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AbstractRecent technological innovations have had a large impact in the field of medicine, and it would be desirable, for example, in cardiology, neurology and orthopaedics, to simulate treatment using a numerical model personalized for the individual patient before proceeding to actual treatment. Moreover, as the choice of medical treatment often depends more on the rate of progression than on the severity of an anomaly at any particular instant, there is a need for simulation tools that permit observation of the evolution of morphological or functional anomalies. The purpose of the work described here is to study a simulation tool that would permit the clinician to document progression of skeletal deformation in adolescents afflicted with scoliosis, to choose the most appropriate treatment. More particularly, the objective is to provide the mathematical formulation of a model for the deformation of the collection of structures forming the human trunk, so that, as a first step, one could monitor the progression of the deformity while using fewer X-rays. The models are based on thin-plate splines, and have undergone preliminary evaluation using data for real scoliotic patients. The results obtained show that the proposed model should adequately approximate the progression of scoliotic deformities, given observations on the external trunk.

This paper presents an extension of a previously-described framework for the specification and manipulation of models of systems. The original framework and its extension include a convenient application programming interface (API), and this paper describes examples of the use of this API in the context of graphical simulation. These examples include the simulation of objects whose definition involves torques, and a brief description of the simulation of air and smoke by means of a model involving particles moving in fluid. [Copyright &y& Elsevier]

In this paper we generalize the method of sweeping, which may be used for both object representation and object visualization, to objects in E4. The generalized sweeping method involves a trajectory in E4, and a three-dimensional cross-section orthogonal to the trajectory. Three alternatives are considered for specifying the relationship between the trajectory and the cross-section, namely the Frenet frame, modified Frenet frames, and the standard viewing-reference coordinate (VRC) frame, where each of these is generalized to the case of four dimensions. We have implemented the method using the four-dimensional VRC frame, and the method is illustrated here by means of two examples involving visualization of objects embedded in E4.