锥束射线RT扫描大视场三维CT成像方法研究

受探测器尺寸和重建锥角的限制,基于单圆轨道扫描和FDK算法的三维CT成像方法难以对大物体进行三维CT成像。提出了一种基于平板探测器,采用锥束RT扫描方式的成像方法,推导了其三维CT成像算法。首先把对回转物体进行三次锥束平移透照的投影数据重新排成为更大范围的倾斜平行投影数据,然后经过加权滤波和反投影重建,获得物体的三维层析结果。仿真结果表明,该方法在重构大物体图像时,获得了满意的图像质量。水平方向视场是单圆轨道FDK算法视场的2.88倍,在垂直方向减少了锥角过大形成的伪影,提高了物体的重构精度。

Three dimension imaging method based on cone beam-RT scaning mode

Since FDK reconstruction algorithm with circular orbit scan mode based on cone beam can only be used when the cone angle is small,the field of view is too narrow to scan large objects,a new reconstruction algorithm of 3D-ICT based on cone beam-RT(rotation and transverse) scaning-mode is developed.The first step, X-ray projection data were gathered by 2-D flat panel detector for three times in the horizontal direction,accompanied with the rotation motion in every horizontal locations.Further more the projection data are rebined to oblique parallel projection data.Then the data are back projectioned to the 3D-reconstruction image after the data have been preweighted and filted.Simulation experiment results show that the algorithm can acquire the satisfactory image quality with wider field of view in order to scan large objets.Analysis results show that the scaning field of view along the horizon can be improved to 2.88 times compared with classic FDK algorithm.