工业CT射束硬化研究

RESEARCH OF BEAM HARDENING OF INDUSTRIAL COMPUTED TOMOGRAPHY

针对工业CT(industrial computed tomography,ICT)使用的X射线为一种多能谱射线,分析这种X射线对物体进行断层扫描时发生硬化的机理及其对重建结果的影响,推导出用于校正的数学模型。利用仿真手段对该数学模型进行验证。仿真和实验结果表明,该数学模型对射束硬化可起到较好的校正作用。为高精度工业CT设计提供一定的理论基础和方法。

The X-ray used in ICT（industrial computed tomography） is multi-energy ray. The cup artifact image will appear when object is scanned by the X-ray. Because the high energy X-ray has stronger penetrability than low energy X-ray, the low energy X-ray will be absorbed easily. The principle of beam hardening and the results of affecting to reconstruction were analyzed. Then deduced the exponential mathematical model to calibrate the beam hardening and applied the model on emluator of ICT which have been developed. The beam hardening is corrected mostly. The depth of cup is only 10% - 15% comparing to that before calibration. In the experiment of scanning cylinder, the beam hardening artifact is weakened, In practical application, there are many factors which can bring artifacts. The beam hardening artifact isn＇t been eliminated in the scanning cylinder experiment because only beam hardening is considered. The results of test prove the model useful. In the ICT system developed, the calibration model is integrated into successfully.