采用光纤和YAP晶体的小型γ相机的蒙特卡罗模拟

基于波长位移光纤(WSF)耦合YAP晶体中的光子传输特性，用GEANT4软件包建立了一个蒙特卡罗模拟程序.对采用波长位移光纤耦合平板式YAP晶体的小型单管γ相机的性能进行了计算机模拟.采用波长位移光纤耦合光电倍增管光阴极面的读出方式，和晶体直接耦合光电倍增管光阴极面相比，在相同的晶体面积大小条件下，PSPMT光阴极面积可大大缩小，使费用降低.模拟结果表明：γ射线与晶体发生作用的地方所对应的光纤输出的平均光子数最少为15个，位置灵敏光电倍增管完全可以探测到.说明采用闪烁晶体－WSF－位置灵敏光电倍增管的读出方式是可行的；在用硅油耦合波长位移光纤和YAP晶体的情况下，获得的空间分辨率为1.28 mm(FWHM).模拟结果也说明了增加平均光子数对提高空间分辨率的重要性.

Monte-Carlo Simulation of a Small Gamma Camera Using Fibers and YAP Scintillation Crystal

Based on the production and transportation of the fluorescence in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal,a simulation model has been setup using the GEANT4 codes for a small gamma camera with WSFs coupled to a YAP scintillation crystal. An advantage of this technique over direct readout with a position-sensitive photo-sensor is small amount of readout channel could be used for the same image area. Simulation results show that at least 15 photons on average for 59.5 keV gamma ray (241Am). A spatial resolution of 1.28 mm FWHM is obtained when silicone grease is used to couple to the fibers to the crystal. The factors affecting the number of photons and the spatial resolution are discussed.