Objective:An integrated automatic quality control system(automatic quality control instrument)for high dose rate(HDR)afterloader was independently developed.This system was used to measure the placement accuracy,residence time and activity of the radioactive source,so as to assess the accuracy and stability of this system in quality assurance.Methods:The automatic quality control system was connected to the Flexitron type of HDR afterloader through a connecting tube.Quality assurance(QA)plans with different resident positions,clearances,and times were designed for measurement and verification.The measurement length was 1079-1119 mm,and the measurement time was 2-10 s,and the measurement activity was 14,326-28,653 μGy·m2·h-1.The measurements were repeated once per one week in three months,so as to determine the consistency of the measurement parameters in a longer period of time.The measurement results of the placement accuracy,resident time and activity of radioactive source of the HDR 192Ir radioactive source were analyzed.Results:The plate ionization chamber was used to measure the activity of radioactive source.In three months,the measurement deviation of the activity of radioactive source was 1.17%,and the fitted activity decay curve was consistent with the expected decay curve of radioactive source.The measurement accuracies of the positioning of radioactive source were respectively 0.46,0.18,0.23,0.25,and 0.15 mm when the interval step sizes of resident times were respectively 2,3,5,8,and 10 mm,all of them were<1 mm.The measurement accuracy of time was(4.90±0.04)s when the resident time was 5 s.In the measurement accuracy of different resident times(1,2,3,5 and 10s)of same step size,the deviation of them was less than 0.5s.When the resident time was the shortest,the deviation between the read-out value of the automatic system software of quality control and the actually resident time was(0.09±0.04)s.The measurement accuracy gradually stabilized with the increasing of resident times.Conclusion:The automatic quality control instrument can complete the measurements for the positioning accuracy,the accuracy of resident time and the activity of radioactive source,and achieve rapidly and accurately periodic quality assurance.

Objective:An integrated automatic quality control system(automatic quality control instrument)for high dose rate(HDR)afterloader was independently developed.This system was used to measure the placement accuracy,residence time and activity of the radioactive source,so as to assess the accuracy and stability of this system in quality assurance.Methods:The automatic quality control system was connected to the Flexitron type of HDR afterloader through a connecting tube.Quality assurance(QA)plans with different resident positions,clearances,and times were designed for measurement and verification.The measurement length was 1079-1119 mm,and the measurement time was 2-10 s,and the measurement activity was 14,326-28,653 μGy·m2·h-1.The measurements were repeated once per one week in three months,so as to determine the consistency of the measurement parameters in a longer period of time.The measurement results of the placement accuracy,resident time and activity of radioactive source of the HDR 192Ir radioactive source were analyzed.Results:The plate ionization chamber was used to measure the activity of radioactive source.In three months,the measurement deviation of the activity of radioactive source was 1.17%,and the fitted activity decay curve was consistent with the expected decay curve of radioactive source.The measurement accuracies of the positioning of radioactive source were respectively 0.46,0.18,0.23,0.25,and 0.15 mm when the interval step sizes of resident times were respectively 2,3,5,8,and 10 mm,all of them were<1 mm.The measurement accuracy of time was(4.90±0.04)s when the resident time was 5 s.In the measurement accuracy of different resident times(1,2,3,5 and 10s)of same step size,the deviation of them was less than 0.5s.When the resident time was the shortest,the deviation between the read-out value of the automatic system software of quality control and the actually resident time was(0.09±0.04)s.The measurement accuracy gradually stabilized with the increasing of resident times.Conclusion:The automatic quality control instrument can complete the measurements for the positioning accuracy,the accuracy of resident time and the activity of radioactive source,and achieve rapidly and accurately periodic quality assurance.