The effect of environmental radiation of radiotherapy workplace on stereotactic radiation therapy plan dose verification using an Exradin W1 scintillator detector
10.3760/cma.j.issn.0254-5098.2021.05.009
- VernacularTitle:放疗工作环境辐射对Exradin W1闪烁体探测器测量立体定向治疗计划的影响
- Author:
Zike HUANG
1
;
Cui YANG
;
Jiazhou WANG
;
Weigang HU
;
Xu HAN
Author Information
1. 复旦大学附属肿瘤医院放射治疗中心 复旦大学上海医学院肿瘤系，上海 200032
- Keywords:
Plastic scintillator detector;
Dose verification;
Stereotactic radiation therapy plans;
Quality assurance
- From:
Chinese Journal of Radiological Medicine and Protection
2021;41(5):368-373
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To study the influence of environmental radiation of radiotherapy workplace on the stereotactic radiation therapy(SRT) plan absolute dose verification with plastic scintillator detector Exradin W1.Methods:The computed tomography (CT) image of the stereotactic dose verification phantom (SDVP) was scanned and imported into the treatment planning system. Three schemes, including 3 cm × 3 cm to 20 cm × 20 cm square gradient field irradiation, virtual planning target volume(PTV) non-coplanar arcs irradiation and 10 cases of volumetric modulated arc radiotherapy SRT (VMAT SRT) clinical plan verification, were measured with or without a home-made shield over the photodiode. Measurements were recorded to analyze the impact of environmental radiation on dose measurement under different conditions.Results:The noise effect of the photodiode increased with the the lager open field size, and decreased with the reduced distance between the photodiode and isocenter. The contribution of photodiode noise effect increase with the lager non-coplanar arc field size, with the largest up to 4.16%. As for the clinical SRT plan verification measurement, the relative difference between the SRT plan measurements and treatment planning system(TPS) before and after shielding were (1.39±1.05)% and (0.59±1.03)%, respectively ( t=-5.343, P < 0.05). and for W1 vs. A16 microchamber was (1.22±1.56)% and (0.42±1.42)%, respectively ( t=-5.414, P < 0.05). Conclusions:The measurements of Exradin W1 are in good agreement with the TPS result and the ionization chamber measurements, but its accuracy is easily affected by the environmental radiation of radiotherapy workplace. To measure non-coplanar radiation, the photodiode should be placed as far away as possible from the isocenter and be properly shielded, which can effectively improve the accuracy and stability of the measurement and provide a strong guarantee for clinical precision radiotherapy.
