MatriXX系统在放疗质控中的应用研究

Research of the Application of MatriXX System in Radiation Therapy Quality Control

目的探讨二维空气电离室矩阵MatriXX系统进行放疗质控监测的准确性、可靠性和方便性。方法用MatriXX系统在固体水模块中测量医用加速器X射线射野的百分深度剂量(PDD)、组织最大比(TMR)、离轴比、半影和射野宽度,并与RFA300三维水箱扫描结果进行对比分析。MatriXX与自制剂量测量体模相结合验证Pinnac3V8.0m三维放疗计划系统设计的静态调强和动态调强放疗计划。结果MatriXX在固体水中所测6MV X射线的PDD和TMR曲线与RFA300水箱扫描曲线基本平行,15MV X射线的PDD曲线与三维水箱扫描结果几乎重合。用MatriXX所测射野半影比三维水箱扫描值大两倍左右,当射野小于3cm×3cm时MatriXX不能自动计算出半影值。MatriXX可在最短采样时间20mS内同时获得射野离轴比、对称性、平坦度、野宽等信息,并能快速准确地完成调强放疗计划二维剂量分布的定量和定性验证。结论MatriXX在放疗质控测量时具有准确、简便、高效的优势,是较为理想的放疗质控工具。

Objective To investigate the accuracy, reliability and convenience of 2 - D ionization chamber array MatriXX system in daily quality control of radiation therapy. Methods The percent depth dose （PDD） , tissue maximum ratio （TMR） , off-axis ratio profile, penumbra and field width of Varian 23EX linac were measured by MatriXX system combined with solid water phantom and compared with the data acquired by RFA300 three - dimensional water phantom. The dose distri- butions of static and dynamic intensity modulated radiation therapy （IMRT） plans created by Pinnac3 V8.0m three - dimen- sional treatment planning system （3D -TPS） were validated by MatriXX combined with the dose phantom made in home. Results The PDD and TMR of 6MV X - ray measured by MatriXX system were parallel to the curves acquired by RFA300, and the PDD curve of 15MV X - ray measured by MatriXX was nearly identic to that measured by RFA300. The values of penumbra measured by MatriXX were two or three times larger than those measured by RFA300, and when the field size was smaller than 3cm×3cm the penumbra of it could not be automatically calcuiatod out by the MatriXX system. The characteristic information of field, such as symmetry and flatness and field width, can be acquired at once in a single sampling, which can be completed in less than 20mS. The qualitative and quantificational verification of 2 - D close distribution of IMRT plans can be quickly implemented by using MatriXX system. Conclusions The MatriXX system is very accurate and convenient and effective in quality control of clinical radiotherapy, and it＇ s a perfect tool for the quality control procedure of radiation therapy.