Poolnapol Vanida, Sanghangthum Taweap, Keawsamur Mintra
Medical Physics Program, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Division of Radiation Oncology, Department of Radiology, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand.
J Med Phys. 2022 Jan-Mar;47(1):20-26. doi: 10.4103/jmp.jmp_63_21. Epub 2022 Mar 31.
Interplay effects have become the significant problem in lung cancer radiotherapy. Since these effects yield dose variation within the target and surrounding tissues.
The aim of this study is to investigate the effect of the dosimetric parameters of interplay effects in 6 MV flattening filter-free (FFF) photon beams for lung cancer.
This study performed planning, measurement, and data analysis sections for examining different breathing amplitudes and phases, doses, dose rates, field sizes, and fractionations.
Standard and clinical plans were created on the eclipse treatment planning system. The static and dynamic measurements were performed using a robotic platform and two-dimensional (2D) diode array. The gamma passing rates were defined as the percent of dose variation caused by the interplay effects.
Unpaired -test.
The outcomes showed three trends between gamma passing rates (γ) and dosimetric parameters. First, a decreasing trend was breathing amplitudes. The lowest γ of maximum amplitudes (2 cm) in both one dimensional and 2D were <25%. Second, an increasing trend was field sizes. The lowest γ of minimum field size (4 cm × 4 cm) was <55%. Third, constant outcomes were breathing phases, doses, dose rates, and a number of fractions. The γ values of these factors were 53.1%, 55.1%, 34.7%, and 36.7%, respectively.
Lung tumor motion-induced interplay effects in 6 MV FFF photon beams are more pronounced for higher breathing amplitudes and smaller field sizes.
相互作用效应已成为肺癌放射治疗中的重大问题。因为这些效应会导致靶区及周围组织内的剂量变化。
本研究旨在探讨6兆伏无均整器（FFF）光子束中相互作用效应的剂量学参数的影响。
本研究进行了计划、测量和数据分析部分，以检查不同的呼吸幅度和相位、剂量、剂量率、射野大小和分割次数。
在Eclipse治疗计划系统上创建标准和临床计划。使用机器人平台和二维（2D）二极管阵列进行静态和动态测量。伽马通过率定义为相互作用效应引起的剂量变化百分比。
非配对t检验。
结果显示伽马通过率（γ）与剂量学参数之间存在三种趋势。第一，呼吸幅度呈下降趋势。一维和二维中最大幅度（2厘米）时的最低γ均<25%。第二，射野大小呈上升趋势。最小射野大小（4厘米×4厘米）时的最低γ<55%。第三，呼吸相位、剂量、剂量率和分割次数的结果保持不变。这些因素的γ值分别为53.1%、55.1%、34.7%和36.7%。
在6兆伏FFF光子束中，肺部肿瘤运动引起的相互作用效应在呼吸幅度较高和射野较小的情况下更为明显。
