3-D Reconstruction Of Blood Vessels Skeleton From Biplane Angiography System

Digital subtraction angiography (DSA) is a widely used technique for the visualization of blood vessels in the human body which has significant values in the diagnosis and therapy of all kinds of vessel diseases. How to accomplish three dimensional reconstruction of vessels to provide more powerful diagnostic value is still an active research topic in the field of medical imaging. In this thesis, three dimensional reconstruction problems in biplane angiography technique are discussed which includes two situations: 1) the two images obtained in unknown orientations. 2) the two images obtained in exactly known orientations. And before reconstruction, the skeletons of the vessels are extracted by Multiple Gabor Filter.In the first situation, an 8-points algorithm using linear approach is employed to estimate the biplane geometry of the images. As a result of the instability of the estimation of the fundamental matrix with this method, errors are caused by assessing the essential matrix through the fundamental matrix with unknown camera intrinsic parameters. A simple method is applied to modify the essential matrix. Constrains are found from the characteristic of the rigid rotation matrix.In the second situation, two efficient methods are proposed which are different from the traditional reconstruction method which is based on geometry of perspective projection. One is the method based on neural network. In this method, neural network is utilized to build the relationships between the 3-D points and 2-D points based on B-splines. By feeding the corresponding control points into the neural network, the 3-D blood vessels represented by B-spline can be obtained. The other is the reconstruction method based on snake model. 2-D snake is extended to 3-D snake in the space to represent the initial contour of the skeleton of the blood vessel. Bifurcations on blood vessel's skeleton are chosen to optimize GT (Geometry Translation) matrix. GVF (Gradient Vector Flow) is utilized as external energy of 3-D Snake The Snake iteratively evolve towards the true configuration of the blood vessels, satisfying the constraint of being smooth. The result of experiments indicates: Compared with traditional way, user interaction is reduced and reconstruction performance is improved by this method.