Page 114 - Imaging of Osteoarthritis and Rheumatoid Arthritis in Hand Joints

Chapter 6
unable to participate because of logistical problems. In most of these patients, this was because DMARD or steroid therapy needed to start before they were able to undergo two MRI-scans. Our patient sample will therefore probably have a low number of patients in which clinical findings were very suspect for RA. Another limitation of the study is that 14 patients did not have both ultrasound examinations, usually because one of the sonographers was unavailable on the MRI days, lowering the sample size of the comparison with ultrasound. A known limitation of the Artoscan 0.2 T unit specifically is that its maximum field of view is restricted to 12 cm. For 6 out of 40 patients the length of the complete wrist and MCP joints was larger than 12 cm, and the proximal part of the wrist was therefore not imaged. A total of 4 erosions were detected on the 1.5T MRI in the areas not imaged by the Artoscan. Newer low field scanners generally have a bigger FOV, and therefore may not have this problem.
In conclusion, in patients with arthralgia and early arthritis, low field extremity MRI is good in detecting synovitis, and more sensitive than US. It was less sensitive for detection of erosions than high field MRI. Most BME lesions were missed with low field MRI, suggesting that higher field-strength scanners should be used when one is interested in BME.
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