背景:使用新电流源的静电计的新质量保证和控制方法,与静电计指南中公布的方法不同,已被报道。这种电流源使用干电池,在电压方面表现出优异的性能,温度,和时间特征。静电计灵敏度系数可以通过将一个静电计的灵敏度与另一个静电计的灵敏度在两种方法中预先由校准实验室校准的静电计校准系数上进行比较来计算。该指南方法需要在设施中设置两组或更多组电离室和静电计。相比之下,我们的方法不使用电离室;因此,静电计的灵敏度比可以在任何设施中测量。这项研究比较了使用新电流源方法(电流方法)计算的静电计灵敏度因子的不确定性与使用静电计指南中描述的线性加速器(LINAC)和电离室(LINAC方法)计算的不确定度。
方法:在本研究中,我们使用了日本川口电力公司以前发明的电流源。用三个制造商的静电计测量静电计的灵敏度比。通过乘以静电计校准系数来计算静电计灵敏度因子。电离室为30013(PTW),电流源是在校准条件下从10MVTrueBeamX射线获得的电流。平均值,标准偏差,并计算变异系数。还测量了设置电离室以计算静电计的灵敏度比所需的时间。通过计算静电计灵敏度系数的扩展不确定度来确认准确性。
结果:LINAC方法的最大变异系数为0.072%。LINAC方法的总时间约为110分钟。当前方法具有0.0055%的最大变异系数,并且所花费的时间小于LINAC方法所花费的时间(35min)的一半,因为在校准条件下没有电离室设置和施加的电压稳定的等待时间。静电计校准系数的扩展不确定度分别为0.36%和0.36%,分别。
结论:使用电流源的静电计灵敏度因子的新交叉比较方法比指南中描述的线性加速器方法更有效和有用;此外,该方法确保了静电计质量保证和控制的准确性。
BACKGROUND: A new quality assurance and control method for electrometers using a new current source, different from the method published in the
guidelines for electrometers, has been reported. This current source uses dry batteries and exhibits excellent performance in terms of voltage, temperature, and time characteristics. The electrometer sensitivity coefficient can be calculated by comparing the sensitivity of one electrometer with that of another on the electrometer calibration coefficient that has been calibrated by a calibration laboratory in advance in both methods. The
guideline method requires two or more sets of ionization chambers and electrometers in the facility. In contrast, our method does not use ionization chambers; therefore, the sensitivity ratio of the electrometer can be measured in any facility. This study compared the
uncertainty of the electrometer sensitivity factor calculated using the new current source method (current method) with that calculated using a linear accelerator (LINAC) and ionization chambers (LINAC method) described in the electrometer
guidelines.
METHODS: In this study, we used a current source that we invented previously by Kawaguchi Electric Works in Japan. The sensitivity ratios of the electrometers were measured with three manufacture\'s electrometers. The electrometer sensitivity factor was calculated by multiplying the electrometer calibration coefficient. The ionization chamber was 30013 (PTW), and the current source was the current obtained from 10 MV TrueBeam X-rays under calibration conditions. The mean value, standard deviation, and coefficient of variation were calculated. The time required to set up the ionization chamber for calculating the sensitivity ratio of the electrometer was also measured. The accuracy was confirmed by calculating the expanded
uncertainty of the electrometer sensitivity coefficients.
RESULTS: The LINAC method had a maximum coefficient of variation of 0.072%. The gross time of the LINAC method was approximately 110 min. The current method had a maximum coefficient of variation of 0.0055% and took less than half the time taken by the LINAC method (35 min) because there was no waiting time for the ionization chamber to be set up and the applied voltage to stabilize under calibration conditions. The expanded uncertainties of the electrometer calibration coefficients were 0.36% and 0.36%, respectively.
CONCLUSIONS: The new cross-comparison method for electrometer sensitivity factors using a current source is more efficient and useful than the linear accelerator method described in the guidelines; furthermore, this method ensured accuracy for quality assurance and control of electrometers.