Rapid prototyping applications in medicine. Part 2: STL file generation and case studies

Rapid prototyping (RP) technology has extended traditional manufacturing ap plications in areas other than product engineering. Using RP to fabricate c ustom implants and prosthesis for surgical planning and education is now an important area of research. Although, in theory, RP is capable of producin g objects of any complexity, designing freeform shapes is difficult using c urrent CAD systems. These CAD systems are geared toward the design of parts manufactured by traditional methods; they do not help designers exploit th e expanded opportunities offered by RP technology. Medical data cannot be i nput into these CAD systems directly for further modification and manipulat ion. The purpose of this project is to explore a new approach for modelling and prototyping biomedical objects. The work extends from volume modelling to RP and medicine. In Part 1 of two papers, a new approach to modelling complex objects, NURBS -based volume modelling, is proposed. A NURBS representation of volumes is developed to represent not only the surface boundary but also the interior of a 3D object. NURBS-based volume modelling inherits advantages from both NURBS modelling and voxel-based modelling. The key idea of the NURBS-based volume modelling is to exploit the flexibility of NURBS modelling and use t he voxelised NURBS volumes as components for constructing complex objects. This paper, Part 2, deals mainly with issues of interfacing volume models t o RP systems. A new approach to generate STL files through volume modelling and iso-surface extraction is proposed. This approach guarantees the valid ity of the final STL file inherently. Software development and case studies are also given.