Radiation Oncology Department Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Phys Med Biol. 2011 May 21;56(10):3073-89. doi: 10.1088/0031-9155/56/10/012. Epub 2011 Apr 20.
The Monte Carlo method enables accurate dose calculation for radiation therapy treatment planning and has been implemented in some commercial treatment planning systems. Unlike conventional dose calculation algorithms that provide patient dose information in terms of dose to water with variable electron density, the Monte Carlo method calculates the energy deposition in different media and expresses dose to a medium. This paper discusses the differences in dose calculated using water with different electron densities and that calculated for different biological media and the clinical issues on dose specification including dose prescription and plan evaluation using dose to water and dose to medium. We will demonstrate that conventional photon dose calculation algorithms compute doses similar to those simulated by Monte Carlo using water with different electron densities, which are close (<4% differences) to doses to media but significantly different (up to 11%) from doses to water converted from doses to media following American Association of Physicists in Medicine (AAPM) Task Group 105 recommendations. Our results suggest that for consistency with previous radiation therapy experience Monte Carlo photon algorithms report dose to medium for radiotherapy dose prescription, treatment plan evaluation and treatment outcome analysis.
蒙特卡罗方法能够实现放射治疗计划的精确剂量计算，并且已经在一些商业治疗计划系统中得到了应用。与传统的剂量计算算法不同，传统的剂量计算算法以可变电子密度的水剂量形式提供患者剂量信息，而蒙特卡罗方法则计算不同介质中的能量沉积，并以介质剂量表示。本文讨论了使用不同电子密度的水计算的剂量与为不同生物介质计算的剂量之间的差异，以及剂量规范方面的临床问题，包括用水剂量和介质剂量进行剂量规定和计划评估。我们将证明，传统的光子剂量计算算法使用不同电子密度的水计算出的剂量与蒙特卡罗模拟的剂量相似，这些剂量与介质剂量接近（<4%的差异），但与根据美国医学物理学家协会（AAPM）第 105 工作组建议从介质剂量转换而来的水剂量差异显著（高达 11%）。我们的结果表明，为了与以前的放射治疗经验保持一致，蒙特卡罗光子算法应报告介质剂量，用于放射治疗剂量规定、治疗计划评估和治疗结果分析。
