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| Correction of Angular Dependence of MatriXX Ion Chambers for IMRT Plan Verification |
| KONG Yan, KONG Dong, WEI Xian-ding, CUI Qiang-liang, YANG Bo |
| Department of Radiation Oncology, Affiliated Hospital of Jiangnan University Wuxi 4th People's Hospital, Wuxi 214062 China |
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Abstract Objective Angular dependence of MatriXX is a problem when used in composite dose verification of IMRT,and this work aimed at correcting angular dependence of each unit ion chamber(UIC) in MatriXX array respectively.Methods At 0° gantry angle with open field 28cm×28cm,plane dose distribution was measured by MatriXX,and then compared to the calculated value from treatment planning system(TPS),so that dose calibration coefficients of each UIC were obtained.Based on this,dose distributions under different gantry angles and open field were also measured,and corrected by the corresponding calculated value for each UIC at each gantry angle.Then,dose distributions from actual IMRT plan fields were measured,and plan verification Results with angular dependence correction or not were both obtained and compared,in order to evaluate this correction method.Results At 0° gantry angle,the dose calibration coefficients of each UIC lightly increased with their X,Y values increasing,and were averaged to be 1.00 ±0.01. For 60°~150° and 210°~300° gantry angle ranges,the angular dependence coefficients had large range and fluctuation,and around 90° and 270°,the coefficients reached the smallest. Verification results after correction were better than those without.Conclusion After this angular dependence correction,MatriXX could be more suitably used for actual IMRT plan with different gantry angles.
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Received: 05 January 2016
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