ABSTRACT
Objective:To compare the calculation result and analyzes the reasons for their differences so as to provide reference for the revision and improvement of the current national standards on radiation shielding design for the room of brachytherapy.Methods:For the initial activity 10 Ci (1 Ci=3.7×10 10 Bq) of radioactive sources, the shielding schemes of brachytherapy room were designed in accordance with UK Institnte of Physics and Engineering in Medicine(IPEM) Report 75, USA NCRP Report 151 and the national standard GBZ/T 201.3-2014, respectively. The differences in shielding limits, occupancy factors and other relevant factors are compared in detail. Results:The annual exposure time in a typical brachytherpy room was about 330 h. The point-specific concrete thickness were 70, 65, 61, 70, 50 cm as required by NCRP Report 151, 41, 43, 30, 40, 39 cm by IREM regulations and 84, 79, 46, 88, 39 cm by GBZ/T 201.3, respectively. The concerned concrete shielding thickness calculated under the GBZ/T 201.3-2014 was generally thicker, with lesser difference from NCRP Report 151 result, whereas that from the IPEM75 report was thinnest. The equivalent lead shielding thicknesses of the protective doors calculated using the three method are 1.170, 0.854 and 1.040 cm, respectively.Conclusions:The shielding thickness calculated using the calculation method and evaluation index recommended by the current Chinese shielding standards for brachytherapy bunker is similar to that reported in NCRP151, but is conservative. In particular, the evaluation index of instantaneous dose equivalent rate required by the current national standards and the relative conservative value of occupancy factor will significantly increase the shielding thickness required by the main shielding area.
ABSTRACT
Objective To explore and establish accurate detection quality control method of source positioning and timer precision for afterloading equipment. Methods The source positioning detection device was made of hd camera,EBT3 disposable film and steel rule,collecting source in each resident point for video images and film. Accurate measurement of radioactive source positioning and timer accuracy, including the timing absolute error and linear error through analysis of image sampling rate. After the film grayscale distribution analysis,comparison between film gray peak position and the measurement of resident point geometry,got the stay point source physics and radiation center deviation. Results Radioactive source physics and radiation center deviation was (-0.33± 0. 10) mm;For all default dwell time,timer average absolute deviation was (0.22±0. 02) s,linear fitting result was y=x-0. 226,R2=1,timing linear error was-0. 01％ Conclusions established detection means through the video images and film exposure quantitative analysis for accurately determination of source positioning,dwell time and source radiation center precision. After experimental testing the machine precision satisfied the requirement of clinical use.
ABSTRACT
This paper discusses the brachytherapy with tumour interventional radiology technology.The structure and security of the intravascular iridium-192 sources afterloader are reviewed in comparison with general afterloader.