R&D Of 3d Reconstruction System From Medical Images Based On Rapid Prototyping

Rapid Prototyping (RP) is an advanced forming and processing technology that is followed with interest by researchers and manufactures in recent years. The integration between RP technology and CT technology in medicine have a strong impact on physic. It can meet many different needs in physic by reconstructing 3D medical objects from medical images, and manufacturing the prototype of tissue object of patient by using RP technology. 3D reconstruction from medical images is a focus problem of researchers at present, and it has many important applications in diagnostic, surgery planning and simulation, plastic and artificial limb surgery, radiotherapy planning, and teaching in anatomy. So, study on 3D reconstruction from medical images has important significance on science and worthiness in practical application.This dissertation, mostly studies the technology of 3D reconstruction from medical images. The main contents of 3D reconstruction from medical images include input of medical image, pre-processing, such as filtering and interpolating, segmenting and extracting tissues or organs of body, constructing 3D surface models. Key technologies for 3D reconstruction are studied in this dissertation, and a interface software between CT system and rapid prototyping system is exploited else.DICOM file is the main file format of medical image, and input module of it is exploited. Some filtering methods and interpolating methods, such as liner interpolating, elastic interpolating based on matching and interpolating based on contour, are discussed. Through comparing these methods, liner interpolating and interpolating based on contour are chosen.Exact segmentation is a precondition that reconstructing model can represent tissue and organ exactly. Owing to inapplicability of segmenting, which there is no universal method which can be applied in every image segmenting, a corresponding segmentation method is presented. The segmentation process consists of following steps: creating the threshold values after analyzing the gray-level histograms of the whole 3D image and some slice images; choosing the threshold values interactively after researching the gray values around the contour between two different tissues; binarizing the images using the threshold; processing the images using properly mathematical morphology operation according to the feature of tissues or regions to extract; and filling the regions using seed fill algorithm.Marching cubes (MC) algorithm is a classical algorithm to extract iso-surface from regular volume data, and marching tetrahedra (MT) algorithm is improved based on MC algorithm. This dissertation has implemented these two algorithm to extract iso-surfacefrom the segmented regions. 3D surface models are built up. MT algorithm has disadvantages of low reconstructing speed and data redundancy. To improve this algorithm performance, methods to deal with the relativities among tetrahedral in one voxel and relativities among voxels are developed. With the methods, repeated interpolating calculation is avoided, and surface reconstructing is speed up.At last, this dissertation introduces the exploitation of the interface software between CT system and rapid prototyping system. Several functional modules is plotted out, procedure of the software is analyzed and corresponding process is created. This software provides the functions for inputting of medical images, pro-processing, segmenting and interpolating, exacting iso-surface, storage of volume data and STL file which is a de facto inputting format of RP system, and so on.