锥束工业CT射束硬化校正方法

摘要

锥束X射线CT系统中,X射线束具有宽能谱的特性,会导致X射线硬化效应的产生,从而使得重建图像中出现杯状和条状伪影等,故有必要研究硬化校正方法以减少硬化效应带来的影响.提出了基于试验能谱和蒙特卡罗模拟的多项式拟合硬化校正方法,基于试验测量X射线初始能谱,利用蒙特卡罗模拟得到透射厚度与多能投影的关系,再利用多项式拟合得到多能投影与等效单能投影的转换关系,从而实现硬化校正.分别采用该方法和传统的滤波片法对一铝制标准件进行射束硬化校正试验.结果表明,所提出的方法比滤波片法能更好地消除锥束CT的硬化伪影.%Since the X-ray beam has the characteristics of wide spectrum in the cone beam X-ray computed tomography imaging system, this leads to the X-ray hardening effect, so as to make the reconstruction image in the goblet artifact and strip artifact.It is necessary to study methods of the hardening correction in order to reduce the effects of hardening effect.A method of beam hardening correction is put forward, which is based on the experimental spectrum and Monte Carlo simulation of polynomial fitting.Based on the initial X-ray energy spectrum by experimental measurement, the relationship between transmission thickness and pluripotent projection can be obtained by exploiting Monte Carlo simulation. And then using polynomial fitting can obtain relationship between pluripotent projection and equivalent single projection, so as to realize hardening correction. This method and the traditional filter method for X-ray hardening correction on the aluminum workpiece were respectively used. The experimental results show that the proposed method is better than the filter method which can decrease cone-beam CT beam hardening artifacts effectively.It provides an effective correction method for cone beam industrial computed tomography beam hardening correction.