Morphological Atlases of Knee Cartilage: Shape Indices to Analyze Cartilage Degradation in Osteoarthritic and Non-Osteoarthritic Population

3D Magnetic resonance imaging of the articular cartilage allows accurate morphological assessment of the cartilage with relevance for identifying osteoarthritis (OA) status and to monitor progression and response to treatment. We propose the creation of morphological atlases of the cartilage using normal subjects segregated by age, sex, and gender. These atlases capture the variation of shape in normal subjects and are then used to classify new imaging studies as belonging to 'normal (asymptomatic of OA)' or 'abnormal (symptomatic of OA)'. The classification is performed by (i) analysis of the 3D deformation field required to move voxels to their corresponding locations in the atlas. Deformations beyond plusmn2SD of normal variations constitute regions with large morphological changes; (ii) generating active shape models from the normal subject data and using the shape coefficients to classify cartilage morphology. The methodology is evaluated with an atlas of 20 normal subjects in one sub-type and testing the classification potential with 3 subjects symptomatic and 3 subjects asymptomatic of OA.