|Table of Contents|

Effect of MLC systematic error on planned dose distribution of VMAT in cervical cancer of different complexity

Journal Of Modern Oncology[ISSN:1672-4992/CN:61-1415/R]

Issue:
2023 23
Page:
4394-4399
Research Field:
Publishing date:

Info

Title:
Effect of MLC systematic error on planned dose distribution of VMAT in cervical cancer of different complexity
Author(s):
FAN Peng1; WANG Xunyu1; PENG Qinghe2; FENG Zhengfu1; LYU Zhenhua1; GUO Wanjin1; WANG Xin1
1.Department of Radiation Oncology,The Sixth Affiliated Hospital of Guangzhou Medical University,Qingyuan People's Hospital,Guangdong Qingyuan 511518,China;2.Department of Radiation Oncology,Sun Yat-sen University Cancer Center,State Key Laboratory of Oncology in South China,Collaborative Innovation Center for Cancer Medicine,Guangdong Guangzhou 510060,China.
Keywords:
cervical cancer; VMAT; MLC; systematic error; plan complexity
PACS:
R737.33
DOI:
10.3969/j.issn.1672-4992.2023.23.018
Abstract:
Objective:To study the effect of multi-leaf collimator(MLC) systematic error on the dose of cervical cancer VMAT planning,and quantitatively analyze the correlation between planning complexity and target dose variation.Methods:A retrospective selection was perfored in 14 cases of cervical cancer VMAT plan.The simulation plan was formed by artificially introducing the shifts error(Type 1),the single-sided shifts error(Type 2),and bilateral reverse shifts error(Type 3) for each planned MLC in Python,and the dosimetric differences between the original plan and the simulation plan were compared.The plan complexity was measured by the small aperture score(SAS),and the correlation between the complexity and the amount of dose change in the target area was analyzed by linear regression.Results:When the MLC error was 2 mm,Type 1 has little effect on planned dosimetry,error results in a <2% change in dose parameters.Type 3 had the most obvious effect on dose,with changes of PTV D95%,Dmean,Dmax and gEUD of 5.31%,5.52%,9.37% and 5.48%,respectively.The Dmean changes in the small intestine,rectum,femoral head and bladder were 7.96%,6.68%,8.85% and 7.41%,respectively.Type 2 had almost half the impact of Type 3.In addition,when the MLC error type was Type 2,Type 3,the mean dose deviation between the target and the organ at rise Dmean was strongly and linearly correlated with SAS(5 cm)(R2≥0.63).Conclusion:Type 2 and Type 3 MLC leaf systematic errors have a significant effect on the planned dose parameters.In order to ensure that the MLC systematic error leads to a <2% change in the target dose,during quality control,the overall error of MLC leafs should be less than 0.4 mm on each side or 0.9 mm on one side,and the SAS value can be used as an evaluation index to estimate

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Last Update: 2023-10-31