title: Automatic Segmentation of Wrist Bones in CT Using a Statistical Wrist Shape + Pose Model.
abstract: Segmentation of the wrist bones in CT images has been frequently used in different clinical applications including arthritis evaluation, bone age assessment and image-guided interventions. The major challenges include non-uniformity and spongy textures of the bone tissue as well as narrow inter-bone spaces. In this work, we propose an automatic wrist bone segmentation technique for CT images based on a statistical model that captures the shape and pose variations of the wrist joint across 60 example wrists at nine different wrist positions. To establish the correspondences across the training shapes at neutral positions, the wrist bone surfaces are jointly aligned using a group-wise registration framework based on a Gaussian Mixture Model. Principal component analysis is then used to determine the major modes of shape variations. The variations in poses not only across the population but also across different wrist positions are incorporated in two pose models. An intra-subject pose model is developed by utilizing the similarity transforms at all wrist positions across the population. Further, an inter-subject pose model is used to model the pose variations across different wrist positions. For segmentation of the wrist bones in CT images, the developed model is registered to the edge point cloud extracted from the CT volume through an expectation maximization based probabilistic approach. Residual registration errors are corrected by application of a non-rigid registration technique. We validate the proposed segmentation method by registering the wrist model to a total of 66 unseen CT volumes of average voxel size of 0.38 mm. We report a mean surface distance error of 0.33 mm and a mean Jaccard index of 0.86.
authors.forename: Emran Mohammad Abu
authors.initials: EM
authors.lastname: Anas
authors.forename: Abtin
authors.initials: A
authors.lastname: Rasoulian
authors.forename: Alexander
authors.initials: A
authors.lastname: Seitel
authors.forename: Kathryn
authors.initials: K
authors.lastname: Darras
authors.forename: David
authors.initials: D
authors.lastname: Wilson
authors.forename: Paul St
authors.initials: PS
authors.lastname: John
authors.forename: David
authors.initials: D
authors.lastname: Pichora
authors.forename: Parvin
authors.initials: P
authors.lastname: Mousavi
authors.forename: Robert
authors.initials: R
authors.lastname: Rohling
authors.forename: Purang
authors.initials: P
authors.lastname: Abolmaesumi
mesh_terms: D002348:Carpal Bones; D006801:Humans; D025341:Principal Component Analysis; D014057:Tomography, X-Ray Computed; D014953:Wrist; D014955:Wrist Joint