利用井型电离室测量后装放射源192Ir活度的方法及放射源活度的验证-《中国医学物理学杂志》

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Title:: Method of measuring the activity of 192Ir radioactive source for afterloading brachytherapy using well-type ionization chamber and quality assurance of the activity of radioactive source

文章编号:: 1005-202X（2021）04-0416-06

作者:: 罗斌1; 2; 李贤富1; 2; 郭飞2; 曹璐2; 许鹏2; 谢力2; 阳华东2; 1.医学影像四川省重点实验室，四川省肿瘤学重点学科，四川南充 637000； 2.川北医学院附属医院肿瘤科，四川南充 637000

Author(s):: LUO Bin1; 2; LI Xianfu1; 2; GUO Fei2; CAO Lu2; XU Peng2; XIE Li2; YANG Huadong2; 1. Sichuan Key Laboratory of Medical Imaging, Key Disciplines of Oncology in Sichuan Province, Nanchong 637000, China 2. Department of Oncology, Affiliated Hospital of North Sichuan Medical College, Nanchong 637000, China

关键词:: 井型电离室; 放射源192Ir; 活度; 验证

Keywords:: Keywords: well-type ionization chamber 192Ir radioactive source activity verification

分类号:: R312；R811.1

DOI:: DOI:10.3969/j.issn.1005-202X.2021.04.004

文献标志码:: A

摘要:: 目的：阐述井型电离室测量后装放射源活度的理论基础和具体测量方法，对所使用的192Ir放射源活度进行验证。方法：首先通过井型电离室系统校准因子计算得出电离室电流与192Ir活度之间的换算系数，然后制定计划寻找192Ir源测量活度的有效驻留点。再利用PTW Unidos E剂量计和PTW SOURCECHECK 4π井型电离室测量192Ir照射电离室后产生的电流并转换为放射源活度。连续测量7个月，测量值与计划系统计算值两组数据进行配对样本t检验，分析两组数据差异。结果：在总共14次的测量计算中，川北医学院附属医院新购进192Ir源活度的测量值与计划系统计算值相对误差均在±1%以内。其最大偏差为0.946%，符合国标WS 262-2017后装γ源近距离治疗质量控制检测规范中源活度稳定性检测±5%内的要求，达到了AAPM临床应用192Ir源活度标定小于±3%的标准。且两组数据配对样本t检验显示，差异无统计学意义（P=0.665>0.05）。结论：井型电离室能够准确测量192Ir源的活度，本院所使用的放射源按照理想的半衰期衰变，放射源杂质少、纯度高。

Abstract:: Abstract: Objective To describe the theoretical basis and specific method of measuring the activity of radioactive source for afterloading brachytherapy using well-type ionization chamber, and to conduct a verification for the activity of 192Ir radioactive source. Methods The conversion coefficient between ionization chamber current and 192Ir source activity was firstly calculated by the calibration factor of well-type ionization chamber system, and then a plan was made to find the effective residence point for the measurement of 192Ir source activity. The current generated by 192Ir source on the effective residence point irradiated on the ionization chamber was measured by PTW Unidos E dosimeter and PTW SOURCECHECK 4 π well-type ionization chamber, and the obtained current was converted into source activity. After 7 months of continuous measurement, paired sample t-test was conducted on the measured data and the calculated data for analyzing the differences between two groups of data. Results The relative deviations between the measured data and the calculated data of newly-purchased 192Ir source in Affiliated Hospital of North Sichuan Medical College were all within ±1% in 14 measurements, with a maximum deviation of 0.946%, which met the requirements of the source activity stability test (within ±5%) of WS 262-2017 specification for testing of quality control in gamma-ray sources afterloading brachytherapy and reached the standard of 192Ir source activity calibration (within±3%) of AAPM clinical application. Moreover, the results of paired sample t-test showed that there was no significant difference between the measured data and the calculated data (P=0.665>0.05). Conclusion Well-type ionization chamber can be used to accurately measure 192Ir source activity. The radioactive source used in Affiliated Hospital of North Sichuan Medical College decays according to the ideal half-life, with less impurities and high purity.

《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]

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