The application of two-dimensional ionization chamber array for relative dosimetric verification of intensity-modulated radiation therapy in nasoparyngeal carcinoma

Abstract

Objective Use two-dimensional ionization chamber array(matrixx)for relative dosimetry verification of intensity modulated radiation therapy(IMRT)nasoparyngeal carcinoma(NPC).Methods Thirty patients were treated with IMRT,used theirs IMRT plans transferred to verification of matrixx model,then generated quality assurance(QA)plane in therapy plan system (TPS).According to QA plan treat for twodimensional ionization chamber array with an actual gantry angle,and then output the measured plane dose distribution and identical plan dose distribution to ominiPro-IMRT software.Afterwards carry out QA plan and measured sectional image analysis,QA plan and measured isodose curve analysis by turns,and gamma analysis quantization.The gamma value[γ(rm)]of the measurement point,[γ(rm)]≤1 demonstrate point calculation passes,the passes point more than 90%indicate that QA plan passes for relative dosimetric verification.Results Thirty patients IMRT plans have twenty-seven plans calculation passes,the other three patients'passed point are 85.89%,86.56%,80.53%,which means the calculation fails.The pass rate is 90%.According to adjust therapy plan,theirs plan passed.Conclusion Two-dimensional ionization chamber array is easy and convenient to apply,which can be used as a tool for plane dose distribution verification of IMRT.It ensure that plan accuracy,which use a method of relative dosimetric verification for patients treated with intensity modulated radiation therapy. Key words: Radiotherapy planning,computer-assisted; Nasopharyhgeal neoplasms; Two-dimensional ionization chamber array; Relative dosimetrie verification