Research on the application of 2-D air vented ionization chamber array MatriXX system
10.3760/cma.j.issn.0254-5098.2009.01.031
- VernacularTitle:二维空气电离室矩阵MatriXX系统的应用研究
- Author:
Shuxu ZHANG
;
Linghong ZHOU
;
Guangjie CHEN
;
Shengqu LIN
;
Guohui SHEN
;
Yufeng WANG
- Publication Type:Journal Article
- Keywords:
2D air vented ionization chambers array;
MatriXX;
2-D dose distribution verification;
Phantom
- From:
Chinese Journal of Radiological Medicine and Protection
2009;29(1):93-96
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the features of 2-D air vented ionization chamber array MatriXX system to use the QA procedures of radiotherapy. Methods Some important QA procedure of clinical radiotherapy practice were investigated by using a MatriXX system and a phantom made in house, mainly including the calibration of MatriXX, the off-axis rate (OAR) of virtual wedge fields, the connection between two half-fields or two asymmetry-fields, the skillful adjustment of the clinac flat filter, the 2-D dose distribution verification of radiotherapy planning, the influence of scatter screen to a large area electron beam field, the effect and best thickness and shielding position of block for a large area electron beam fields with scatter screen. Results The OAR of any virtual wedge field can be measured by a MatriXX system in a single irradiation. The conjunction accuracy of two half-fields or two asymmetry-fields may be less than 1 ram. The difference between the calculated and measured dose of any point or any isodose or any OAR of a field can be determined by using a MatriXX system. After the adjustment of the elinae flat filter with the help of MatriXX system, the flatness and symmetry of the field are 1. 85 % and 0.98 %, respectively. The dose characteristic of a large area electron beam field may be distinctively influenced by a scatter screen, and under this condition, the block faraway from the shielded target can hardly protect the organ at risk, and directe block which is put on or near the organ at risk is perfect. Conclusion Compared with conventional ionization chamber (Farmer type) or film dose measuring, the MatriXX combined with the OmniPre I'mRT software is much more convenient and effective in QA practice of clinical radiotherapy, and it's a perfect tool for the QA procedure of radiation therapy.
