RESUMO
In this work a tissue aspiration method for the in vivo determination of biological soft tissue material parameters is presented. An explicit axisymmetric finite element simulation of the aspiration experiment is used together with a Levenberg-Marquardt algorithm to estimate the material model parameters in an inverse parameter determination process. An optimal fit of the simulated experiment and the real experiment is sought with the parameter estimation algorithm. Soft biological tissue is modelled as a viscoelastic, non-linear, nearly incompressible, isotropic continuum. Viscoelasticity is accounted for by a quasi-linear formulation. The aspiration method is validated experimentally with a synthetic material. In vivo (intra-operatively during surgical interventions) and ex vivo experiments were performed on human uteri.
Assuntos
Algoritmos , Simulação por Computador , Tecido Conjuntivo/fisiologia , Aumento da Imagem/métodos , Modelos Biológicos , Anisotropia , Elasticidade , Feminino , Análise de Elementos Finitos , Humanos , Técnicas In Vitro , Teste de Materiais/métodos , Dinâmica não Linear , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Estresse Mecânico , Resistência à Tração , Útero/fisiologia , ViscosidadeRESUMO
Virtual reality (VR) based surgical simulator systems offer very elegant possibilities to both enrich and enhance traditional education in endoscopic surgery. However, while a wide range of VR simulator systems have been proposed and realized in the past few years, most of these systems are far from able to provide a reasonably realistic surgical environment. We explore the basic approaches to the current limits of realism and ultimately seek to extend these based on our description and analysis of the most important components of a VR-based endoscopic simulator. The feasibility of the proposed techniques is demonstrated on a first modular prototype system implementing the basic algorithms for VR-training in gynaecologic laparoscopy.