【作者】 赵明明；

【导师】 丁效华；

【作者基本信息】 哈尔滨工业大学 ， 计算数学， 2011， 硕士

【摘要】 恶性肿瘤是当今人类面临的一个非常严峻的健康问题,而肺癌是所有恶性肿瘤中对人类危害最大的。早期发现肺部肿瘤对肺癌的治疗意义重大,目前临床上主要采用X射线CT机检测早期的肺部病变,然而随着CT设备的不断改进,病人的CT摄片数越来越多,这不仅加大了医生的工作负担,也增加了漏诊和误诊发生的几率。本文研究了基于CT图像肺部异常阴影的自动检测技术,这也是肺部CAD系统中最关键的一部分。胸部CT图像中肺实质的分割是异常阴影检测的前提。本文首先通过边界跟踪算法与洪水填充算法提取出了CT图像中的胸部区域,进而从二值化后的胸部区域中找到初始肺部边界。为了保证分割出的肺部区域的完整性,本文提出了一种新的基于弧长表示的曲线平滑算法,用于平滑初始肺部边界,然后给出了一种新的边界修补算法,用于修补平滑后的肺部边界,最终实现肺部区域的完整分割。本文主要采用基于数学形态学膨胀运算的环形滤波器进行异常阴影的检测。文中首先介绍了二维环形滤波器的原理,为了过滤掉那些由血管造成的假阳性结果,本文将环形滤波器推广到了三维,然后针对环形滤波器的不足之处,提出了三种改进措施,最终得到了适应性更强的可变环形滤波器。本文对改进过程中遇到的图像距离变换问题还进行了深入的研究,给出了一种高效的实现二值图像欧氏距离变换的算法,同时还定义了一种新的路径长度,用以实现灰度图像的加权距离变换。实验结果表明,该检测系统可以大大减轻医生的工作负担。更多还原

【Abstract】 Malignant tumor is a very serious health problem for human beings and lung canceris the most harmful one at present. Lung nodule detection in early stage is very importantfor lung cancer treatment. And X-ray computed tomography (CT) is the most sensitivemodality for lung nodule detection in clinical. However, with the continuous improvementof CT equipment, it produces more and more images. Large amount of CT images notonly burden the image interpretation physician, but also increase the rate of overlook andmisdiagnosis. This dissertation focuses on computer-aided detection of lung nodules inchest CT images which is the most important part of lung CAD system.Segmentation of lungs from CT images is the precondition of lung nodules detection.At first, thorax region is segmented from the binarized CT images through border tracingalgorithm and ?ood fill algorithm. Then initial lung border is found in the binarized thoraxregion. In order to ensure the integrity of lung region, a new smoothing algorithm whichis based on the curve expression that take arc-length as a parameter is presented and it isused to smooth the initial lung border. Another lung border correction algorithm which isused to correct the smoothed lung border has also been proposed. At the end, lung regionis segmented completely.In this dissertation quoit filter which is based on Mathematical Morphology dilationis used to detect lung nodules. At the beginning, the principle of two-dimensional quoitfilter is introduced and then quoit filter is extended to three-dimensional in order to getrid of those false positive results caused by the vessels. For the inadequacies of quoitfilter, three improvements are proposed and ultimately obtained more adaptive variablequoit filter. The problem of distance transform of an image which is encountered in theimprovement process has also been studied in this paper. An e?cient Euclidean distancetransform algorithm has been given and a new path length is defined to achieve the gray-level weighted distance transform. Results of the experiment showed that this detectionsystem can drastically reduce the burden of the doctor.更多还原