HOU Hui-ling1,2
（1. Key Laboratory of Instrumentation Science & Dynamic Measurement (North University of China）, Ministry of Education, Taiyuan 030051, China; 2. School of Information and Communication Engineering, North University of China, Taiyuan 030051, China)
Abstract： Ring artifact is the major factor that seriously influence quality of computed tomography (CT) image reconstruction, especially in testing large-scale workpieces. To remove ring artifact quickly and efficiently, a kind of ring artifact correction method is improved based on the post-processing CT image reconstruction in this paper. At first, transform the CT image from the rectangular coordinates into polar coordinates. Next, design multidimensional filter to filter the image and calculate the mean and variance of each filtered pixel in polar coordinates. The location of artifact point is determined by the double precision. One is the comparison of calculated variance and variance threshold, and another is the comparison of pixel value and pixel value threshold. Then, process the artifact points in a reasonable manner and do details remain to CT image in particular. At last, convert corrected polar image into rectangular coordinates. The actual experiment shows that compared with the original method, improved method can better correct the ring artifacts and keep the image details for CT images. It is a kind of practical ring artifact correction methods for subsequent processing and quantitative analysis.
Key words： cone beam computed tomography (CT); Feldkamp-Davis-Kress (FDK) algorithm; ring artifacts; detail-preserving
CLD number： TP391Document code： A
Article ID： 1674-8042（2016）02-0165-06 doi： 10.3969/j.issn.1674-8042.2016.02.012
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细节保持的锥束CT环形伪影校正
侯慧玲1,2
（1 中北大学 仪器科学与动态测试教育部重点实验室， 山西 太原 030051； 2 中北大学 信息与通信工程学院， 山西 太原 030051）
摘要:环形伪影的存在严重影响CT图像重建质量， 特别是在大型工件的CT检测中尤为严重。 本文对一种重建后处理的伪影校正方法进行改进， 以快速有效地消除CT图像环形伪影。 首先， 将CT图像从直角坐标系转到极坐标系， 在极坐标系下设计多维滤波器对图像进行滤波处理。 计算滤波后每个像素的均值和方差， 通过计算的方差与方差阈值的比较以及像素值与像素值阈值的比较， 双重精确确定伪影点的位置， 对伪影点进行合理修正。 之后， 进行细节保持。 最后， 将校正后的极坐标图像转回直角坐标系。 实际CT实验表明， 与原方法相比， 本文改进方法能更好地校正环形伪影， 并保持图像细节信息， 是一种实用的环形伪影校正方法， 为后续处理和定量分析奠定基础。
关键词:锥束CT； FDK算法； 环形伪影； 细节保持
引用格式：HOU Hui-ling. Detail-preserving ring artifact correction method for cone-beam CT. Journal of Measurement Science and Instrumentation, 2016, 7(2)： 165-170. ［doi： 10.3969／j.issn.1674-8042.2016.02.012］
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