Anatomical Model Reconstruction (Solid Modeling) Using a Reverse Engineering Approach

In addition to the traditional applications in computer-aided systems such as machining and finite element analysis, solid modeling is nowadays utilized for various purposes in medical applications such as the design of implants and prostheses or quality control, verification, and analysis purposes. This is mainly because solid models provide properties such as mass and volume and can be used in mechanical assemblies. In the case of either designing or reconstructing medical applications, certain techniques are used to account for the missing information. This is not only due to insufficient scanned data but also due to missing information in cases where there are defective organs or bones, such as the anatomical reconstruction of defective skulls. Common techniques involved are mirroring, surface interpolation, deformed template, and slice-based reconstruction. In medical applications for designing and reconstruction purposes, the techniques that have been mentioned are surface fitting, contour skinning, volume polygonization, and implicit-function interpolation. In this study, the basis for solid modeling is an STL file that was obtained from 3D scanning as a reference. The Human Femur bone model is constructed from a DICOM file, which is converted to a 3D model, exported as a.stl file, and then printed. The model is 3D printed on Stratasys fused deposition modeling 3D Printer and scanned back using a handheld 3D Scanner. In this work, FreeCAD software was used for solid modeling. FreeCAD is commercially available open-source software that can be used for parametric 3D modeling, mesh manipulation, and repair, finite element analysis tools, robot simulation modules, and computer numerically controlled workbenches. The method proposed in this study is direct lofting of cross-sections of the mesh and taking advantage of the FreeCAD workbench to convert individual lofts to solids. Thereafter, a single solid model was created using Boolean functions.