Papatheodorou S, Zefkili S, Rosenwald J C
Institut Curie, Service de Physique Médicale, Paris, France.
Phys Med Biol. 1999 Feb;44(2):509-24. doi: 10.1088/0031-9155/44/2/016.
The purpose of this work was to establish procedures for the implementation of the Varian Enhanced Dynamic Wedge into a treatment planning system (TPS), based as much as possible on simple theoretical considerations and already available data. A method is presented for the calculation (rather than measurement) of off-axis relative wedge transmission curves that are required by the TPS for relative dose calculations. We also present a method for absolute dose (monitor unit) calculations, based on the calculation of an effective wedge factor on the prescription point. A simple formula has been derived for the calculation of the effective wedge factor for the most general case, i.e. an arbitrary effective wedge angle, field size and prescription point. Relative dose calculations have been verified by measurements performed on a Varian Clinac 2300C/D linear accelerator, for 6 MV and 20 MV photon energies. Monitor unit calculations have also been verified experimentally for several cases such as symmetric and asymmetric fields with prescription on the collimator axis or on the geometrical centre of the asymmetric field. The presented technique provides results within 2% for both relative and absolute dose calculations for clinically relevant cases.
这项工作的目的是尽可能基于简单的理论考量和已有数据，建立将瓦里安增强动态楔形板纳入治疗计划系统（TPS）的程序。本文提出了一种用于计算（而非测量）TPS进行相对剂量计算所需的离轴相对楔形板传输曲线的方法。我们还提出了一种基于处方点有效楔形因子计算的绝对剂量（监测单位）计算方法。针对最一般的情况，即任意有效楔形角、射野大小和处方点，推导了一个用于计算有效楔形因子的简单公式。通过在瓦里安Clinac 2300C/D直线加速器上对6 MV和20 MV光子能量进行的测量，验证了相对剂量计算结果。对于诸如在准直器轴上或非对称射野几何中心处有处方的对称和非对称射野等几种情况，也通过实验验证了监测单位计算结果。对于临床相关病例，所提出的技术在相对剂量和绝对剂量计算中均能提供2%以内的结果。
