title: Automatic atlas-based three-label cartilage segmentation from MR knee images.
abstract: Osteoarthritis (OA) is the most common form of joint disease and often characterized by cartilage changes. Accurate quantitative methods are needed to rapidly screen large image databases to assess changes in cartilage morphology. We therefore propose a new automatic atlas-based cartilage segmentation method for future automatic OA studies. Atlas-based segmentation methods have been demonstrated to be robust and accurate in brain imaging and therefore also hold high promise to allow for reliable and high-quality segmentations of cartilage. Nevertheless, atlas-based methods have not been well explored for cartilage segmentation. A particular challenge is the thinness of cartilage, its relatively small volume in comparison to surrounding tissue and the difficulty to locate cartilage interfaces - for example the interface between femoral and tibial cartilage. This paper focuses on the segmentation of femoral and tibial cartilage, proposing a multi-atlas segmentation strategy with non-local patch-based label fusion which can robustly identify candidate regions of cartilage. This method is combined with a novel three-label segmentation method which guarantees the spatial separation of femoral and tibial cartilage, and ensures spatial regularity while preserving the thin cartilage shape through anisotropic regularization. Our segmentation energy is convex and therefore guarantees globally optimal solutions. We perform an extensive validation of the proposed method on 706 images of the Pfizer Longitudinal Study. Our validation includes comparisons of different atlas segmentation strategies, different local classifiers, and different types of regularizers. To compare to other cartilage segmentation approaches we validate based on the 50 images of the SKI10 dataset.
authors.affiliation: Department of Computer Science, University of North Carolina at Chapel Hill, USA. Electronic address: shan@cs.unc.edu.
authors.forename: Liang
authors.initials: L
authors.lastname: Shan
authors.affiliation: Toshiba Research Europe, 208 Cambridge Science Park, Cambridge CB4 0GZ, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Zach
authors.affiliation: Department of Radiology, Duke University, USA.
authors.forename: Cecil
authors.initials: C
authors.lastname: Charles
authors.affiliation: Department of Computer Science, University of North Carolina at Chapel Hill, USA; Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Niethammer
mesh_terms: D000465:Algorithms; D002358:Cartilage, Articular / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D020370:Osteoarthritis, Knee / Q000473:pathology*
keywords: Atlas; Automatic; Cartilage; Segmentation; Three-label