A HYBRID FORMULATION FOR SOFT TISSUE MODELING ON REAL-TIME SURGERY SIMULATION
Mario Regino Moreno Guerra1; Paulo Henrique Junqueira Amorim1; Thiago Franco de Moraes1; Oscar Martínez Romero2; Alex Elías Zúñiga2; Eduardo Flores Villalba3; José Antonio Díaz Elizondo3; Jorge Vicente Lopes da Silva1; Ciro Ángel Rodríguez González2
1 Three Dimensional Technologies Division, Renato Archer Information Technology Center; 2 School of Engineering and Sciences, Tecnológico de Monterrey; 3 Medical School and Health Sciences, Tecnológico de Monterrey
doi:10.20906/CPS/CILAMCE2015-0633
Resumo
On the improvement of surgical training and planning methods, virtual reality and computational mechanics have been applied for the development of technological tools which aim to reduce patient risk in surgical procedures. A virtual reality system for surgery simulation integrates medical imaging, computational methods, material modeling and a mechatronic design of the interaction instrument. Modeling and simulation of soft tissue behavior is the main focus of this work. From materials point of view, soft tissues can be consider as composites, formed by an isotropic matrix and a bundle of reticular fibers with anisotropic behavior. To represent soft tissue behavior on virtual reality, it is needed a model that consider properties of anisotropy and non-linear deformation able to run on real-time simulations. In this article, a hybrid construction called Equivalent Spring-Mass Model (ESMM) is proposed. ESMM is based on an integration of the Spring-Mass Model (SMM) and an Equivalent Strain Energy Density (ESED) function. In this formulation, stiffness parameters of one-dimensional elements can be estimated at each stretch ratio to reach the same strain energy to the one calculated with a complex constitutive model on a pre-computational stage. The constitutive model defines the material response based on the interpolation of the isotropic and anisotropic volumetric fractions contributions, allowing the ESMM to represent an equivalent behavior on real time. The ESMM model was implemented in a virtual environment for laparoscopic surgery on a liver mesh segmented from medical images using InVesalius Software. The model parameters were calculated using experimental data of uniaxial tensile tests of porcine liver parenchyma. The ESMM elements shown good results and the estimations predict the real tissue behavior in an approximated way.
Palavras-chave: Soft tissue modeling; Virtual reality; InVesalius; Surgery simulation