输出剂量测量时温度气压湿度变化规律的研究

摘要

目的 对加速器周检输出剂量测量时记录的温度、气压、湿度等数据进行回顾分析,研究数据的变化规律.方法 选取2013年~2015年周检对瓦里安Clinac iX加速器输出剂量测量时记录的148组数据,进行回顾研究.对不同年度及不同季节的温度、气压、湿度和空气密度(AD)数据进行统计分析.结果 2013年~2015年,温度、气压、湿度和AD的平均值分别为21.8℃,1017 hPa,46%RH和1.002.不同年度的相同时期,各类数据总体上变化不大.同一年度,气压值的变化呈V形,湿度和AD值的变化呈倒V型.同一年度的不同季节,温度平均值变化不大;气压平均值,夏季最低,冬季最高;湿度平均值和AD平均值,夏季最高,冬季最低.结论 气压、湿度和AD值,与季节的变化相关.物理师应充分认识温度、气压和湿度的变化规律,准确记录相关数据,从而获取准确的输出剂量值.%Objective To retrospectively investigate the variation laws of temperature, atmospheric pressure and humidity when measuring the output dose of linac in weekly QA-tests. Methods A total of 148 sets of data recorded in weekly quality assurance (QA)-tests outputted from the Varian Clinac iX linac from 2013 to 2015 were selected for retrospective analysis. Statistical analysis was applied to compare the data of temperature, atmospheric pressure, humidity and air density (AD) in different years and seasons. Results The mean values of the 4 parameters from 2013 to 2015 were 21.8℃, 1017 hPa, 46% RH and 1.002, respectively. There were no significant changes of these parameters in the same period of different years. In the same year, values of atmospheric pressure were V-shaped, while values of both humidity and AD were inverted V-shaped. In different seasons of the same year, mean values of temperature varied a little; mean values of atmospheric pressure were lowest in summer and highest in winter; mean values of both humidity and AD were highest in summer and lowest in winter. Conclusion Values of atmospheric pressure, humidity and AD have relationship with seasonal variation. Medical physicists should fully understand the variation laws of temperature, atmospheric pressure and humidity, record these parameters accurately, to obtain correct dose values.