S A Pawiro, A Azzi, D S Soejoko
PhD, Department of Physics, Faculty of Mathematics and Natural Sciences, University of Indonesia, Depok, Indonesia.
MSc, Department of Physics, Faculty of Mathematics and Natural Sciences, University of Indonesia, Depok, Indonesia.
J Biomed Phys Eng. 2020 Oct 1;10(5):613-622. doi: 10.31661/jbpe.v0i0.1192. eCollection 2020 Oct.
Intensity Modulated Radiation Therapy (IMRT) technique is an advanced method of radiotherapy leading into the development of Flattening Filter-Free (FFF) medical linear accelerators (Linacs). Monte Carlo simulation has been a standard method for calculation of particle transport due to precise geometry and material specifications.
This study is to obtain the design optimization of Flattening Filter Free (FFF) for 6 MV Linac machine.
In this simulating study, EGSnrc user code was used to simulate particles emitted from head of linac 6MV Varian to achieve the most suitable filter in FFF linac design. Monte Carlo simulation results of the PDD and profile, on the 10 × 10 cm field, were compared with the measurements. Differences in small profile beams from Monte Carlo simulation were also evaluated between FF and FFF linac.
The spectrum on Monte Carlo simulation in isocenter was compared with Treatment Planning System (TPS) for each filter variation. The slight differences of average spectrum are simulated using 2 mm copper filter and with -1.52 ± 3.82% and -3.13 ± 3.61%. Whereas, for PDD and profiles, each variation has an average difference of 7.10 ± 0.70% and -5.99 ± 1.39%.
filter is a proper filter for the use of linac design 6MV Varian. It is necessary to decrease the kinetic energy of electrons to perform MC simulations on FFF linac.
调强放射治疗（IMRT）技术是一种先进的放射治疗方法，推动了无均整器（FFF）医用直线加速器（直线加速器）的发展。蒙特卡罗模拟由于精确的几何形状和材料规格，一直是计算粒子输运的标准方法。
本研究旨在获得6MV直线加速器无均整器（FFF）的设计优化。
在本模拟研究中，使用EGSnrc用户代码模拟Varian 6MV直线加速器头部发射的粒子，以实现FFF直线加速器设计中最合适的滤波器。将10×10 cm射野上的百分深度剂量（PDD）和剂量分布的蒙特卡罗模拟结果与测量结果进行比较。还评估了FF和FFF直线加速器在小射野光束上蒙特卡罗模拟的差异。
针对每个滤波器变化，将等中心处的蒙特卡罗模拟光谱与治疗计划系统（TPS）进行比较。使用2 mm铜滤波器模拟的平均光谱存在细微差异，分别为-1.52±3.82%和-3.13±3.61%。而对于PDD和剂量分布，每个变化的平均差异分别为7.10±0.70%和-5.99±1.39%。
该滤波器适用于Varian 6MV直线加速器设计。在FFF直线加速器上进行蒙特卡罗模拟时，有必要降低电子的动能。
