3D Reconstruction And Key Technology Study For Slice Medical Images

At present,image data visualization,especially visualization of medical image (such as computed tomography(CT) and magnetic resonance imaging(MRI)),has become one of the hotspots of image processing research after more than two decades development.Three-dimensional(3D) reconstruction is the most intuitive method of the medical image visualization.In order to achieve 3D reconstruction of the medical images,we must process images first.So we can detect the contours of the interested templates,organize and pathological area easily.Then,we can achieve the 3D reconstruction of the extracted organs,tissues or body lesions,and get the purpose of adjuvant therapy,surgical planning,teaching model and prosthetic design. In medical diagosis and surgical planning,3D figure model of the sick organization is generated by the application of reverse engineering.Further,operation model is producted by the use of rapid prototyping technology.On the basis of the model, doctor achieves diagosis and surgery,which effectively improve the level of diagnosis and surgery,shorten the time,save the cost,and improve the safety of surgery.The center issue of this thesis is the 3D reconstruction of medical slice-images.In this paper,we begin with an introduction to reverse engineering and 3D reconstruction technique of medical images,and we introduce the collection methods of slice-images data.Then,we introduce the methods and research status of digital image processing,medical image reconstruction and CAD models conversion.We mainly research and implement the methods and related technologies on the extraction of contour lines of medical slice-images and geometric surface reconstruction,which includes image enhancement and noise reduction processing of slice-images,edge detection and contour extraction,surface reconstruction algorithm,and the conversion of 3D model surface.According to the low contrast,noise and slow changes of medical images,a gray balance algorithm is used for pre-processing,that can improve image contrast. Then,combining median filtering with wavelet transform to enhance and denoise image.The results show that the algorithm achieves good effects,and can deals with low quality or marginal vague images.Contour extraction is one of the main pretreatment process of the 3D reconstruction.Using of improved Canny edge detection and boundary tracking,the paper proposed a image contours extracted method,thus propose a single pixel and closed contours.In Chapter 4 of the paper,we introduce the basical theorey of surface reconstruction-the knowledge of B-spline curves and surfaces,and the definition, properties,calculation and backcalculation methods of curves and surfaces.Then, the surface reconstruction method-based on the B-spline surface reconstruction were studied.Fist,the paper analyse the key technologies of data points accessed, including the selection of feature points and the establishment of sampling points. Besides,we extracted feature points based on curvature feature,and resampled feature points in order to get a unification sampling points in each line(column). Then,we interpolated sampling points to get a bi-cubic non-uniform B-spline surface.Finally,we inserted nodes on the surface based on distance feature under the certain control accuracy,and calculated the new control points through the least-squares approximation method,to get approximate surface within the permissible range error.Based on the characteristics of slice contours,we integratively used B-spline cycle and non-cycle B-spline,and discussed how to calculate closed and non-closed surface.In addition,the combination of interpolation and approximation reduces the computational complexity.Finally,the paper studied the conversion process from the surface model to the CAD model.Then,the paper studies the two key technical issues of surface reconstruction—matching and branch.First,the paper gives the methods of many surfaces reconstruction and nested surfaces reconstruction:Through the establishment of tree contour,we recognize the in-out features of contours and the outline of the relationship between the contours,and reduce the searching range.Based on tree contour,we find marching contour by use of the threshold radius to determine the correspondence contour on the adjacent sections.Second,the possible problem of branch was studied.Using weight segmentation method,combined with interpolation,we separated the mother contour to solve the branch problem and reconstruct surface.