Papanikolaou N, Mackie T R, Meger-Wells C, Gehring M, Reckwerdt P
Department of Medical Physics, University of Wisconsin, Madison 53706.
Med Phys. 1993 Sep-Oct;20(5):1327-36. doi: 10.1118/1.597154.
The distribution of absolute dose per unit fluence from polyenergetic photon beams impinging upon a water phantom was calculated using two convolution approaches that properly account for beam hardening effects. Dose deposition kernels calculated previously using the EGS4 Monte Carlo code are convolved with the primary terma to give the dose for monoenergetic photon beams of energies ranging from 100 kev to 50 MeV. A polyenergetic dose distribution is composed of separately calculated monoenergetic components, which are appropriately weighted with the fluence spectrum to yield the polyenergetic dose distribution. Alternatively, a single convolution for the polyenergetic beam is considered, where a composite polyenergetic kernel is convolved with the respective polyenergetic terma. The effects of the polyenergetic kernel variance due to beam hardening as well as the effect of tilting the kernels for a diverging beam geometry were also examined. The depth dose data produced using the two proposed methods were compared with measured data and Monte Carlo simulations and showed good agreement.
使用两种能适当考虑射束硬化效应的卷积方法，计算了多能光子束撞击水模体时每单位注量的绝对剂量分布。先前使用EGS4蒙特卡罗代码计算的剂量沉积核与初级项进行卷积，以给出能量范围从100千电子伏到50兆电子伏的单能光子束的剂量。多能剂量分布由单独计算的单能分量组成，这些分量用注量谱进行适当加权，以产生多能剂量分布。或者，考虑对多能束进行单次卷积，其中复合多能核对各自的多能初级项进行卷积。还研究了由于射束硬化导致的多能核方差的影响以及对于发散束几何形状使核对倾侧的影响。使用这两种提议方法产生的深度剂量数据与测量数据和蒙特卡罗模拟进行了比较，结果显示吻合良好。
