Abstract：Objective To study the dosimetric differences of volume modulated arc therapy (VMAT) plans for nasopharyngeal
carcinoma in different beam mode of linear accelerator, and to provide reference for the selection of the best beam mode in
nasopharyngeal carcinoma VMAT radiotherapy. Methods A total of 10 patients with nasopharyngeal carcinoma admitted to our
hospital were selected to design 6 X VMAT plan under 6 MV X-ray flattening filter (FF) mode, 6 FFF VMAT plan under 6 MV
X-ray flattening filter free (FFF) mode and 10 X VMAT plan under 10 MV X-ray FF mode with the same prescription dose and plan
parameters. The dosimetric characteristics of the three plans were compared. Results The three plans had little difference in target
dose and could meet the prescription dose requirement. The 6 FFF VMAT plan was slightly inferior to the 6X VMAT plan and 10X
VMAT plan in a few evaluation indicators, and on the Dmean of PTV5115, the 6 FFF VMAT plan was higher than the 6X VMAT plan
and 10X VMAT plan; On the Dmean and D2% of PTV6417, the 6 FFF VMAT plan was higher than the 6X VMAT plan. At D98% of PTV6603,
the 6 FFF VMAT plan was lower than the 6X VMAT plan. On the Dmean of PTV6975, the 6FFF VMAT plan was higher than the 6X
VMAT plan, the differences were statistically significant (P<0.05). Compared with other target dose indicators and target coverage,
there was no significant difference among the three plans (P>0.05). The advantages in the protection of endangered organs were ranked as 6
FFF VMAT plan >10X VMAT plan >6X VMAT plan. 6 FFF VMAT plan had certain advantages over 10X VMAT plan and 6X VMAT
plan in protecting skin and normal tissue, and 10X VMAT plan was superior to 6X VMAT plan. The monitor units in 6 FFF VMAT
plan and 10X VMAT plan was significantly higher than that in 6X VMAT plan (P<0.05). Conclusion The VMAT plan of 6X, 6 FFF
and 10X can meet the clinical requirements and have their own characteristics. Compared with 10X VMAT and 6X VMAT plan, the
6 FFF VMAT plan has more advantages in the protection of endangered organs and normal tissues. Compared with 6X VMAT plans,
10X VMAT plans have the same or even better level in the protection of target areas and organs. From the point of view of planning
optimization, the VMAT plan under 6 FFF is recommended to reduce the dose of exposure to organs at risk.
谭军文，龙雨松，贺先桃，李钢，冯永富，梁卫学，王占宇. 直线加速器不同出束模式对鼻咽癌
容积旋转调强放疗计划的影响[J]. 中国医疗设备, 2023, 38(10): 56-61.
TAN Junwen, LONG Yusong , HE Xiantao, LI Gang, FENG Yongfu, LIANG Weixue, WANG Zhanyu. Effect of Different Beam Mode of Linear Accelerator on VMAT Plans for Radiotherapy of
Nasopharyngeal Carcinoma. China Medical Devices, 2023, 38(10): 56-61.
