Browsing by Author "Fripp, J"

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    3D shape context surface registration for cortical mapping
    (Institute of Electrical and Electronics Engineers (IEEE), 2010-04-16) Acosta, O; Fripp, J; Rueda, A; Xiao, D; Bonner, E; Bourgeat, P; Salvado, O
    Deformable registration of cortical surfaces facilitates longitudinal and intergroup comparisons of cortical structure and function in the study of many neurodegenerative diseases. Non-rigid cortical matching is a challenging task due to the large variability between individuals and the complexity of the cortex. We present a new framework for computing cortical correspondences on brain surfaces based on 3D Shape Context and mean curvatures of partially flattened surfaces (PFS). Our approach is scale invariant and provides an accurate and anatomically meaningful alignment across the population. Registering PFS, instead of original cortical surfaces, simplifies the determination of shape correspondences, overcoming the problem of intersubject variability, while still guaranteeing the alignment of the main brain lobes and folding patterns. We validated the approach using 30 segmented brains from the OASIS database registered to a common space and compared the results with Freesurfer. In average, mean absolute distance of 0.36 and Hausdorff distance of 5.06 between moving and target surfaces are obtained. Further localization of labelled areas on each hemisphere demonstrated the accuracy of the technique.
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    Hybrid non-rigid registration method for registering rat skeletons from micro-CT images
    (Society of Nuclear Medicine and Molecular Imaging, 2009-05) Xiao, D; Zahra, D; Bourgeat, P; Tamayo, OA; Berghofer, PJ; Fripp, J; Grégoire, MC; Salvado, O
    Objectives: A hybrid non-rigid registration method for automatic rat spine detection and registration and further rat limbs registration was proposed. Methods: We first developed an automatic algorithm to extract the rat spine from its whole-body skeleton and then detect top point on the spinous process of each vertebra starting from the first vertebra at thoracic vertebrae towards the tail. The extracted points were matched to the predefined corresponding points of the spine in a rat atlas. Their correspondences field was used to perform skeletons registration by thin-plate-spline (TPS). Further, we extend 3D shape context algorithm for landmarks matching for rat limbs between the atlas and the newly extracted skeletons. The correspondences found were used to perform the rat limb skeletons registration by TPS. Results: Experiments were described using phantoms and actual rat skeletons. Mean square errors decrease was observed during registration process. Visually, the skeletons were successfully registered. Conclusions: The method can improve the robustness of rat skeleton registration, even in the case of large variation in some postures and this first step work can be extended to further improve rat organs registration guided by the correspondences found from the skeletons.© 2009 by Society of Nuclear Medicine