闪烁体衰减常数对辐射源边界测量影响数值模拟
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摘要
在辐射成像系统测量辐射源边界中,有闪烁体时间弥散效应得到的边界值与没有闪烁体时的真实边界值存在差别,影响辐射源尺寸变化计算。研究构建了一类辐射源强时间宽度、半径扩散速率与边界相对强度不同的辐射源,应用卷积和图像强度梯度法,对选用BC408,LaBr3和LSO闪烁体得到的边界与真实边界的偏差进行了数值模拟计算。结果表明,拍摄时间为20ns时,由BC408闪烁体得到的边界值偏差最小;若偏差小于1mm认为闪烁体适合测量,BC408,LaBr3和LSO测量的强度时间宽度最小值分别为33ns,133ns和266ns;拍摄全积分图像时偏差大小不受闪烁体不同的影响;最终得出的偏差计算公式较好地反映了真实偏差的变化趋势。
In the measurement of radiation source boundary using radiation imaging system,time diffusion of scintillant affects the measurement result.We constructed a type of radiation source having different intensity time width,boundary diffusion speed and relative intensity,then computed the deviation betweens boundary real size with the sizes in cases of scintillants BC408,LaBr3 and LSO respectively,by means of convolution and image intensity gradient.The results show that while photography time is 20 ns,deviation will be the smallest with the scintillant BC408;since a scintillator is not suitable for the measurement when deviation is greater than 1mm,the minimum values of intensity time width should be 266 ns,133ns and 33 ns for scintillants LSO,LaBr3 and BC408,respectively;however,the deviation doesn′t vary with scintillant materials in complete integral imaging.Finally,a formula is summed up for deviation computation,which can well reflect the trend of real deviation.
In the measurement of radiation source boundary using radiation imaging system,time diffusion of scintillant affects the measurement result.We constructed a type of radiation source having different intensity time width,boundary diffusion speed and relative intensity,then computed the deviation betweens boundary real size with the sizes in cases of scintillants BC408,LaBr3 and LSO respectively,by means of convolution and image intensity gradient.The results show that while photography time is 20 ns,deviation will be the smallest with the scintillant BC408;since a scintillator is not suitable for the measurement when deviation is greater than 1mm,the minimum values of intensity time width should be 266 ns,133ns and 33 ns for scintillants LSO,LaBr3 and BC408,respectively;however,the deviation doesn′t vary with scintillant materials in complete integral imaging.Finally,a formula is summed up for deviation computation,which can well reflect the trend of real deviation.
引文
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[4]Guo Jinchuan,Zhou Bin,Liu Xin,et al.Large format X-ray image detector of high resolution and sensitivity[C]//Proc of SPIE.2010:78452M.
[5]胡孟春,刘建,李忠宝,等.国产LaCl3无机闪烁体对14MeV中子的伽马中子灵敏度比测量[J].仪器仪表学报,2011,32(12):174-177.(Hu Mengchun,Liu Jian,Li Zhongbao,et al.Measurements of sensitivities relation between gamma-ray and the 14 MeV-neutron for Homemade LaCl3:Ce Inorganic Scintillator.Chinese Journal of Scientific Instrucment,2011,32(12):174-177)
[6]唐世彪,马庆力,阴泽杰.快中子成像空间分辨率部分影响因素的模拟研究[J].核电子学与探测技术,2015,35(2):206-214.(Tang Shibiao,Ma Qingli,Yin Zejie.A simulation study of influencing factor of spatial resolution in fast neutron imaging.Nuclear Electronics&Detection Technology,2015,35(2):206-214)
[7]Nassalski A,Moszynski M,Syntfeld A,et al.Non-proportionality of organic scintillators and BGO[J].IEEE Trans Nuclear Science,2008,55(3):1069-1072.
[8]刘兆庆.脉冲辐射场诊断技术[M].北京:科学出版社,1994.(Liu Zhaoqing.Pulse radiation field diagnostic technique.Beijing:Science Press,1994)
[9]Yin Jianjun,Zhang Jianqiu,Zhuang Zesen.The Gaussian sum convolution probability hypothesis density filter[C]//9th International Conference on Signal Processing.2008.
[10]于天虎,毛兴鹏,王国谦,等.一种基于灰度的梯度边界检测优化算法[J].计算机应用研究,2010,27(1):361-364.(Yu Tianhu,Mao Xingpeng,Wang Guoqian,et al.Optimal algorithm for gradient based on edge detection.Application Research of Computers,2010,27(1):361-364)