Son Jaeman, Baek Taesung, Lee Boram, Shin Dongho, Park Sung Yong, Park Jeonghoon, Lim Young Kyung, Lee Se Byeong, Kim Jooyoung, Yoon Myonggeun
Department of Bio-Convergence Engineering, Korea University, Seoul, Korea ; Proton Therapy Center, National Cancer Center, Goyang, Korea.
Department of Bio-Convergence Engineering, Korea University, Seoul, Korea ; Department of Radiation Oncology, Ilsan Hospital, Goyang, Korea.
Radiol Oncol. 2015 Aug 21;49(3):307-13. doi: 10.1515/raon-2015-0021. eCollection 2015 Sep.
This study was designed to compare the quality assurance (QA) results of four dosimetric tools used for intensity modulated radiation therapy (IMRT) and to suggest universal criteria for the passing rate in QA, irrespective of the dosimetric tool used.
Thirty fields of IMRT plans from five patients were selected, followed by irradiation onto radiochromic film, a diode array (Mapcheck), an ion chamber array (MatriXX) and an electronic portal imaging device (EPID) for patient-specific QA. The measured doses from the four dosimetric tools were compared with the dose calculated by the treatment planning system. The passing rates of the four dosimetric tools were calculated using the gamma index method, using as criteria a dose difference of 3% and a distance-to-agreement of 3 mm.
The QA results based on Mapcheck, MatriXX and EPID showed good agreement, with average passing rates of 99.61%, 99.04% and 99.29%, respectively. However, the average passing rate based on film measurement was significantly lower, 95.88%. The average uncertainty (1 standard deviation) of passing rates for 6 intensity modulated fields was around 0.31 for film measurement, larger than those of the other three dosimetric tools.
QA results and consistencies depend on the choice of dosimetric tool. Universal passing rates should depend on the normalization or inter-comparisons of dosimetric tools if more than one dosimetric tool is used for patient specific QA.
本研究旨在比较用于调强放射治疗（IMRT）的四种剂量测定工具的质量保证（QA）结果，并提出不论使用何种剂量测定工具，QA通过率的通用标准。
从五名患者的IMRT计划中选取30个射野，然后分别照射到放射变色胶片、二极管阵列（Mapcheck）、电离室阵列（MatriXX）和电子射野成像装置（EPID）上，进行患者特异性QA。将这四种剂量测定工具测得的剂量与治疗计划系统计算的剂量进行比较。使用γ指数法计算这四种剂量测定工具的通过率，标准为剂量差异3%和距离一致性3毫米。
基于Mapcheck、MatriXX和EPID的QA结果显示出良好的一致性，平均通过率分别为99.61%、99.04%和99.29%。然而，基于胶片测量的平均通过率显著较低，为95.88%。6个调强射野通过率的平均不确定度（1个标准差），胶片测量约为0.31，大于其他三种剂量测定工具。
QA结果和一致性取决于剂量测定工具的选择。如果使用不止一种剂量测定工具进行患者特异性QA，通用通过率应取决于剂量测定工具的归一化或相互比较。
