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The structural basis of MRI bone erosions: an assessment by microCT
  1. Andreas Albrecht1,
  2. Stephanie Finzel1,
  3. Matthias Englbrecht1,
  4. Jürgen Rech1,
  5. Axel Hueber1,
  6. Philipp Schlechtweg2,
  7. Michael Uder2,
  8. Georg Schett1
  1. 1Department of Internal Medicine 3, University of Erlangen-Nuremberg, Erlangen, Germany
  2. 2Institute of Radiology, University of Erlangen-Nuremberg, Erlangen, Germany
  1. Correspondence to Professor Georg Schett, Department of Internal Medicine 3, Rheumatology and Immunology; University of Erlangen-Nuremberg; Krankenhausstrasse 12, Erlangen D-91054, Germany; georg.schett{at}


Objective To determine whether erosions appearing in MRI in patients with rheumatoid arthritis (RA) represent true erosions.

Methods 50 RA patients received 1.5 T MRI and microCT (μCT) of the dominant hand. Erosion counts were assessed in coronal T1 weighted MRI sections and in coronal as well as axial μCT sections of the metacarpophalangeal (MCP) joints II–IV. Extent of erosions was assessed by RA MRI Score (RAMRIS) erosion score (MRI) and by three-dimensional assessment of erosion volume (μCT).

Results 111 of the 600 evaluated joint regions showed erosions in the MRI and 137 in the μCT. In only 28 regions false negative lesions (μCT positive, MRI negative) were found, all of which were very small lesions with a volume of less than 10 mm3. Only two results were false-positive (μCT negative, MRI positive). RAMRIS erosion scores were strongly correlated to erosion volumes in the μCT (Pearson's r=0.514, p<0.001). Mean RAMRIS erosion scores were below 1 with erosion volumes up to 1.5 mm3, below 2 with erosion volumes up to 20 mm3 and over 2 with volumes of more than 20 mm3.

Discussion MRI erosions are generally based on true cortical breaks as shown by μCT. MRI is sensitive to detect bone erosions and only very small lesions escape detection. Moreover, RAMRIS erosion scores are closely linked to the absolute size of bone erosions in the μCT.

  • Rheumatoid Arthritis
  • Magnetic Resonance Imaging
  • Early Rheumatoid Arthritis

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  • Correction
    BMJ Publishing Group Ltd and European League Against Rheumatism