Setup errors and margin expansion in radiotherapy for pediatric head and neck rhabdomyosarcoma
10.3969/j.issn.1005-202X.2025.10.001
- VernacularTitle:儿童头颈部横纹肌肉瘤放疗摆位误差分析及外放边界研究
- Author:
Yuanzi ZHA
1
;
Jun SU
1
;
Mawei JIANG
1
Author Information
1. 上海交通大学医学院附属新华医院放疗科,上海 200092
- Publication Type:Journal Article
- Keywords:
pediatric head and neck rhabdomyosarcoma;
radiotherapy;
setup error
- From:
Chinese Journal of Medical Physics
2025;42(10):1261-1265
- CountryChina
- Language:Chinese
-
Abstract:
Objective Radiotherapy plays a crucial role in the treatment of pediatric rhabdomyosarcoma.However,children face greater challenges than adults in maintaining precise body positioning during radiotherapy.This study aims to analyze and calculate the setup errors in children with head and neck rhabdomyosarcoma during radiotherapy,and determine the optimal clinical target volume-planning target volume(CTV-PTV)margin and organ-at-risk planning risk volume(OAR-PRV)margin.Methods A total of 102 pediatric patients with head and neck rhabdomyosarcoma who received radiotherapy using the Varian Edge linear accelerator were enrolled.All children were immobilized with a 5-point thermoplastic mold.During treatment,Varian cone-beam computed tomography(CBCT)images were acquired for setup verification in the first 3 fractions,followed by weekly CBCT verification thereafter.Setup errors were obtained in 6 directions:left-right(LR),superior-inferior(SI),anterior-posterior(AP),rotation around the X-axis(Pitch),rotation around the Y-axis(Roll),and rotation around the Z-axis(Rtn).Results A total of 791 CBCT images were acquired.The individual systematic errors in the LR,SI,and AP directions were 0.052,0.064,and 0.051 cm,respectively;the individual random errors in these 3 directions were 0.084,0.089,and 0.078 cm,respectively.According to the Stroom's formula in the ICRU-62 report,the calculated CTV-PTV margins in the LR,SI,and AP directions were 0.163,0.190,and 0.157 cm,respectively.Using the Van Herk formula,the CTV-PTV margins in the above 3 directions were 0.189,0.223,and 0.182 cm,respectively.The OAR-PRV margins calculated using the Mc Kenzie method were 0.110,0.128,and 0.105 cm in the LR,SI,and AP directions,respectively.Conclusion Based on the findings of this study,the CTV-PTV margins for pediatric head and neck rhabdomyosarcoma are within 0.3 cm,indicating that the 0.3 cm margin currently adopted by Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine is feasible.In addition,the OAR-PRV margins derived from this study are less than 0.2 cm,suggesting that the currently used 0.3 cm OAR-PRV margin can be reduced to 0.2 cm.This adjustment is beneficial for enhancing the protection of normal tissues while ensuring the treatment efficacy,thereby improving the accuracy and safety of radiotherapy.
