医用电子直线加速器照射野的日常质量保证

Daily Quality Assurance of Linac Radiation Field

目的通过分析照射野特性相关参数的日检数据的变化趋势,探讨医用电子直线加速器照射野的日常质量保证方法的可行性和必要性。方法每天放射治疗前,用二维电离室矩阵DailyQA3测量加速器照射野特性相关参数与预设标定值的偏差,辅以IBA公司的剂量仪DOS1进行绝对剂量验证和用慢感光胶片进行光野一致性的二次验证,并对以上各项日常检测数据(2009年11月28日-2011年4月8日)进行回顾性分析。结果 X线和电子线输出剂量均随着时间的增加逐渐增大,光野一致性、射野平坦度及对称性基本保持不变。结论一年多的实践表明,本文论述的照射野日常质量保证方法是有效和可行的,它在保证每日放疗精确执行的同时,也为加速器的长期校准提供了依据。

Objective To evaluate the clinical feasibility of daily quality assurance for linac radiation field by analyzing the trend o the daily testing data about parameter of radiation field. Methods Two-dimensional ion chamber array Daily QA3 was used to measure the difference between the practical value and the standard value of the parameter about radiation field before commencing daily treatment. Farmer type ionization chambers from IBA Co. with DOSE1 dosimeter was used fo the absolute dosimetry of photon and electron beams. Light/radiation field coincidence was checked by using films eveR month. The daily testing data（from 11/28/2009 to 4/8/2011） were reviewed and analyzed. Results X- ray and electror output was increasing steadily; light/radiation field coincidence, beam flatness constancy and symmetry of X- ray anc electron was keeping stable, Conclusion The procedures for daily quality assurance of linac radiation field, which wil provide reference for long term linac calibration, are feasible in our experience.