Semi-automated ICRS scoring of equine articular cartilage lesions in optical coherence tomography images

Abstract

BACKGROUND: Arthroscopic optical coherence tomography (OCT) is a promising tool for detailed evaluation of articular cartilage injuries. However, OCT-based articular cartilage scoring still relies on the operator's visual estimation. OBJECTIVES: To test the hypothesis that semi-automated ICRS (International Cartilage Repair Society) scoring of chondral lesions seen in OCT images could enhance intra- and inter-observer agreement of the scoring and its accuracy. STUDY DESIGN: Validation study, using equine cadaver tissue. METHODS: Osteochondral samples (n = 99) were prepared from eighteen equine metacarpophalangeal joints and imaged using OCT. Custom-made software was developed for semi-automated ICRS scoring of cartilage lesions on OCT images. Scoring was performed visually and semi-automatically by five observers, and inter- and intra-observer agreements were calculated. Subsequently, OCT-based scores were compared with ICRS scores based on light microscopy images of the histological sections of matching locations (n = 82). RESULTS: When semi-automated scoring of the OCT images was performed by multiple observers, higher mean intra-observer (83% vs. 77%) and inter-observer (74% vs. 33%) agreement percentages were achieved compared with visual OCT scoring. Histology-based scores from matching regions of interest agreed better with visual OCT-based scoring than with semi-automated OCT scoring, however, accuracy of the software was improved by optimising the threshold combinations used to determine the ICRS score. Main limitations Images were obtained from cadavers. CONCLUSION: Semi-automated scoring software improved reproducibility of ICRS scoring of chondral lesions in OCT images and made scoring less dependent on the observer. The image analysis and segmentation techniques adopted in this study warrant further optimisation to achieve better accuracy with semi-automated ICRS scoring and studies on in vivo application are required. This article is protected by copyright. All rights reserved.