【作者】 郭明焕；

【导师】 张书玲； 张朋；

【作者基本信息】 西北大学 ， 基础数学， 2002， 硕士

【摘要】 计算机层析成像技术(简称CT)是近几十年来发展起来的一种新的无损检测技术，具有检测精度高、重建图像无影像重迭、空间分辨率和密度分辨率高、可直接进行数字化处理等优点，现已被广泛应用于航空、航天、机械、船舶、公安、海关、医疗等诸多领域。 本文的主要假设是线阵列探测器可沿其所在的直线或圆弧移动，且移动步长小于线阵列探测器的探测器宽度，由此就可以通过相叠采样采集到相叠低分辨数据。 本文在研究插值代数重建法(IART)的基础上，根据特别设计的数据采集模式(平行相叠采样和扇形相叠采样)，提出了由相叠低分辨数据重建高分辨图像的两个新算法，即虚拟探测器法和直接重建法。这两个算法对于不同的相叠采样模式，具体表现为四个算法：平行束的虚拟探测器法、平行束的直接重建法、扇形束的虚拟探测器法和扇形束的直接重建法。 大量模拟试验结果表明，无论对平行束的相叠低分辨数据还是对扇形束的相叠低分辨数据，用虚拟探测器法和直接重建法均可由相叠低分辨数据重建出具有较高分辨率的图像。其中用虚拟探测器法重建的图像的分辨率非常接近于由高分辨数据直接重建的图像的分辨率。虽然直接重建法重建的图像的分辨率略低于虚拟探测器法重建的图像的分辨率，但该算法可适用于任意的相叠采样数据。更多还原

【Abstract】 Computed Tomography technique(CT) has become a new nondestructive detection method in recent decades. The images reconstructed by CT are of good quality and high resolution. Furthermore, CT images can be processed and analyzed digitally. So CT is widely applied in aviation, astronautics, mechanics, shipping, public security, customs, medicine, and many other areas.The main assumption in the paper is that the linear array of detectors can shift along the line(or arc) of the array with a step which is less than the width of the detectors, and the overlapped low-resolution projection data can be collected by overlapped sampling.In this paper, two novel algorithms of reconstructing high resolution images from both overlapped parallel projection data and overlapped fan beam projection data with low resolution are presented. One is called virtual detector algorithm, and the other is direct reconstruction algorithm. Both of the algorithms with two forms for the parallel data and fan beam data respectively are developed based on the interpolative algebraic reconstruction techniques (IART).The simulation results show that, either for parallel geometry or for fan beam geometry, high resolution images can be reconstructed by means of both the algorithms from the overlapped projection data. Moreover, the quality of the images reconstructed by the virtual detector algorithm from the overlapped low-resolution projection data is almost as good as that of the images reconstructed directly from the high-resolution projection data. Although the resolution of the images reconstructed by the direct reconstruction algorithm is slight lower than that of the images reconstructed by thevirtual detector algorithm, the direct reconstruction algorithm adapts to any kind of overlapped projection data.更多还原