Magnetic resonance imaging (MRI) procedures have opened new windows into examining joints, but questions remain about the added value of these images in routine rheumatology practice. A session at the ACR/ARHP Annual Scientific Meeting in Boston last November focused on how results obtained from peripheral, or extremity, MRI devices should guide early intervention in rheumatoid arthritis (RA) when considering the use of biologics.
“You can’t help but be struck by the accuracy, by the beautiful nature of the pictures we have all come to recognize,” said Arthur Kavanaugh, MD, professor of medicine at the University of California, San Diego School of Medicine in La Jolla, Calif., referring to MRI-produced images.
The most established technique for rheumatologists to visualize joints remains the traditional x-ray, which is still the gold standard for diagnosing and staging RA, said Dr. Kavanaugh, who moderated the session. As the option for using MRI has started to enter the field of rheumatology, most experts agree that the new images show much more detail than x-rays.
Good—but Good Enough?
The question facing rheumatologists is whether this added level of sensitivity moves diagnosis or treatment of RA patients forward enough. Dr. Kavanaugh wondered whether these new details provide insights that could not be found using the existing array of available tools.
One drawback for MRI images, including peripheral and full-body devices, is the lack of an accepted scoring system to assess what is being seen. For x-rays as well as CT scans, there are established and widely used scoring systems to determine the extent of bone erosion and other related RA problems.
Traditional x-rays are often preferred when looking into potentially damaged joints because the procedure is widely available, easy to perform, well tolerated by patients, and relatively inexpensive. Full-body MRI procedures are less available and more expensive, and some patients feel uncomfortable lying in an enclosed space.
Peripheral MRIs offer potential solutions to some of these challenges. The portable nature of the technique means it can be placed on the target joints, which many patients prefer to having to lay in a full MRI machine. The peripheral MRI machines are priced so that individual practices could purchase them, making them potentially widely available.
But experts, including an ACR Extremity MRI Task Force that examined the merits of these portable devices, still have questions.
While the full MRIs produce high magnetic fields, many as high as 3 Teslas, the peripheral versions produce low fields, some as small as 0.2 Teslas.
Michael H. Weisman, MD, director of the division of rheumatology at Cedar Sinai Medical Center in Los Angeles, argued that peripheral MRIs should not be part of common practice in dealing with RA until the devices are proven to be better diagnostic tools. He says that the added expense of peripheral MRI does not yet appear to outweigh the information that can be gathered by traditional x-rays, CT scans, and physical examination methods. He acknowledged that MRIs would allow doctors to see some new details, such as inflammation of the synovium, but biopsies can also reveal such information. Dr. Weisman considered the advantages of the information obtained from a more expensive MRI machine with that from the less expensive approach.
Bone erosion is another area where MRI images seem to be of potential usefulness. Dr. Weisman said that bone erosions appear earlier on MRIs and often in greater numbers than those seen on x-rays. However, he cautioned that these MRI images do not fepict well the boundaries of bone erosion. On x-rays and CT scans, bone appears bright, but it tends to fade in MRI-produced images. There also appears to be no information on whether these MRI devices can distinguish between RA and other diseases found in the joint.
The question facing rheumatologists is whether this added level of sensitivity moves diagnosis or treatment of RA patients forward enough.
Some In Favor of the Technology
Despite the questions, some rheumatologists believe peripheral MRIs should be utilized more widely in common practice. Paul Emery, MA, MD, of Leeds University in England, supports integrating peripheral MRIs into rheumatology practice now. He acknowledges that some questions remain, but that overall, MRI provides detailed images that may be the difference between simply managing an illness and putting a disease into remission.
Cost, when compared with traditional x-rays, should not be a consideration when trying to provide patients with the fastest and most accurate diagnosis of the earliest stages of RA, Dr. Emery said. “The cost of mismanaging a patient is extraordinarily high,” he noted.
A key advantage of MRI is its ability to detect changes in the joint before they become visible on x-rays. Such a head start can be critical for determining which patients would most benefit from biologic treatments. Putting patients on biologics early can make a long-term difference in managing RA, said Dr. Emery.
Britain’s National Health Service has already accepted the benefits of peripheral MRI and allows their use by doctors as a diagnostic tool, Dr. Emery noted.
The portable devices can be used to identify features that can be influenced by early tumor necrosis factor (TNF) blockade. There is evidence that patients who start early on anti-TNF treatments can achieve remission compared with patients treated with disease-modifying antirheumatic drugs.
“It’s crucial to start early to get patients into remission,” Dr. Emery said.
An advantage of MRI over traditional x-ray is that there are fewer chances to miss bone erosion in MRI images. A slight hand turn on two-dimensional x-rays can hide bone erosion, said Dr. Emery. He admitted that there are issues with false positives based on examining MRI images, but he suggested this is more of a training issue than a functional problem.
When, and if, peripheral MRIs come into mainstream use among rheumatologists, there is also the issue of who should read the images. Some in the radiology community have argued they should take on the task of examining MRI images, but other experts contend that rheumatologists should be able to read their own MRI images.
The peripheral MRI debate may just be beginning. As more studies on the subject emerge, experts may revisit the discussion. For now, many experts are taking a wait and see approach, leaning to the idea the peripheral MRIs may not yet be ready for widespread use.
Greg Lavine is a freelance journalist based in Maryland.
