Combined surface and volume processing for fused joint segmentation

Abstract

Purpose Segmentation of rheumatoid joints fromCTimages is a complicated task. The pathological state of the joint results in a non-uniform density of the bone tissue, with holes and irregularities complicating the segmentation process. For the specific case of the shoulder joint, existing segmentation techniques often fail and lead to poor results. This paper describes a novelmethod for the segmentation of these joints. Methods Given a rough surface model of the shoulder, a loop that encircles the joint is extracted by calculating the minimum curvature of the surface model. The intersection points of this loop with the separate CT-slices are connected by means of a path search algorithm. Inaccurate sections are corrected by iteratively applying a Hough transform to the segmentation result. Results As a qualitative measure we calculated the Dice coefficient and Hausdorff distances of the automatic segmentations and expert manual segmentations of CT-scans of ten severely deteriorated shoulder joints. For the h merus and scapula the median Dice coefficient was 98.9% with an interquartile range (IQR) of 95.8-99.4 and 98.5% (IQR 98.3-99.2%), respectively. The median Hausdorff distances were 3.06mm (IQR 2.30-4.14) and 3.92mm (IQR 1.96 - 5.92mm), respectively. Conclusion The routine satisfies the criterion of our particular application to accurately segment the shoulder joint in under 2min.We conclude that combining surface curvature limited user interaction and iterative refinement via a Hough transform forms a satisfactory approach for the segmentation of severely damaged arthritic shoulder joints. © CARS 2009.