The Design And Implementation Of The System For Transformation From Computed Tomography Images To FEM Models

With the fast development of computer science, Finite Element Method (FEM) is becoming the most commonly used method in medical analysis to simulate and analyze biological tissues. In medical science, the imaging equipment such as CT can be used to obtain the interior structure of biological tissues and reconstruct the three dimensional FEM model. In bionics, simulation of the vibration of a bat’s vocal cord is necessary for the research of the efficient mechanism of bat’s giving off ultrasonic waves. Hence, build a FEM model of a bat’s vocal cord and study the characters and mechanism of its vibration are of practical importance.It is complicated to convert a cross-sectional image obtained by CT into an ANSYS FEM model, and those methods available are not efficiently and accurately enough. In this paper, a more suitable system is developed. Firstly, the cross-sectional data is processed using VTK.Then, the differences between structures of VTK data and ANSYS data are analyzed.Finally,the conversion system is designed according to these differences. The whole system is made up of four functional modules:the input module, data processing module, model converting module and the output module. This paper consists of the following five parts.1、Scan bats’ vocal cords with micro-CT, input the cross-sectional images into VTK and get the VTK data set.2、Resample the VTK data set to make a delicate model which can satisfy the needs of the memory. Then filter the gray values of VTK data set, for it is meaningful to filter the impurities and air around the model.3、Convert the VTK data into ANSYS model of three grid types. The three models are based on hexahedral mesh、 tetrahedral mesh and Ten nodes tetrahedron grid. The difference of nodes and units should be converted separately.4, Write dataset into an ANSYS data file. The ANSYS data file obtained is the FEM model. 5、Input the ANSYS data file into ANSYS software to build a FEM model,and then modal analysis is made to study the vibration features of the model.