中文摘要：

提出一种基于MonteCarlo模拟的快速有限笔柬算法（finite size pencil beams，FSPB），并根据有限笔束的核心思想，利用MonteCarlo模拟的多角度1cm×1cm野剂量分布数据，对不同入射角度的有限笔束的剂量分布数据进行直接矩阵存储，完全束的剂量分布基于原始数据的叠加得到．基于若干算例，比较分析了本算法计算结果与MonteCarlo直接模拟的实际剂量分布，其精度和速度达到预期效果．本算法为IMRT逆向计划过程的剂量计算又增加了一种算法选择．

英文摘要：

A fast finite size pencil beam algorithm based on Monte Carlo simulation is presented. The dose distribution of a series of finite size pencil beams with different incident angles simulated by Monte Carlo code was directly stored as matrix. The full beam dose distribution would be obtained by direct superposition. Some regular and irregular fields were calculated by this algorithm and verified by Monte Carlo simulation. Results show that the proposed algorithm can satisfy the requirement of accuracy and speed for IMRT TPS, which provides a new choice for dose calculations.