Int J Radiat Oncol Biol Phys. 1991 May 15;21(1):25-36. doi: 10.1016/0360-3016(91)90165-z.
We discuss geometric and physical aspects of dose calculational methodologies as developed and implemented in three-dimensional treatment planning systems at four institutions participating in an NCI Contract for the Evaluation of High Energy Photon External Beam Treatment Planning. The geometric aspects include such issues as unconventional beam orientations, 3-D patient geometry, image data requirements, and pathlength calculation in 3-D. The physical aspects deal primarily with the formalisms employed in dose calculations. Exact calculation of dose is impractical due to the complex manner in which radiation interacts with matter. Approximations have to be made which limit the accuracy of dose calculations. For a number of situations of clinical interest, especially for regions where electronic equilibrium does not exist, the accuracy of conventional methods of dose calculations is suspect. New, more accurate methods have been proposed but have not been implemented to date. Three-dimensional dose calculations are very time consuming with currently available general purpose computers. With the development of the next generation of computers and other ancillary hardware and with continuously evolving algorithms, accurate and fast three-dimensional dose calculations should become affordable for the radiotherapy community in the near future.
我们讨论了参与美国国立癌症研究所（NCI）高能光子外照射治疗计划评估合同的四家机构在三维治疗计划系统中开发和实施的剂量计算方法的几何和物理方面。几何方面包括非常规射束方向、三维患者几何形状、图像数据要求以及三维路径长度计算等问题。物理方面主要涉及剂量计算中使用的形式体系。由于辐射与物质相互作用的方式复杂，精确计算剂量是不切实际的。必须进行近似处理，这限制了剂量计算的准确性。对于许多具有临床意义的情况，特别是对于不存在电子平衡的区域，传统剂量计算方法的准确性令人怀疑。已经提出了更新、更准确的方法，但迄今为止尚未实施。使用当前可用的通用计算机进行三维剂量计算非常耗时。随着下一代计算机和其他辅助硬件的发展以及算法的不断演进，在不久的将来，精确且快速的三维剂量计算对于放射治疗界来说应该会变得经济可行。
