether your treatment is working when following the treat to target treatment approach.
When you have X-rays, you will be placed on a metal table or in front of a metal plate, depending on which joint is being X-rayed. You’ll wear a lead apron to protect your reproductive organs from the low-level radiation. The technician will step behind a wall, push a button, and you’ll hear a clunk. That means the X-ray has been taken.
CT stands for computerized tomography. In this type of imaging, the scanner takes a number of X-ray images from different angles, which are then put together by a computer to show cross-sectional images or “slices” of the inside of your body. A CT scan provides more detailed information of the soft tissue, blood vessels, and bones than a regular X-ray.
A CT scanner may look like a donut or a box with a hole. You will be placed on an examination table, which will move through the hole in the donut or the box. When this happens, the ring that comprises the hole will move, taking pictures from different angles. During the scan, the technician will be in a separate room, but close enough that you can speak to them, either directly or through a microphone.
A CT scan will expose you to more radiation than a regular X-ray and many doctors are therefore cautious about using this type of imaging (for more on risks and radiation, see below). However, there are times where the benefits of a CT scan outweigh the risk.
Magnetic resonance imaging or MRI uses a combination of a very powerful magnetic field, radiofrequency pulses, and a computer to provide high-quality images of most anything within your body. It does not use radiation.
This type of imaging is very sensitive to inflammation bone and soft tissue. It is so sensitive, in fact, that it can detect RA damage six months before it shows up on an X-ray. To assess possible changes early on in RA, contrasts for an MRI may be used.
When you get an MRI, you will lie on an exam table that will glide into a very large cylinder. The MRI is accompanied by loud banging noises as rapid pulses of electricity move through the machine. These are not harmful to you. While the test is being done, the technician will be in an adjacent room and you’ll be able to talk to them through a microphone. If you’re claustrophobic, talk to your doctor about anti-anxiety medication.
The MRI is a very powerful magnet. If you have certain metal implants in your body, such as pacemakers, an aneurysm clip, or other metal implants, you should not have an MRI. Joint replacements are usually safe, though. Just in case, be sure to discuss the issue with both your doctor and the MRI technician.
Ultrasound, or ultrasonography, is a fairly new addition to the imaging toolkit in rheumatology. You’re probably familiar with ultrasound as it’s used in other medical tests, such as checking on a developing fetus. Ultrasound for RA is very similar. Gel will be applied to the area under examination and the technician will glide an ultrasound probe over your skin. This should not hurt, unless your joint is very painful.
Ultrasound is very sensitive to detecting both the bone erosion that happens in RA damage, as well as the presence of inflammation. In fact, one study comparing ultrasound to X-rays showed that it detected 127 erosions over the 32 seen on an X-ray. Ultrasound is also quick, does not use radiation, and is fairly inexpensive.
Because ultrasound is a newer tool in rheumatology, it may be difficult to find medical professionals who are trained to use it in this field. However, the American College of Rheumatology is offering a course in Ultrasound Accreditation, so hopefully the tests will become a bigger part of rheumatology practice.
As mentioned above, both X-rays and a CT scans use radiation to create images. As the radiation passes through you, some of it will be absorbed by your body. If you remember that radiation can cause cancer, you might be feeling a bit anxious.
It’s important to keep in mind that being part of our modern society also exposes us to radiation. This background radiation comes from the equipment we use every day, as well as naturally occurring radiation, for instance, cosmic rays. An X-ray of an extremity (arm or leg) exposes you to the equivalent of three hours of simply existing in the world. A CT scan of your head would expose you to the equivalent of eight months of background radiation.
One important note is that if you’re pregnant or think you may be pregnant, make sure to mention this to your doctor and the technician. Radiation can damage a developing fetus. If you are pregnant, your doctor may wish to find an alternate way of assessing your joints.
What’s your experience with imaging? Have you ever received an ultrasound to assess your RA?
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Lene writes the award-winning blog The Seated View. She’s the author of Your Life with Rheumatoid Arthritis: Tools for Managing Treatment, Side Effects and Pain and 7 Facets: A Meditation on Pain.