SCIENTIFIC ARTICLE Dynamic contrast-enhanced imaging of the wrist in rheumatoid arthritis: dedicated low-field (0.25-T) versus high-field (3.0-T) MRI Ryan K. L. Lee & James F. Griffith & D. F. Wang & L. Shi & David K. W. Yeung & Edmund K. Li & L. S. Tam Received: 21 November 2014 /Revised: 22 January 2015 /Accepted: 12 February 2015 # ISS 2015 Abstract Objective To compare the assessment of wrist synovitis sever- ity, synovial volume and synovial perfusion parameters on a dedicated low-field (0.25-T) to that of a high-field (3-T) whole-body MR system in patients with rheumatoid arthritis (RA). Methods Twenty-one patients (mean age 50.0±9.8 years) with active RA were recruited prospectively. Dynamic contrast-enhanced MRI examination of the most severely af- fected wrist was performed at both 0.25 T and 3 T. Three MRI- derived parameters, synovitis severity (RAMRIS grade), sy- novial volume (ml 3 ) and synovial perfusion indices (maxi- mum enhancement and enhancement slope), were compared. Results Comparing 0.25- and 3-T MRI, there was excellent agreement for semiquantitative assessment (r: 0.80, p <0.00001) of synovitis (RAMRIS) as well as quantitative assessment (r: 0.94, p <0.00001) of synovial volume. Good agreement for synovial Emax (r: 0.6, p =0.002) and fair agree- ment (r: 0.5, p =0.02) for synovial Eslope was found. Conclusions Imaging of the RA wrist at 0.25 T yields excel- lent correlation with 3 T with regard to the synovitis activity score (RAMRIS) and synovial volume measurement. Fair to good correlation between low- (0.25-T) and high-field (3-T) MR systems was found for perfusion parameters, being better for Emax than for Eslope. Keywords Wrist perfusion . Dynamic . MRI . Low field . High field . Dedicated MRI Introduction When determining the need for and response to treatment in rheumatoid arthritis (RA) and other inflammatory arthropa- thies, the degree of inflammatory activity is more clinically relevant than the degree of pre-existing joint damage [1]. Such assessment of inflammatory activity needs to be quantifiable, reliable and readily repeatable. Therefore, a robust, accurate and easy-to-perform assessment method is required. Currently, the volume of synovial proliferation and activity of this synovial proliferation (as determined by tissue perfu- sion) are the two most useful imaging markers of synovial inflammation. These can be evaluated by color Doppler ultra- sound, contrast-enhanced ultrasound or contrast-enhanced MRI. Postcontrast static MRI is used to determine the amount of synovial proliferation, while dynamic contrast-enhanced (DCE) MRI provides a reliable quan- tification of tissue perfusion [2]. High-field MRI systems generate images of higher spatial, contrast and temporal resolution, although this improved ca- pability may not necessarily translate into higher diagnostic power when, for example, assessing disease activity in RA [3]. The possibility of comparable diagnostic data being ac- quired from low-field, dedicated MRI systems further extends the applicability of these systems [4]. Low-field MRI is com- monly used in inflammatory arthropathy to help with early diagnosis and assess synovial proliferation and static enhance- ment [2]. The aim of this study was to compare low- (0.25-T) R. K. L. Lee : J. F. Griffith (*) : D. F. Wang : D. K. W. Yeung Department of Imaging and Interventional Radiology, Prince Of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, SAR, China e-mail: griffith@cuhk.edu.hk L. Shi Department of Medicine and Therapeutics, Division of Neurology, The Chinese University of Hong Kong, Hong Kong, SAR, China E. K. Li : L. S. Tam Department of Medicine, Division of Rheumatology, Prince Of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, SAR, China Skeletal Radiol DOI 10.1007/s00256-015-2120-x