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Open Access Research article

Quantitative assessment of synovitis in patients with rheumatoid arthritis using fluorescence optical imaging

Valentin S Schäfer1*, Wolfgang Hartung1, Patrick Hoffstetter2, Jörn Berger3, Christian Stroszczynski4, Martina Müller5, Martin Fleck15 and Boris Ehrenstein1

Author Affiliations

1 Department of Rheumatology and Clinical Immunology, Asklepios Medical Center Bad Abbach, 93077 Bad Abbach, Germany

2 Department of Radiology, Asklepios Medical Center Bad Abbach, Bad Abbach, Germany

3 Mivenion GmbH, Berlin, Germany

4 Department of Radiology, University Medical Center Regensburg, Regensburg, Germany

5 Department of Internal Medicine (I), University Medical Center Regensburg, Regensburg, Germany

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Arthritis Research & Therapy 2013, 15:R124  doi:10.1186/ar4304

Published: 18 September 2013

Abstract

Introduction

To prospectively evaluate quantitative assessment of fluorescence optical imaging (FOI) for differentiation of synovitic from non-synovitic joints in patients suffering from rheumatoid arthritis (RA).

Methods

FOI of the hands was performed in patients with active RA, and a stratified quantitative fluorescence readout (FLRO) of 3 phases (1-120 s; 121-240 s; 241-360 s) was generated for 5 individual joints of the clinical predominant hand (carpal joint, metacarpophalangeal and proximal interphalangeal joints of digits II & III). To dissect the effect of the overall perfusion of the hand from the perfusion due to synovitis, a fluorescence ratio (FLRA) was additionally calculated, dividing each FLRO by the readout of the eponychium of digit II. The mean FLRO and FLRA were compared between joints with absent vs. present synovitis determined by clinical examination, grayscale, color Doppler ultrasonography, or magnetic resonance imaging (MRI).

Results

The analysis for 90 individual joints from 18 patients yielded FLRO ranging from 4.4 to 49.0 × 103, and FLRAs ranging from 0.37 to 2.27. Overall, the analyses based on the FLRA revealed a higher discrimination than the analyses related to the FLRO, demonstrating most significant differences in phases 2 and 3. A sensitivity of 26/39 (67%) and a specificity of 31/40 (77%) were calculated for FLRA of phase 3 using a cut-off value of more than 1.2 to detect MRI-confirmed synovitis with FOI.

Conclusions

FOI has a potential for visualizing synovitis in subjects with RA. For adequate FOI interpretation, quantitative analysis should be based on the novel FLRA calculated for phases 2 and 3.