Comparison of 1.0-T Extremity MR and 1.5-T Conventional High-Field-Strength MR in Patients with Rheumatoid Arthritis

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Abstract
To prospectively determine the comparability of 1.0-T extremity magnetic resonance (MR) imaging and 1.5-T conventional MR for the evaluation of the hand and wrist in assessment of patients with rheumatoid arthritis (RA). Institutional ethics approval and written informed consent were obtained. Thirty-two patients (30 women, two men; mean age, 52 years) with RA twice underwent MR of either the most symptomatic hand (n = 21) or wrist (n = 11), once performed with a 1.0-T extremity MR system and once with a 1.5-T conventional MR system. The MR examinations were independently assessed by two radiologists blinded to imaging platform and patient clinical information for erosions, synovitis, and bone marrow edema (BME), according to the Rheumatoid Arthritis MR Imaging Score (RAMRIS). One radiologist reevaluated all cases a second time to determine the intraobserver variability for each system. Patient comfort was assessed with a questionnaire. Intraclass correlation coefficients (ICCs) and smallest detectable differences (SDDs) were measured. ICCs for intermachine agreement were 0.97-0.99 for erosions, 0.88-0.97 for synovitis, and 0.98-0.99 for BME for both readers. The SDDs between the two systems, expressed as a percentage of the maximum score, ranged from 3.3% to 12.2% for erosions, from 7.4% to 14.8% for synovitis, and from 5% to 9.9% for BME for both readers. ICCs for interreader agreement ranged from 0.69 to 0.99 and for intrareader agreement, from 0.88 to 0.99. There were substantial differences in the subjective patient assessment of confinement, system noise, and difficulty with immobilization, and 95.8% of patients preferred examinations performed with extremity MR. The 1.0-T extremity MR system demonstrates synovial and osseous changes in RA equally as well as a 1.5-T conventional MR system and is preferred by patients.

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