医用直线加速器早晚绝对剂量输出稳定性对比分析

Comparative analysis on morning and evening absolute dose output stability of medical linear accelerator

目的医科达医用直线加速器的监测电离室是开放的,温度、气压和湿度等环境因素可能影响绝对剂量输出的稳定性。分析医科达SYNERGY型医用直线加速器早晚各档能量绝对剂量输出稳定性特点。方法根据IAEA TRS-277号报告对医用直线加速器各档能量进行绝对剂量校准,并用WI3型固体水在相同测量条件下,进行连续52 d早晚各1次的重复测量,期间每周随机进行1次水箱测量来验证使用WI3型固体水测量值的准确性。结果所有能量档中WI3固体水与水箱测量最大偏差为0.5%;各档能量日稳定性最大偏差分别为:-2.0%(6MV)、1.9%(15MV)、1.8%(6Me V)、-2.4%(8Me V)、-2.3%(10Me V)、-2.0%(12Me V)、2.1%(15Me V);早晚配对t检验中6MV、15MV、8Me V和10Me V档能量差异有统计学意义(P<0.05),但无临床意义;6Me V、12Me V和15Me V档能量差异无统计学意义(P>0.05)。结论医科达SYNERGY型医用直线加速器绝对剂量输出稳定性良好。

Objective The ionization chamber of ELEKTA medical linear accelerator monitoring is open to environmental factors such as temperature,air pressure,and humidity that may affect the stability of absolute dose output. The article aimed to analyze the morning and evening absolute dose output stability at different energies of ELEKTA SYNERGY medical linear accelerator. Methods The absolute doses at different energies of medical linear accelerators were calibrated according to the IAEA TRS-277 report,and WI3 type solid water was used to perform repeated measurements in the morning and in the evening for 52 consecutive days under the same measurement conditions,during which a water tank measurement was conducted at random intervals per week to verify the accuracy of WI3 solid water measurements. Results The maximum deviation of WI3 solids water and tank measurement at all energies was0.5% and the maximum deviations of daily energy stability at different energies were：-2. 0%（ 6 MV）,1. 9%（ 15 MV）,1.8%（ 6 MeV）,-2.4%（ 8 MeV）,-2.3%（ 10 MeV）,-2.0%（ 12 MeV）,2.1%（ 15 MeV）. The differences of 6 MV,15 MV,8 MeV,and10 MeV energies in morning and evening paired t tests were statistically significant（ P〈0.05） without clinical significance,while no statistic significance was found in the differences of 6 MeV,12 MeV,and 15 MeV energies（ P〈0.05）. Conclusion Elekta Synergy medical linear accelerator shows excellent stability in absolute dose output.