The Study Of 3D Surface Reconstruction System For Medical Images Based On ITK And OpenGL

3d reconstruction of medical image is processing a single or a sequence of human organ image which is obtained by imaging devices such as Computerized Tomography, Magnetic Resonance Imaging and Uhrasono graphy by computer in order to reconstruct 3d surface shape of the organ and furthermore rotate, zoom and cleave it via human-computer interaction. It is very valuable to research on fast and effective 3d imaging technique.ITK (Insight Segmentation and Registration Toolkit) has powerful function on medical image segmentation and registration and at present supports issuing using the form of open source so it is very popular in the developer staff. It has been and still will be the warehouse and the basis of segmentation and registration algorithm[1]. But because ITK does not have the function of visualization, generally it has to be used combined with VTK (Visualization Toolkit) to constitute a relatively complete medical image processing and analysis system. However VTK lacks flexible and practical user interface although it provides the visualization function. OpenGL is a set of 3d image database which is independent from operating system and has good cross-platform transplantation ability. With the development of graph display hardware, OpenGL has been considered as a standard by the majority of display card manufacturers and widely used in image visualization technology. In order to use the powerful function of VC++ 6.0 to realize 3d image rendering Windows provides OpenGL32.DLL and GUL32.DLL dynamic link library. Developers can conveniently program using graph library on many hardware platforms and operating systems and then obtain artistic and complex 3d color image.This topic realizes a new mode which uses ITK and OpenGL to develop a medical image processing platform. Under the popular programming environment VC++6.0, a sequence of DICOM image is input, divided and 3d reconstructed by ITK and then rendered and output by OpenGL. This mode not only solves the problem that ITK does not provide visualization but also customizes convenient and practical user interface according to needs.The main work of this paper is as follows:1 the extraction of iso-surface in ITKITK medical image segmentation and registration algorithms are abundant, but it only provides surface rendering algorithm to 3d reconstruction. Marching Cubes algorithm is considered as one of the most popular surface rendering algorithms, whose essence is to extract an iso-surface in a 3d data field, so it is also called"iso-surface extraction"algorithm. ITK iso-surface algorithm is realized by itkBinaryMask3DMeshSource. This topic considers the output of threshold segmentation as the input of iso-surface extraction, set a value via SetObjeCTValue(), the pixels whose gray value are equal to it are extracted directly and then an ITK data type Mesh whose Cell type is triangle forms. 2 interfaces of ITK and OpenGLOpenGL can render complicated and various shapes which are constituted by some base graph primitives. These base graph primitives include points, lines and polygons. Owing to that the result of ITK iso-surface extraction is a Mesh whose Cell type is triangle, there must be an interface for OpenGL. So the easiest method to render a whole Mesh is rendering all triangles one by one using OpenGL. And then OpenGL can be used once more to make the 3d scene more lifelike owing to its powerful rendering function.3 rendering of OpenGLMesh can be considered as a 3d point set whose points can also constitute Cells such as line segments and triangles as base units of Mesh. These Cells are preserved in memory in the form of linked list and can be accessed by Iteractor. Because all geometric graph primitives in OpenGL are described according to their vertex, we not only have to access every Cell but also have to obtain coordinates of all points by GetElement() when we want to render a triangle.