A Study of Dose Evaluation for Clinac and Treatment Planning System Based on 2D Ionization Chambers Array
10.3969/j.issn.1005-202X.2010.02.001
- VernacularTitle:利用矩阵电离室对加速器和放疗计划系统进行剂量学研究
- Author:
Jun LIU
;
Hong CHEN
;
Xiang PAN
;
Li ZHANG
;
Yonggang WANG
- Publication Type:Journal Article
- Keywords:
linear accelerator,treatment planning system;
verification;
intensity modulated radiotherapy (IMRT)
- From:
Chinese Journal of Medical Physics
2010;27(2):1699-1703
- CountryChina
- Language:Chinese
-
Abstract:
Objective: To discuss the methods and items for clinical linear accelerator (Clinac) and 3D treatment planning system (TPS)/intensity modulated radiotherapy(IMRT) system based on 2D ionization chambers array(2D-ICA). Methods: The 2D-I-CA laid on the anthropomorphic phantom with five centimeters and which was put on another five centimeters same phantom.All data have gained as following conditions: the SAD is 100 cm and the SSD is 90 cm; the fields' size are 2 cm, 5 cm, 10 cm,15 cm ,20 cm respectively and 2 cm×10 cm ,5 cm×20 cm ,20 cm×5 cm, MU=100 cGy;the Clinae and TPS were verified by some special items for checking their dose accuracy, such as, square fields, rectangular fields, and rectangular fields with 600 wedge or 300 wedge, which were measured for verification their flatness and symmetry. And some measured items were only for checking multileaf collimator (MLC) and TPS calculated accuracy. So, we developed moveable MLC fields and IMRT plans and compound fields to evaluate leafs side effects and leafs end effects and transmission effects. Results: The flatness value of square and rectangular fields was 100.07%～102.66%,and their symmetry value was 0.10%～1.49%; and these irradiate fields' size were compared with light fields' sizes, which the X direction deviation was-1.5%～0.7% ,the Y direction deviation was-1.4%～1.0%,and their average value was-0.47%.To verify calculated data for TPS ,we developed Gamma value and ab-solute value (<4%)to evaluate their accuracy. For square and rect-angular fields, The Gamma value was 92.02%～96.35%.In com-pound fields Which were composed with two half fields (X1 = 5 cm, X2 =0 cm, Y= 10 cm and X1 = 0 cm,X2 = 5 cm, Y=10 cm),the maximum deviation was about 5%.And five fields (2 cm×10 cm) composed one fields (10 cm×10 cm),the maximum deviation was about 10% in the joint place. The Gamma value of one fields was 96.6%, another was 93.2% in the moveable fields. Conclusions: To dollop 2D ionization chambers array to verify the dose for Clinac and TPS, it was so quick and simple, and it was important that it bring more accurate dose evaluation and more clinical quality assurance and quality control methods.
