Study On 3D Reconstruction For RPM Based On Medical Slice Contour Image

Rapid Prototyping Manufacture technology is a high-tech developed in the late 80's, which integrates New Material Science, CAD, Numerical Control and Laser Technology. By using it, 3D objects with complex figure can be fabricated rapidly, easily and precisely. So the technology will be used widely in medical field. Computerized Tomography technology is always powerful means to examine bones with pathological changes and replace it. How to combine this two technology well for fabricating made bone model and bone substitute rapidly and precisely, which is public concern for a long time.For solving this problem, the paper has brought forward a new way which generates directly STL data of 3D objects model by interbedded interpolating based on CT contour BMP. Firstly, using the contour tracing algorithm to trace the manipulated contour BMP, it has attained the contour point chain recorded by Chain Code. According to the character of slice contour, the paper has brought forward a new selecting initial point algorithm which is based on the changing-rates of point and threshold between two points. Then, it interpolates the contour character point with the third power cycle non-uniform B-spline to make slice contour into vectorgraph.In 3D reconstruction of serial slice images, the orientation of slice contour is a key problem. Because the public barycenter of organism slice contour is continuous, the paper move the public barycenter of upper slice to the place of nether one, then calculates the least distance of these corresponded contour in the process of moving upper slice around the superposition point, so attains the best orientation. Accounting for the larger distance of CT images, the paper uses its optimized least distance algorithm to attain lengthways contour point chain which is interpolated with the third power non-uniform B-spline. Using the Z-plane in the middle of two slice to intersect these lengthways contour line, it has attained the contour character point on the middle slice which is middle layer information of model.Lastly, conforming to the STL triangular facet rule, the paper links the contour character point on the adjoined slice to generate triangular facet model based on directed graph principle and the least internal angle being the largest rule of Delaunary triangulation. The triangular facet model is also the STL data of model. According to the request of STL file format, it writes the STL data into STL file which is the initial data of Rapid Prototyping Manufacture.