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Optimised, low cost, low field dedicated extremity MRI is highly specific and sensitive for synovitis and bone erosions in rheumatoid arthritis wrist and finger joints: comparison with conventional high field MRI and radiography
  1. B J Ejbjerg,
  2. E Narvestad,
  3. S Jacobsen,
  4. H S Thomsen,
  5. M Østergaard
  1. Departments of Rheumatology and Department of Radiology, Copenhagen University Hospitals at Hvidovre, Rigshospitalet and Herlev, Copenhagen, Denmark
  1. Correspondence to:
    Dr B J Ejbjerg
    Department of Rheumatology, Copenhagen University Hospital at Hvidovre, Kettegaard Allé 30, 2650 Hvidovre, Denmark;


Objective: To evaluate a low field dedicated extremity MRI unit for detection of bone erosions, synovitis, and bone marrow oedema in wrist and metacarpophalangeal (MCP) joints, with a high field MRI unit as the standard reference.

Methods: In 37 patients with RA and 28 healthy controls MRI of the wrist and 2nd–5th MCP joints was performed on a low field MRI unit (0.2 T Esaote Artoscan) and a high field MRI unit (1.0 T Siemens Impact) on 2 subsequent days. MRI was performed and evaluated according to OMERACT recommendations. Additionally, conventional x ray, clinical, and biochemical examinations were performed. In an initial low field MRI “sequence selection phase”, based on a subset of 10 patients and 10 controls, sequences for comparison with high field MRI were selected.

Results: With high field, spin echo MRI considered as the reference method, the sensitivity, specificity, and accuracy of low field 3D gradient echo MRI for erosions were 94%, 93%, 94%, while the corresponding values for x ray examination were 33%, 98%, and 83%. Sensitivity, specificity, and accuracy of low field MRI for synovitis were 90%, 96%, and 94%, and for bone marrow oedema 39%, 99%, and 95%. Intraclass correlation coefficients between low field and high field scores were 0.936 (p<0.005) for bone erosions and 0.923 (p<0.05) for synovitis.

Conclusion: Low field MRI provides high accuracy for detection and grading of erosions and synovitis, with high field MRI as the standard reference. For bone marrow oedema, specificity is high, but sensitivity only moderate. Low cost, patient compliant, low field dedicated extremity MRI provides similar information on bone erosions and synovitis as expensive high field MRI units.

  • FOV, field of view
  • FS, fat saturated
  • GE, gradient echo
  • ICC, intraclass correlation coefficient
  • MCP, metacarpophalangeal
  • MRI, magnetic resonance imaging
  • RA, rheumatoid arthritis
  • SE, spin echo
  • STIR, short τ inversion recovery
  • TE, echo time
  • TR, repetition time
  • high field magnetic resonance imaging
  • low field magnetic resonance imaging
  • rheumatoid arthritis

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  • Published Online First 13 January 2005