CT系统参数标定及成像

Parameters Calibration and Imaging for CT System

针对CT系统旋转中心、探测器单元距离、射线方向的标定问题,首先建立原点在椭圆中心的平面直角坐标系,给出射线穿过介质的长度与射线方向、探测器单元距离和原点到射线的最远距离三个参数之间的解析关系式;然后利用接收器吸收信息与对应射线穿过长度成比例这一条件,可得每次旋转时相邻两个接收器接收信息的比值与它们对应射线穿过长度的比值在理论上相等,从而以这两个值的最小二乘误差为目标函数建立非线性规划模型,求解得到单元距离和旋转的射线方向,进而标定CT系统的参数。针对CT系统接收器接收信息的还原问题,建立了利用Radon反变换进行求解和切线区域取交集法进行验证的复原模型。

This paper is concerned about the rotation center,detector unit distance and ray direction of the CT system.First,a plane orthogonal coordinate system with the origin at the center of the ellipse is established.The analytical relationship between the length of the ray passing through the medium and the ray direction,the distance between the detector unit and the three parameters from the origin to the ray is given;Then the ratio of the information received by two adjacent receivers at each rotation is theoretically equal to the ratio of their corresponding rays through the length,using the receiver absorption information and the ratio of the corresponding ray to the length of the ray.Taking the least square error of the two values as the objective function,the nonlinear programming model is established to obtain the ray direction of the unit distance and rotation,and the parameters of the CT system are calibrated.In view of the reduction of receiver receiving information in CT system,a restoration model is established by using Radon inverse transform to solve and verify the intersection method of tangent area.