分析LSO无机闪烁晶体中荧光弥散的原理。采用蒙特卡罗方法，将荧光弥散分为γ光子在LSO闪烁体中转化为次级电子并沉积能量，以及沉积能量转换为荧光光子在闪烁体中输运2个过程进行模拟。其中，前一过程采用MCNP蒙特卡罗程序模拟，后一过程的模拟计算由自编蒙特卡罗程序实现。给出了闪烁体的点扩散函数，计算结果与刀口法实验测量得到的点扩散函数相吻合。采用该方法计算了不同入射γ射线能量和各种厚度闪烁体下的点扩散函数。数据结果表明：点扩散函数的FWTM(full width at tenth maximum)随着γ射线能量的增大先减后增，并逐渐趋于稳定，还随着闪烁体厚度的增加而逐渐增大，文中给出了呈现这种变化规律的原因。

Fluorescence dispersion of Lu2SiO5 crystal as a γ-image converter was analyzed in theory and point spread function (PSF) of LSO scintillator was studied using Monte Carlo method. The simulation was divided into two processes. The energy deposition distribution of γ-ray was calculated with MCNP code and transferred to distribution of light photons in the scintillator. PSF was obtained through the Monte Carlo simulation of light transport, which was not available by MCNP code. The result was verified by PSF measurement in the knife-edge experiment. The FWTM (full width at tenth maximum) of PSF, which indicates spatial resolution, was calculated as a function of incident γ-ray energy and LSO thickness.