双CCD拼接CT成像的断裂伪迹消除方法  

Method of eliminating the fracture artifact of twin CCD detector CT

作　　者：方正[1] 骆清铭[1] 

机构地区：[1]华中科技大学生物医学光子学教育部重点实验室-武汉光电国家实验室(筹)生物医学光子学研究部,武汉430074

出　　处：《光学技术》2007年第6期863-866,共4页Optical Technique

基　　金：国家自然科学基金资助项目(90508003);教育部科学技术研究资助项目(重大10420)

摘　　要：为了解决双CCD拼接的探测器CT在成像时的几何失真问题,以双CCD探测器数字X射线机FAXITRONMX-20为实验对象,利用矩形钢板的二维投影图像计算出两块CCD之间的横向和纵向位移偏差,并以此为依据对所拍摄的图像做相应的平移和插值处理。利用金属球模型的二维投影图像分别计算出射线源垂直投影时位于两块CCD平面上的坐标,并以此为依据调整CT投影图拍摄的旋转中心。结果表明:利用矩形钢板的二维投影图像计算出的两块CCD之间的横向位移达到3个像素;利用金属球模型的二维投影图像分别计算出的射线源的垂直投影位于左、右两块CCD的平面坐标上。根据这些测量数据调整了拍摄方法,修改了重建软件,并以模型实验显示了校正前后的结果。该方法考虑了双CCD探测板之间的缝隙和空间不共面的情况,减轻了三维重建在拼接处的"断裂"现象,使得纵向误差由88μm减小到了44μm。Distortion appears in CT imaging when the detector is composed of several CCD arrays. The gap between adja- cent CCD arrays and their coplanarities should take into account. Projection of a rectangular armor plate is used to measure the landscape orientation and portrait orientation error. The measured distance between these two plane detectors is about 3 pixels＇ wide. Central difference interpolation is used to remedy this error. The method of calculating the coordinate of X-ray source through a metallic ball model＇ s two dimensions projections is represented. Coordinate of the source can be calculated through projective lines. The axis-of-rotation （AOR） is positioned according to the calculated coordinate of the source. Model test is per- formed to show the effect of the amelioration. This method can reduce the rupture of reconstruction between these two CCD ar- rays. The longitude error is reduced from 88μm to 44μm after algorithm amelioration according to the calculation above.

关 键 词：X射线光学 伪迹 锥束CT 平面探测器 双CCD 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]