3D Visualization And Medical Image Analysis Techniques In Abdominal Aortic Aneurysm Operation

Abdominal aortic aneurysm(AAA)is a localized enlargement of the abdominal aortic.The aneurysm expands gradually until rupture with up to 90% mortality rate.Clinically,the stent interventional procedure is an effective means of treating the disease.The procedure requires clinicians clearly understand the morphology and anatomical structure of abdominal aorta and the aneurysm,accurately measure the maximum diameter of the aneurysm,and accurately measure the iliac artery bifurcation angle for choosing the proper stent type.In this paper,visualization and medical image analysis techniques are used on CTA images to provide required information for the stent interventional procedure,which develops the preoperative computer-aided analysis system as well as enhances the safety and reliability of the operation.This paper focuses on information requirement issues in three aspects related to abdominal aortic aneurysm operations to research on.Firstly,segmentation and three dimensional reconstruction of the abdominal aorta are studied.The morphology variety of aorta among patients,the disturbing bifurcations and anatomical structures around the aorta bring much difficulty for the segmentation of the aorta.Therefore,in this paper,the Fast Marching level set method is used to segment the abdominal aorta and the aneurysm,which can naturally deal with the topological changes during the evolution of surfaces as well as the interference of gray scale and noise,and result in closed surface models.Then,we use surface rendering method to extract the surface of the abdominal aorta and the aneurysm which is smoothed later,and effectively reconstruct the abdominal aorta and the aneurysm.Secondly,the centerline of the abdominal aorta and the aneurysm is extracted,on basis of which virtual roaming is realized to achieve internal observation of the aorta and the aneurysm.The centerline is extracted by first computing the Voronoi diagram of the aorta surface model as approximation of the medial axis and then computing the minimum cost path between the starting point and the ending point on the medial axis using Fast Marching algorithm.By taking the extracted centerline as roaming path and determining parameters of the virtual camera,the internal virtual roaming of aorta and the aneurysm is achieved.Finally,we provide methods to measure concerned parameters in the abdominal aortic aneurysm clinical diagnosis and operation.The measurement of maximum abdominal aortic aneurysm diameter is realized by virtual cutting of the aorta and measuring on slice generated by the cutting plane.The iliac artery bifurcation angle is measured using principle direction calculation of the bifurcated centerlines.The techniques and the computer aided analysis system of this paper has been applied to practical CTA images and accepted by clinicians.Therefore,they can be used to enhance the safety and reliability of the stent interventional procedure.