SAT0552 IMAGING OF CORTICAL INTERRUPTION IN THE METACARPOPHALANGEAL JOINTS WITH HIGH-RESOLUTION PERIPHERAL QUANTITATIVE COMPUTED TOMOGRAPHY SHOWS HIGH RELIABILITY AND ACCEPTABILITY FOR PATIENTS WITH RHEUMATOID ARTHRITIS.
Authors: R. Klose-Jensen, K. K. Keller, B. Langdahl, E. M. Hauge
Journal: Annals of the Rheumatic Diseases (2020)

Background: High-Resolution peripheral Quantitative Computed Tomography (HR-pQCT) has been proposed as a modality for assessment of disease severity in inflammatory arthritis. The excellent resolution (82µm 3 ) and the inherent contrast between bone and soft tissue makes it a gold standard reference for the detection of bone damage in vivo. However, the nine minutes acquisition time for the metacarpophalangeal (MCP) joints might yield some disadvantages. Having the hand and arm immobilised for this long might discomfort the patients, thereby reducing acceptability, resulting in poor adherence. The longer imaging time might also increase the risk of motion-induced image degradation. Objectives: The objective of this study was two-fold. Firstly, we investigated motion-induced image degradation of 2nd and 3rd MCP joints for two methods of standardised positioning of the hand. Secondly, the acceptability of HR-pQCT imaging was explored for patients with established Rheumatoid Arthritis (RA). Methods: Fifty patients with RA had their 2nd and 3rd MCP joints imaged by HR-pQCT. The patients were scanned two times, using a custom-made positioning splint, with and without an inflatable immobilisation device. In order to investigate acceptability, the patients were afterwards given a questionnaire regarding their procedure experience of HR-pQCT imaging with and without the inflatable hand immobilisation device. For each acquisition, the image quality was graded, and the number, width, depth and length of cortical interruptions were measured. Twenty percent of the acquisitions were reevaluated to determined intrareader reliability using the intraclass correlation coefficient (ICC). Results: The acceptability regarding HR-pQCT imaging was high, with only 6% preferring conventional X-ray compared to 40% of the patients preferring HR-pQCT imaging. The remaining 54% were indifferent to the modality. Seventy-four percent found it hard to keep their fingers at rest during the imaging. Fifty percent of the patients thought the inflatable hand immobilisation device helped keep their fingers at rest compared to only 6% who believed it impaired their ability to keep their fingers at rest. This was not observable in the image quality, however, as the overall image quality was high and no clinically relevant difference of the visual grading between the acquisitions with and without the inflatable hand immobilisation device was observed. The number, width, depth and length of cortical interruption all indicated excellent reproducibility as shown in table 1. No discernible difference between the two acquisitions was observed. Table 1. Intraclass correlation coefficients for the number, width, depth and length of cortical interruptions, with and without the inflatable hand immobilization device. Acquisition 1 Acquisition 2 Cortical interruptions number 0.99 (0.94 to 1.00) 0.98 (0.91 to 1.00) Average cortical interruption width 0.98 (0.92 to 0.99) 0.99 (0.95 to 1.00) Average cortical interruption depth 0.98 (0.92 to 0.99) 0.97 (0.89 to 0.99) Average cortical interruption length 0.93 (0.75 to 0.98) 0.98 (0.94 to 1.00) Acquisition 1 - Without the inflatable hand immobilization device. Acquisition 2 - With the inflatable hand immobilization device. Data presented as mean (95% confidence intervals). Conclusion: The high acceptability signifies the feasibility of the novel HR-pQCT imaging; this was evident by the fact that more patients preferred HR-pQCT imaging compared to conventional X-ray examination. The inflatable hand immobilisation device did not reduce motion-induced image degradation as the overall image quality was high for imaging of the MCP joints in both acquisitions. Our result, however, shows that the patients are more than capable of keeping their fingers at rest for the long acquisition time. Disclosure of Interests: Rasmus Klose-Jensen: None declared, Kresten Krarup Keller: None declared, Bente Langdahl Grant/research support from: Amgen, NovoNordisk, Consultant of: Amgen Inc., Eli Lilly, UCB Pharma, Ellen Margrethe Hauge: None declared