工业CT用X射线机射线强度分布研究

Study on the distribution of radiation intensity of X-ray machine for industrial CT

X射线机是工业CT中使用最广泛的X射线源,但因阳极效应以及自身结构的限制,其射线强度空间分布不均匀,系统的研究和测量其射线强度分布对于实际应用十分必要。利用Cs I(Tl)光电二极管探测器测量了射线强度在不同轴线上随角度的分布,给出了理论分析,并与蒙特卡罗法计算结果做了对比,提出了"展宽效应",解释了边界射线强度分布展宽的现象。比较了大、小焦点射线强度分布的情况,给出了其在阴极末端出现差异的原因。结合其在竖直方向的射线强度分布以及对称性,给出了X射线强度的二维分布。结果表明,在张角20°(10°+10°)的范围内,射线强度分布均匀(最大相对偏差4.59%),张角越大均匀性越差,在阴极端边界射线分布出现外延。

Background： X-ray machine is the most-extensively-used X-ray source in industrial CT, due to its anode effect and the restrictions of its own structure, the radiation intensity distribution is not uniform. Purpose： The aim is to research and measure the radiation intensity distribution of X-ray machine as a vital part of imaging correction and the foundation for the precise application of X-ray machine. Methods： The CsI（T1） scintillation and photodiode detector is used to measure the radiation intensity distribution of the MXR225/22 X-ray machine （made by Swiss COMET Inc.） along with various angles on different axis. At the same time, the radiation intensity distribution is simulated by Monte Carlo method. Results： The ＂broadening effect＂ is observed, and the boundary radiation intensity distribution broadening phenomena can be explained thereby. The radiation intensity distributions of the large and small focal are compared, and the reason for the difference in the cathode ends is analyzed. And the 2D radiation intensity distribution of X-ray machine is given. Conclusion： The results showed that in the 20° opening angle range （-10°-＋10°）, the radiation intensity distributes uniformly, the larger opening angle, the worse distribution uniformity. The radiation distribution extension occurs at the boundary of cathode side.