The Key Techniques In Computer-Aided Aortic Aneurysm Surgery

Abdominal aortic aneurysm is a typical local malignant expansion of the abdominal aorta,which is in the need of customized medical peritoneal stent for endovascular interventional therapy.Thus it is necessary to estimate such as the diameter of the tumor,distance close to the descending aorta and the lower hip Arterial bifurcation angle and other important surgical parameters.Computer-aided diagnosis(CAD),as a technique developed rapidly in recent years,has been widely used in clinical diagnosis.Non-invasive,non-traumatic examination,which is represented by virtual endoscope,is more suitable for clinical examination of the tubular structure of human abdominal aorta.Therefore,this paper focuses on the research of key techniques from clinical data obtained for enhanced CTA to establish virtual endoscopic examination system.Since the original CT slice contains many irrelevant structures,there is some adhesion between the aorta and the surrounding tissue,and the individual difference of the patient.Therefore,it is necessary to segment the target area with efficient and convenient segmentation algorithm firstly.In this paper,the three-dimensional region growing method,the level set method for fast Marching solution and the level set method with prior shape detection are compared.The level set method can describe the change of the topological structure of the curved surface of the vessel wall in the three-dimensional space by the idea of surface evolution.And the shape constraint can overcome the problem of over evolution which may be caused by setting the evolution parameter on experience.As a result,the smooth and continuous target edge can be obtained.Based on the binarized data after segmentation,Boolean calculation can filter the background structure.At the same time,the virtual vascular model is reconstructed by 3D reconstruction technique,which is represented by surface rendering and volume rendering.Although volume rendering is able to fine structure of blood vessels,the rendering speed is slow.Although the surface rendering needs the appropriate algorithm to extract the target isosurface and generate the middle primitive representation of the triangular facet,it is faster and more suitable for the update screen rendering in the subsequent virtual roaming.Another key of virtual roaming technology is to automatically generate the optimal optimal continuous path,which needs to be as close as possible to the center of the pipe wall and to maximize the traversing of the whole blood vessel.In this paper,some typical centerline extraction algorithms are compared,such as topological refinement method,based on the shortest path method of axial surface.In order to overcome the shortcomings of the above algorithm,this paper introduces and implements an improved minimum cost path method based on boundary distance field.In this method,the minimum cost function is defined on the basis of the boundary distance change,and the numerical solution is obtained by the gradient descent method.The approximate approximate center path can be obtained by the method,which can be treated as path of virtual roaming after post procedure like smoothing.After setting the parameters of the virtual camera,it is possible to realize automatic roaming of the blood vessel inner wall.The major advantage of Computer-aided diagnosis is that you can use three-dimensional visualization technology to simulate the human organ,to solve the preoperative planning of the lesion parameters of interest measurement problems.And the position and shape parameters of the target are repeatedly obtained by the interactive operation,in particular,the virtual slice is constructed at any angle and position,and the diameter of the tumor is obtained with the primitive voxel mapping;and the bifurcation angle of the hip artery is fitted with the centerline And the interactive measurement method.All of above parameters are important for doctors to develop treatment options.In this paper,an integrated diagnostic system is constructed.The operator can achieve segmentation,reconstruction,virtual endoscopy and interactive measurement of the abdominal aorta and tumor,and obtain satisfactory results.