Rogers D W, Bielajew A F
Med Phys. 1985 Nov-Dec;12(6):738-44. doi: 10.1118/1.595657.
This report investigates the buildup region of the depth-dose curve for broad parallel beams of 60Co and lower energy photons incident on slabs of tissue as defined by the International Commission on Radiation Units and Measurements (ICRU) and other materials. The EGS Monte Carlo system was used to simulate the transport of photons and electrons in the materials. Calculated buildup regions of the depth-dose curves are presented for photons incident on ICRU tissue. For 60Co beams, the primary and scatter dose components are presented, both for the buildup region and at depth in the phantom. Effects of beam radius were investigated and found to have only a small effect in the buildup region of the central axis depth-dose curve. The calculated effects of beam radius are larger at depth and in good agreement with experiment. Effects of scatter and attenuation in a small miniphantom of water were investigated as a function of photon energy and were found to cancel within 0.8%. The mean distance of electron transport was calculated for 60Co beams incident on carbon, water, polystyrene, aluminum, and lead.
本报告研究了如国际辐射单位与测量委员会（ICRU）所定义的，60Co宽平行束和较低能量光子入射到组织平板及其他材料上时深度剂量曲线的积累区。使用EGS蒙特卡罗系统模拟光子和电子在材料中的传输。给出了光子入射到ICRU组织上时计算得到的深度剂量曲线的积累区。对于60Co束，给出了积累区和模体深度处的原发射线剂量分量和散射剂量分量。研究了射束半径的影响，发现其对中心轴深度剂量曲线的积累区只有很小的影响。计算得到的射束半径影响在深度处更大，且与实验结果吻合良好。研究了小水模体中散射和衰减随光子能量的变化，发现其相互抵消在0.8%以内。计算了60Co束入射到碳、水、聚苯乙烯、铝和铅上时电子传输的平均距离。
