— Automatic detection of a falling person in video sequences is an important part of future pervasive home monitoring systems. We propose here a robust method to achieve this goal. Motion is modeled by a Hierarchical Hidden Markov Model (HHMM) whose first layer states are related to the orientation of the tracked person. Finding a consistent way for… (More)
PURPOSE Conformal radiotherapy requires accurate patient positioning with reference to the initial three-dimensional (3D) CT image. Patient setup is controlled by comparison with portal images acquired immediately before patient treatment. Several automatic methods have been proposed, generally based on segmentation procedures. However, portal images are of… (More)
In this article, we present a discrete definition of the classical visibility in computational geometry based on digital straight lines. We present efficient algorithms to compute the set of pixels in a non-convex domain that are visible from a source pixel. Based on these definitions, we define discrete geodesic paths in discrete domain with obstacles.… (More)
PURPOSE We propose to simulate an artificial four-dimensional (4-D) CT image of the thorax during breathing. It is performed by deformable registration of two CT scans acquired at inhale and exhale breath-hold. MATERIALS AND METHODS Breath-hold images were acquired with the ABC (Active Breathing Coordinator) system. Dense deformable registrations were… (More)
The European IST DataGrid project was a pioneer in identifying the medical imaging field as an application domain that can benefit from grid technologies. This paper describes how and for which purposes medical imaging applications can be grid-enabled. Applications that have been deployed on the DataGrid testbed and middleware are described. They relate to… (More)
In this paper, we make an overview of the existing algorithms concerning the discrete curvature estimation. We extend the Worring and Smeulders [WS93] classification to new algorithms and we present a new and purely discrete algorithm based on discrete osculating circle estimation.
—Automatic detection of a falling person in video sequences has interesting applications in video-surveillance and is an important part of future pervasive home monitoring systems. In this paper, we propose a multiview approach to achieve this goal, where motion is modeled using a layered hidden Markov model (LHMM). The posture classification is performed… (More)
keywords: Real-time multiple people tracking On-line articulated appearance learning People identification Body part labeling from silhouette Spectral graph matching Topological model a b s t r a c t Tracking an unspecified number of people in real-time is one of the most challenging tasks in computer vision. In this paper, we propose an original method to… (More)