摘要
对表面法向量投影叠加法进行改进,提出一种基于三维局部形状约束并采用自适应投影距离的表面法向量叠加疑似肺结节检测方法。现有的表面法向量投影叠加法没有对初始ROI(region of interest)区域表面进行形状约束,采用单一投影距离,存在投影叠加计算量大且只适用于固定大小的肺结节检测问题。首先采用Otsu阈值方法得到初始ROI区域,计算初始ROI曲面的三维局部形状指数,对三维ROI的体素表面法向量进行投影约束,以提高球形选择性、减少投影叠加计算量;在表面法向量叠加过程中由ROI曲面自适应地决定投影距离,一方面限制表面法向量向ROI曲面外投影;另一方面可以克服检测固定大小肺结节的局限性;由于肺结节一般表现为球形,具有较大的表面法向量投影叠加值,选择局部最大叠加值,可以检测不同大小的球形疑似肺结节区域。实验结果表明,改进算法具有更好的球形选择性,可以较好地检测出不同大小的疑似肺结节,具有较高的敏感度和较低的假阳性率。
An improved surface normal overlap algorithm for suspected pulmonary nodule detection is proposed in this paper. The improved surface normal overlap detection algorithm is based on local 3-D shape constraint and adopts adaptive distance projections according to surface of original ROI. Existing surface normal overlap algorithm has no shape character restriction on RO1 surface and projection distance is fixed, it may fail to distinguish between a small size sphere object and a much larger size non-sphere object, and is also time-consuming. So, existing method is only applicable to the nodules with fixed size. In this paper, Original region of interests in pulmonary parenchyma is seg-mented with adaptive threshold method. Voxel surface normal of original ROI is constrained in projection. Local 3-D shape character is used in the courses of projection overlapping, which enhances the capability of sphere selection and increases the effect of projection overlapping. Surface of original ROI decision-making projection overcomes the limit of detecting fixed size nodules, prohibits the projection outside the original ROI. So the suspected lung nodules can be detected with local maximum method. Experiment results indicate that the improved algorithm has the ability of sphere selection, can detect suspected pulmonary nodules effectively, and has higher sensitivity and lower false positive rate.
出处
《仪器仪表学报》
EI
CAS
CSCD
北大核心
2011年第12期2787-2793,共7页
Chinese Journal of Scientific Instrument
基金
国家自然科学基金(60671050)
中央高校基本科研业务专项资金(N100404010)资助项目
关键词
疑似肺结节
法向量投影叠加
局部三维形状约束
曲面决策投影
suspected pulmonary nodule
normal projection overlap
local 3-D shape restriction
surface decision-making projection
