基于正弦图的投影旋转中心校正方法

Correction Method of the Projection Images' Rotational Center Based on Sinogram

CT转台受仪器精度等影响会导致投影旋转中心偏移,这将严重影响重建图像的质量。因此,在CT重建前,投影旋转中心的精确校正是必不可少的。根据radon变换推导了平行束扫描模型投影旋转中心的计算公式,确定了正弦图中0°和180°的样本投影地址均值的一半就是投影旋转中心的地址。根据上述方法,将sino图中0°和180°对应的数据各复制N次得到图像矩阵A,同时采用"Chan-Vese"对其进行二值化分割,得到0°和180°样本投影地址并计算投影旋转中心,最后以此为中心对sino图在水平方向上裁剪进行校正。通过仿真和真实实验,表明该方法能够高精度地校正投影旋转中心,有效地提高重建图像质量。

Affected by the precision of instruments and other factors,CT turntable may cause the deviation of projection center of rotation(COR),which will seriously affect the quality of the reconstructed images.Thus,the precise correction of COR in projection images plays an important role in the CT reconstruction.In this paper,a method of measuring the address of COR is proposed based on the radon transform,which is suitable for the parallel beam scanning model.The method can be summarized as follows:the COR address of the projection is obtained using one half of the meanof the0°and180°projections'addresses in sinogram.According to the method,the data,whichrepresent0°and180°projections in sinogram,were respectively copied by N times to get the image matrix A.The image matrix A was then segmented into binarization with the“Chan-Vese”method,and the0°and180°projections'addresses of sample were obtained to calculate the COR address of the projection.Finally,the COR value was regarded as the center of the sinogram,and the sinogram was clipped properly in the horizontal direction.The simulation and experiment show that this method can accurately correct the COR,which effectively improves the quality of the reconstructed images.Method can accurately correct the COR,which effectively improves the quality of the reconstructed images.