Page 105 - Imaging of Osteoarthritis and Rheumatoid Arthritis in Hand Joints
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 Accuracy of low field MRI in early arthritis
Each patient was also invited for two ultrasound examinations of the same hand imaged with MRI at the same day as one of the MRI examinations. One ultrasound examination (“standardized US”) was performed by a trained researcher (DFTC) using a previously described standardized scanning protocol with fixed probe positions for evaluation in specific imaging planes, 26 based on EULAR guidelines and advice from OMERACT US working group concerning patient and probe positions.27, 28 The second ultrasound examinations (“clinical US”) were performed by an experienced musculoskeletal radiologist (GSRM) using the same standardized scoring form, but without restrictions for probe positions. Both examiners scanned the MCP joints, intercarpal joint area, radiocarpal joint and DRU-joint with grayscale and power Doppler for synovitis and erosions were only assessed in the MCP joints. Both examiners used the following definitions: Synovitis was defined as synovial thickening with bulging above the periarticular bones and/or visible Doppler flow within the synovium. Erosions were defined as a cortex defect, visible in two planes.
Statistical analysis
No formal sample size calculation was performed as we did not know the
frequency of pathology that would be present in patients with inflammatory
hand complaints on MRI. Based on the patient-flow in the REACH we expected 6 that half of our 40 consecutive patients would have clinically observable
arthritis allowing for a sufficient amount of pathology to detect with MRI.
Simple descriptive techniques and calculation of agreement using Kohen’s
Kappa were used to compare the imaging methods.
Out of 150 consecutive patients of the REACH cohort, 104 fulfilled our inclusion criteria, and were invited to participate (Figure 1). Forty-four patients entered the study. Two of those patients could not be scanned with the extremity MRI due to technical problems with the machine, two other patients did not want to complete the study after having the first MRI. Forty patients were analysed with MRI, of which 26 patients also had two ultrasound examinations. 2 patients did

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