A modification of the Omeract RA MRI score for erosions for use with an extremity MRI system with reduced field of view

Abstract

Objectives: To develop and test the reliability of a modified version of the OMERACT rheumatoid arthritis magnetic resonance imaging score (RAMRIS) for erosions using extremity MRI (eMRI) with reduced field of view (RAMRIS-RV). Methods: Using a MagneVu 0.2 T machine, the preliminary RAMRIS-RV assessed erosions in metacarpophalangeal (MCP) joints 2-3, bases of metacarpal (MC) 2-5, and all wrist bones excluding base MC 1, pisiform and trapezium. T1 weighted images of >500 MCP and wrist bony sites from a mixed severity RA and control cohort were evaluated. An inter-reader reliability study evaluating 300 wrist and 160 MCP bony sites was then performed. Results: Mean per cent exact (and close) agreement results were as follows: MCP proximal sites 83.5 (96.2), MCP distal 54.4 (77.2), bases MC 2-4 85.2 (96.7), carpal bones 79.0 (92.1), distal radius/ulna 66.4 (87.8). The base of MCP 5 was visualised in (50% cases (13/25) and was removed from the final RAMRIS-RV. Conclusions: The RAMRIS-RV is a practical tool that can be used with eMRI with a reduced field of view. This study shows excellent inter-reader reliability for erosion assessment, albeit in a reduced number of bony sites. M agnetic resonance imaging (MRI) has become increasingly recognised as a validated outcome measure for evaluating rheumatoid arthritis (RA).1 In terms of bone damage evaluation, the tomographic nature of MRI provides a significant improvement in sensitivity for erosion detection, as evidenced by recent studies comparing computed tomography, MRI and conventional radiographs. 2-4Extremity-MRI (eMRI) machines have been developed primarily for use in the outpatient clinic setting. Such machines have modest space requirements with only the extremity of interest needing to be placed inside the machine, enhancing patient acceptance, reducing cost and increasing availability. 5While these provide valuable alternatives to high field machines, there are some significant trade-offs. For example, since most of the machines use a smaller magnet strength, this results in a degree of compromise for image clarity as well as limitations in the field of view (FOV).In order to use MRI as an outcome measure in a reliable and validated form, the MRI Inflammatory Arthritis Task Force of the Outcome Measures in RA Clinical Trials group (OMERACT) has developed the RA MRI score (RAMRIS) which is presented in the EULAR-OMERACT Image Reference Atlas 6 and has been subsequently validated. [7][8][9] However, the application of the RAMRIS to all eMRI machine images may be limited, as it was developed using images that evaluated all the metacarpophalangeal (MCP) joints and/or the entire carpus.The primary objective of this work was to develop a modified version of the RAMRIS scoring system-the RAMRIS-RV (Restricted field of View)-which could be used to score erosions on images produced by eMRI machines with a restricted field of view. The performance of the RAMRIS-RV was then assessed by an inter-reader reliability study and final modifications to the scoring system made....

A comparison of dedicated 1.0T extremity MRI vs large-bore 1.5T MRI for semiquantitative whole organ assessment of osteoarthritis: the MOST study

“…To date comparative studies evaluating performance of semiquantitative assessment of OA on a dedicated intermediate-field MR system when compared to a standard 1.5 T large-bore system have not been performed. Concerns have been raised that the image quality of intermediate-field extremity systems might be compromised due to a restricted field-of-view, lower signal-to-noise ratio and field inhomogeneities when applying frequency-selective fat saturation 23,24. Thus, we wished to compare semiquantitative whole-organ assessment of OA on a 1.0 T extremity system using a 1.5 T large-bore system as the reference standard and to evaluate if agreement of scoring between the two systems is comparable to the usually observed inter- and intra observer reliability exercises performed on 1.5 T systems.…”

Comparison of 1.0-T Extremity MR and 1.5-T Conventional High-Field-Strength MR in Patients with Rheumatoid Arthritis

“…A further limitation of some extremity MR systems has been their restricted field of view, necessitating a modification of the RAMRIS score for use in such systems (24). In our study, a 10-cm field of view was used in both the extremity and conventional systems, allowing imaging of either the second through fifth MCP joints or the whole wrist joint from the distal radioulnar joint to the carpometacarpal joints.…”