Effect of monitor unit optimization on volumetric modulated arc therapy planning for nasopharyngeal carcinoma
10.19745/j.1003-8868.2025029
- VernacularTitle:机器跳数优化对鼻咽癌容积旋转调强放疗的影响研究
- Author:
Hua-qu ZENG
1
;
Hui ZHANG
;
Qi-bing WU
Author Information
1. 安徽医科大学生物医学工程学院,合肥 230032;高州市人民医院放疗中心,广东高州 525200
- Publication Type:Journal Article
- Keywords:
nasopharyngeal carcinoma;
volumetric modulated arc therapy;
monitor unit optimization;
monitor unit objective tool
- From:
Chinese Medical Equipment Journal
2025;46(2):56-62
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the effect of monitor unit(MU)optimization on volumetric modulated arc therapy(VMAT)for nasopharyngeal carcinoma(NPC).Methods Totally 21 NPC patients confirmed pathologically at some hospital from October 2022 to March 2023 were selected retrospectively,and for each patient a double-arc VMAT plan named base was designed without using the monitor unit objective(MUO)tool and optimized by the photon optimization algorithm.With the parameter kept constant,Plan base was reoptimized with only the MUO tool by regulating its Maximum MU to 30％of the total MU of Plan base and setting Strength values as 50,80 and 100 respectively to obtain Plan S50,S80 and S100.Plan base was compared with Plan S50,S80 and S100 in terms of dose distributions of the target volumes and organs at risk(OARs),MU,beam-on time and γ pass rate.SPSS 17.0 software was used for statistical analysis.Results In Plan S100 only 4 patients had a decrease of more than 4％in theD98％to the PCTV2 target volume compared with that in Plan base.In Plan S80 only 2 patients had a decrease of between 3％and 4％in the Dmax to PGTV and PGTVnd and D98％to PCTV2 when compared with those in Plan base,and most of the dosimetric parameters to the other target volumes had the changing amplitudes lower than 2％.When compared with Plan base,Plan S50,S80 and S100 all increased theDmaxto the brainstem significantly(all P＜0.05),with the maximum increment not exceeding 1.5％.In Plan S50 the D502％and Dmean to the right and left parotid glands were lowered,and in Plan S80 there were decreases found in the Dmean to the right and left parotid glands andD50％to the left parotid gland,with statistically significant differences(P＜0.001),and in Plan S100 the D50％and Dmean to the right and left parotid glands and the Dmax to the spinal cord increased significantly when compared with those in Plan base(all P＜0.05).In Plan S80 and S100 the V40 of the thyroid relatively rose statistically when compared with that in Plan base(P＜0.05).In Plan S50,S80 and S100 the MU was decreased by 5.1％,21.5％and 30.9％respectively when compared with that in Plan base,and the average beam-on time of all the four plans was kept within 2.5 min.γ pass rates increased sequentially for Plan base,S50,S80 and S100 under 1％/1 mm conditions.Conclusion In NPC VMAT MU optimization effectively decreases the planned MU and improves γ pass rates under 1％/1 mm conditions while ensuring the dose to the target volume and OAR protection.[Chinese Medical Equipment Journal,2025,46(2):56-62]
