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应用ＥＧＳ４ Ｍｏｎｔｅ Ｃａｒｌｏ程序模拟了单源情况下，~（６０）Ｃｏ γ射线经Ｌｅｋｓｅｌｌ Ｇａｍｍａ Ｕｎｉｔ准直系统后直射（未经散射）光子和散射光子在终准直器外平面上的半径分布、能量分布及角度分布。模拟结果表明，在终准直器的外孔径范围内，直射光子数目约比散射光子数目高２－３个数量级，而在准直器孔径外，散射光子的份额不可忽略。对于光子的散射，又以康普顿散射为主，其它散射所占的份额很小，并且在准直器孔径内主要的是一次散射。
The EGS4 Monte Carlo program is used to simulate the radius distribution of direct (un-scattered) photons and scattered photons on the outer plane of the final collimator after a ~ (60) Co γ-ray passes through a Leksell Gamma Unit collimation system. Distribution and angle distribution. The simulation results show that the number of direct photons is about 2-3 orders of magnitude higher than the number of scattered photons within the outer diameter of the final collimator, and the fraction of scattered photons outside the collimator aperture can not be neglected. For photon scattering, Compton scattering again, the share of other scattering is small, and in the collimator aperture is the primary scattering.