Magnetic resonance imaging of rheumatoid arthritis: The evolution of clinical applications through clinical trials*
Section snippets
How MRI works
MRI creates images by causing hydrogen nuclei (protons) within tissues to align with the strong magnetic field within the bore of an MRI magnet, much like a compass needle aligns with the magnetic field of the earth 5, 8, 9. Exposing these protons to an additional alternating or rotating magnetic field perpendicular to the static main magnetic field and tuned to the resonant frequency of the protons (ie, applying a radio-frequency pulse) causes the protons to realign with this new field.
Fundamental advantages of MRI
MRI offers 3 principal advantages over conventional radiography for evaluating diarthroidial joints: 1) multiplanar tomography, 2) unparalleled soft tissue contrast, and 3) digital image format.
Specialized MRI systems
A number of new MRI systems have recently been developed that differ radically from the traditional whole-body design of conventional MRI and that offer intriguing alternatives for imaging patients with arthritis (13). These systems come in various sizes and field strengths (Fig 9) and offer a variety of potential advantages over conventional MRI, including significantly lower cost (potentially less than one quarter that of conventional MRI); greater patient comfort and safety, including fewer
MRI evaluation of bone erosion in arthritis
The ability of MRI to evaluate bone has been the subject of considerable debate and misconception. Because of the relative lack of constituent hydrogen protons in cortical and trabecular bone, these structures generally offer no detectable signal on conventional MRI images. On the surface, this may appear as a fundamental limitation of the technique for imaging this tissue. In reality, however, it is the very basis for image contrast, because the linear signal voids of cortical and trabecular
MRI evaluation of synovial changes in arthritis
Before bone erosion in rheumatoid arthritis there is thickening and inflammation of the synovium and accumulation of joint effusion. The goal of modern therapy is to prevent bone erosion from ever developing by suppressing inflammation and synovitis early in the disease process. As with cartilage loss, radiography cannot show these inflammatory and synovial changes directly. MRI, however, is well suited to this. Normal synovium is generally too thin to visualize with conventional MRI. Moreover,
MRI evaluation of articular cartilage
The high water content (proton density) of articular cartilage forms the basis for its signal on MRI. Water content in this tissue depends on the delicate balance between the swelling pressure of the aggregated proteoglycans and the counterresistance provided by the fibrous collagen matrix, but in general terms, changes in cartilage proton density tend to be relatively small (typically less than 20%). Because the water constitutes approximately 70% of the weight of normal articular cartilage,
Imaging complications of arthritis and its treatment
In addition to monitoring changes in the bones, cartilage, and synovium of arthritic joints, MRI is the technique of choice for evaluating many of the complications that may arise because of the disease or the therapy used to treat it. One serious complication is tendon rupture. This may result from mechanical fraying of tendons passing over jagged osteophytes and sharp-edged erosions or from direct tenosynovial invasion of the tendon 74, 75. Tendon avulsion at sites of enthesitis may also
Conclusion
Powerful tools for evaluating the integrity of articular cartilage are emerging from clinical trials designed to test the efficacy and safety of new therapies for rheumatoid arthritis. These clinical trials represent a provocative environment in which imaging techniques originally developed to answer questions about cruciate ligament and meniscal integrity are being forged into new markers designed to serve therapeutic applications in rheumatoid arthritis that are just entering clinical
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Utility of in-office extremity magnetic resonance imaging in rheumatology
2015, Indian Journal of RheumatologyCitation Excerpt :Osteitis can be found surrounding erosions, and this makes it difficult to differentiate the two.65 It is prudent to compare osteitis in T1W sequences (with echo time of <15 ms), where it appears as a low-signal intensity with a ‘feathery’ appearance, and T2W fat saturation and STIR sequences, which give a high signal with ill-defined margins.2 Tenosynovitis can overlap areas of synovitis, as both have an increased signal on T1W post-contrast and T2W fat saturation images, and seen together in axial sections of the wrist.
Proceedings from the 5th Annual International Society for Musculoskeletal Imaging in Rheumatology Annual Conference
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2008, Best Practice and Research: Clinical RheumatologyCitation Excerpt :The availability of new classes of drugs with rapid onset of action and high efficacy is the ideal setting to study sensitivity of the new imaging techniques. As the new drugs are becoming a recognized standard of treatment, the new imaging techniques could also become more common.38 The new techniques are far from being standardized, but studies on this topic are improving steadily.
Improved wrist pannus volume measurement from contrast-enhanced MRI in rheumatoid arthritis using shuffle transform
2007, Magnetic Resonance ImagingCitation Excerpt :A delay of 10 min is usually sufficient to achieve equilibrium in the wrist and hand. Furthermore, a comparison of pre- and postaspiration fluid from knee joints [13,14] indicated that the interpretation of the effusion-synovium borderline is not the major source of variation when the MR images are obtained within 10–15 min after Gd-DTPA injection. Studies have suggested that VEP measured by MRI has predictive value with respect to treatment outcome in RA.
Medical imaging in pharmaceutical clinical trials: What radiologists should know
2005, Clinical RadiologyCitation Excerpt :Imaging can help to detect early disease and define stratified study groups. Many diseases have a “therapeutic window” in their course, during which medical intervention may have a more significant impact.7 In clinical trials, excluding patients who are not likely to progress can substantially increase the statistical power of a study and thereby reduce the number of patients and study duration needed to prove therapeutic efficacy.
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Address correspondence to Charles G. Peterfy, MD, PhD, Chief Medical Officer, Synarc Inc, 455 Market St, Suite 1850, San Francisco, CA 94105. E-mail: [email protected]