【正文】 print Images,” Journal of Software, 2020, 14(6):10821088. [5] LIANG Guangmin, CAI Xuejun, “Improvement of OPTA algorithm and its application in fingerprint images thinning,” Computer Engineering and Design, 2020,27(23):46074608. [6] Zhang YuJin, Image Engineering (II): Image Analysis(second edition), BeiJing:Tsinghua University Press, 2020. [7] XU Gangfeng, WANG Ping, SHEN Zhenkang,“Recognition of mainrunway of airport based on skeleton,” Infrared and Laser Engineering, 2020,35(6):717721. [8] ZHANG Jinyang, SUN Maohang, “Study on algorithm for skeleton features extraction of hand vein image,”Journal of Computer Applications, 2020, 27(1):152154. 11 Research on Cerebral Aneurysm Detection Based on OPTA Algorithm Abstract—It is the key step of the cerebral aneurysm recognition system to locate the cerebral aneurysm accurately and fast onto the image. A new detection method of cerebral aneurysm, which is based on the improved thinning algorithm, is proposed after analyzing the morphological characteristics of cerebral aneurysm fully in the paper. In this new detection method, the improved OPTA algorithm is used to get the skeleton tree of blood vessel firstly, and then cerebral aneurysms are detected by searching the skeleton tree. After doing lots of experiments, the cerebral aneurysm can be detected well by using this new method, which provides a premise for cerebral aneurysm recognition. Index Terms—OPTA, thinning algorithm, cerebral aneurysm detection, template matching I. INTRODUCTION Cerebral vascular disease, especially cerebral aneurysm is one of the key factors leading to disease and death in adults, which threaten the health and life of human badly. With the development and the unceasing maturation of puter technology, CAD(Computeraided Diagnosis) System resulting from the bination of information technology and medical imaging technology plays a more and more important role in detecting and treating cerebral vascular disease, and it has already bee a research focus in medical imaging. The cerebral aneurysm usually was located in the bifurcation position of vessel, especially the cerebral artery circulus, and the reason is that the impact of blood flow has great influence on the bifurcation position. Cerebral vascular image is similar to river work, and there exists artery and many other branch vessels. Generally, vessel is approximately symmetric, whose two edge contours are approximately mutual parallel. But cerebral aneurysm is the projecting part of the vessel edge caused by lesion. The schematic diagram of cerebral aneurysm is showed in Figure 1. From Figure 1, the position marked by pane is cerebral aneurysm. The projecting part has appeared in the normal vessel and the approximately parallel of two edge contours is broken. The lesion site was manifested as obvious branch structure. So we can ascertain the lesion site of cerebral aneurysm by detecting the branch structure in vessel skeleton tree. 12 Figure 1. The schematic diagram of cerebral aneurysm In the cerebral aneurysm CAD system based on DSA(Digital Subtracted Angiography), it is the premise and important step of feature extraction and recognition to detect the position of cerebral aneurysm in DSA. This paper analyzes morphological characteristics of cerebral aneurysm, obtains the topological skeleton tree via the improved thinning algorithm, then does depthfirst traversal search on skeleton tree, and lastly detects the position of cerebral aneurysm. II. OPTA ALGORITHM OPTA(Onepass Thinning Algorithm) is a typical templatebased image thinning algorithm, whose core is thinning processing by the application of elimination template and preservation template. OPTA is an iterative process. If the current point satisfies the elimination template and doesn39。 q6=1 amp。 q9=0 amp。 q14=0) (4) (q8=1 amp。 q10=1) || (q3=1 amp。 q13=0 amp。 q11=0) (7) p=1 (8) Among them, p is the current point and Figure 5 shows q1~15. Though at present, improved OPTA is only applied to the thinning of fingerprint image [4~8]. This paper applied the above and improved OPTA to skeleton extraction of cerebral vascular image. By many experiments, we found that the burr of vascular skeleton extracted by original OPTA is a bit more, so it cannot be used in the detection of cerebral aneurysm. The effect of document [1] is much better, but the thinning speed is not ideal. Though the thinning speed of document [2] was increased significantly, the breakpoint phenomenon produces easily while thinning vessel. Through weighing various f