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Objective Based on the measurement of the ambient dose equivalent rate of points around the novel self-shielding Zap-X radiotherapy system, its self-shielding effect was evaluated and analyzed, and suggestions were proposed for the revision and improvement of related standards in China. Methods The ambient dose equivalent rates were measured at 15 points around the Zap-X system under 6 system operating conditions. The radiation shielding effect of the Zap-X system was evaluated according to the domestic and international radiation protection standards of radiotherapy equipment. Results Measurement of ambient dose equivalent rate and dose evaluation showed that the shielding effect of the Zap-X system met the requirements of international standards, but the dose rates at some points failed to satisfy the reference control levels in the domestic standards. Conclusion Without the shielded treatment room, the self-shielding effect of the Zap-X radiotherapy system is insufficient to meet the requirements of domestic standards for radiation safety and protection. The system should be operated in the treatment room to meet domestic standards.
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Objective To explore the radiation shielding optimization plan for a medical proton cyclotron developing and commissioning building at various commissioning stages. Methods According to the maximum source termsat different commissioning stages, we used the empirical formula to estimate the instantaneous dose rate at the point of interest outside the shield of the building, and optimized the building’s shielding ateach commissioning stage. Results When adding 1.0 m mobile concrete shielding blocks (“blocks” below) each to wall 3 and wall 4 at the cyclotron commissioning stage, 1.0 m blocks to wall 4 and 1.25 m blocks to wall 5 at the beam transport line commissioning stage, and 1.0 m blocks to wall 9 and 0.4 m blocks to the ceiling at the simulated treatment room commissioning stage, the dose rates at the points of interest outside the shield could meet the dose rate limit requirements. Conclusion The application of mobile concrete shielding blocks not only meets the shielding requirements, but also has economical and space-saving advantages, conforming to the principle of shielding optimization. This can be an approach to the optimization of radiation shielding for high-energy particle accelerators or similar scientific projects.
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OBJECTIVE: To explore the radiation shielding problem of Halcyon linear accelerator room. METHODS: According to the dose estimation method recommended by GBZ/T 201.2—2011 Radiation Shielding Requirements for Radiotherapy room--Part 2: Radiotherapy Room of Electron Linear Accelerators(hereinafter referred to as GBZ/T 201.2—2011) and NCRP report No.151 Structural Shielding Design and Evaluation for Megavoltage X-and Gamma-Ray Radiotherapy Facilities the required shielding thickness of 6.0 MeV Halcyon linear machine room is evaluated and compared with the existing machine room. After the equipment was put into use, we measured and verified the dose equivalent rate around each point. RESULTS: ⅰ) The transmittance of the main beam passing through the self-shielding system was 0.06%. The theoretical shielding thickness of the main beam path sites A, C and L of the accelerator(two main shielding walls and room top sites respectively) was 136.00, 130.00 and 136.00 cm, which was lower than the required shielding thickness of the main shielding area specified in GBZ/T 201.2—2011 for 6.0 MeV accelerator. ⅱ) Compared with the existing equipment rooms in the hospital, except that the thickness of the top secondary shield(80.00 cm) and the thickness of the west section of the outer wall of the labyrinth(100.00 cm) are smaller, the rest meets the shielding requirements. ⅲ) After the transformation of the computer room and the installation of Halcyon linear accelerator, the surrounding dose equivalent rate was lower than the control level required by GBZ/T 201.2—2011. CONCLUSION: The self-shielding design of Halcyon linear accelerator can effectively protect 6.0 MeV rays used for treatment, reduce the shielding thickness required for the main shielding area, reduce the shielding construction cost of the equipment room and increase the usable area of the equipment room.
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Objective To develop the radiation shielding device for an environmental radiation survey meter with an aim to precisely measure local radiation levels and evaluate decontamination effectiveness in Fukushima.Methods A kind of lead alloy was selected as the main material for the shielding device.Attenuation effects of different lead plates and lead cylinders were measured at the radiation regulatory laboratory and in a polluted area of Fukushima,respectively.The whole shielding device was designed on the basis of measurement results,attenuation effects,cost of production and practicability.Results The whole device was composed of main shielding,probe shielding and a bracket with lid.The main shielding was a lead cylinder with 10 cm in height and 3 cm in thickness.The probe shielding was a lead cylinder with 8 cm in height and 2 cm in thickness.The thickness of lid was 1 cm.Conclusions The device can be available to effectively shield the influence of ambient radiation and accurately measure local radiation levels and evaluate decontamination effectiveness.It can play a valuable part in post-disaster reconstruction of contaminated areas in Fukushima.
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A computed tomography (CT) is a powerful system for the effectively fast and accurate diagnosis. The CT system, therefore, has used substantially and developed for improving the performance over the past decade, resulting in growing concerns over the radiation dose from the CT. Advanced CT techniques, such as a multidetector row CT scanner and dual energy or dual source CT, have led to new clinical applications that could result in further increases of radiation does for both patients and workers. The objective of this study was to review the international guidelines of the shielding requirements for a CT facility required for a new installation or when modifying an existing one. We used Google Search Engine to search the following keywords: computed tomography, CT regulation or shield or protection, dual energy or dual source CT, multidetector CT, CT radiation protection, and regulatory or legislation or regulation CT. In addition, we searched some special websites, that were provided for sources of radiation protection, shielding, and regulation, RSNA, AAPM, FDA, NIH, RCR, ICRP, IRPA, ICRP, IAEA, WHO (See in Table 1 for full explanations of the abbreviations). We finally summarized results of the investigated materials for each country. The shielding requirement of the CT room design was very well documented in the countries of Canada, United States of America, and United Kingdom. The wall thickness of the CT room could be obtained by the iso-exposure contour or the point source method. Most of documents provided by international organizations were explained in importance of radiation reduction in patients and workers. However, there were no directly-related documents of shielding and patient exposure dose for the dual energy CT system. Based international guidelines, the guideline of the CT room shielding and radiation reduction in patients and workers should be specified for all kinds of CT systems, included in the dual energy CT. We proposed some possible strategies in this paper.