• Simon Krabbe, Iris Eshed, Susanne Juhl Pedersen, Pernille Bøyesen, Jakob M Møller, Flemming Therkildsen, Mette Bjørndal Axelsen, Ole Rintek Madsen, and Mikkel Østergaard.
• Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Copenhagen University Hospital Glostrup, Copenhagen, Denmark, Department of Radiology, Sheba Medical Center, Tel Hashomer, Israel, Department of Rheumatology, Diakonhjemmet Hospital, Oslo, Norway, Department of Radiology, Copenhagen University Hospital Herlev, Metropolitan University College Copenhagen and Department of Rheumatology, Copenhagen University Hospital Gentofte, Copenhagen, Denmark. simonkrabbe@gmail.com.
• Rheumatology (Oxford). 2014 Aug 1; 53 (8): 1446-51.

ObjectiveThe aim of this study was to examine the influence of different MRI unit field strengths, coil types and image resolutions on the OMERACT RA MRI scoring system (RAMRIS) of bone marrow oedema (BME) and image quality.MethodsForty-one patients and 12 healthy controls participated in this cross-sectional study. Coronal short tau inversion recovery (STIR) and T1-weighted sequences were obtained at 0.23, 0.6, 1.5 and 3T using flex coils (Flex). Additional STIR sequences were obtained with phased array extremity coils (Extr) (at 0.6 and 1.5T) and higher resolution (at 1.5T). In otal, 338 STIR image sets were anonymized and scored according to RAMRIS and parameters of image quality were measured.ResultsThe BME sum scores were similar overall when comparing the different MRI units, coil types and voxel sizes, yet significantly higher at the higher resolution of 1.5T Extr compared with 0.23T Flex (P = 0.004), 0.6T Flex (P = 0.03), 1.5T Flex (P = 0.05) and 3T Flex (P = 0.001). Mean differences were relatively minor (0-3.5). Intrareader reliability of BME scores was high [intraclass correlation coefficient ≥ 0.90 for all except 0.23T (0.81) and percentage exact agreement 81-88%]. The smallest detectable difference was better at 0.6, 1.5 and 3T (9-29% of maximum value) than at 0.23T (40%). Image quality was lowest at 0.23T.ConclusionNo major, consistent differences were found between BME scores using STIR sequences obtained at different field strengths, coil types and image resolutions, suggesting that these are equally suited for assessment of BME in RA. However, parameters of image quality and intrareader reliability (favouring 0.6, 1.5 and 3T) should be considered when selecting the MRI acquisition strategy.© The Author 2014. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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