Influences of various field-defining methods of Varian accelerator on radiation dosimetry parameters
10.3760/cma.j.issn.0254-5098.2017.09.014
- VernacularTitle:Varian加速器不同的射野形成方式对射野剂量学参数的影响
- Author:
Yaqin ZHENG
1
;
Tong CUI
;
Xuliang ZHENG
;
Jianting LIU
;
Xiaofen XING
Author Information
1. 山西省肿瘤医院 山西医科大学附属肿瘤医院放射治疗中心
- Keywords:
Field defining method;
Intensity modulated radiotherapy;
Dosimetry
- From:
Chinese Journal of Radiological Medicine and Protection
2017;37(9):709-712
- CountryChina
- Language:Chinese
-
Abstract:
Objective To evaluate the influences of various field-defining method of Varian accelerator on radiation dosimetry parameters, and provide theoretical basis for the beam modeling of the treatment planning system ( TPS ) . Methods The percentage depth dose ( PDD ) , the off-axis ratio ( OAR ) and the total scattering factors ( Scp ) of radiation fields were measured in three different conditions, including collimators (JAW), multileaf collimator(MLC) and JAW +MLC. The measured data was analyzed and compared with each other. Results The PDD of central axis was marginally influenced by three field-defining method. In both directions, the MLC-defined field sizes were larger by a maximum of 2. 9 mm ( left-right) or 1. 7 mm ( gun-target) than the JAW-defined ones. In the left-right direction, the width of field penumbra shaped by MLC was larger than the field of the same size as defined by JAW. The result of gun-target direction was to the contrary. In both directions, the field penumbra and size displayed no significant differences as defined by JAW+MLC or JAW. Conclusions The field size, penumbra width, and the total scattering factors were influenced by field-defining method, which indicates that special attention should be paid to the dosimetric parameters of MLC during TPS beam modeling for IMRT planning.
