2015年 · 第35卷第10期

Since its establishment in 1955, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has carried out extensive research work on radiation levels and effects, publishing nearly 30 scientific reports. These reports have served as the basis for the impact assessment of radiation sources by governments and organizations as a scientific basis for the assessment of radiation hazards, the development of radiation protection and safety standards and the management of radiation sources. As Hans Blix, the former Director-General of the International Atomic Energy Agency (IAEA), said at the General Assembly celebrating the 50th anniversary of the Scientific Committee, "the necessary international coherence in security matters cannot be achieved without the tremendous work of UNSCEAR over the years". In order to make more people know about UNSCEAR, on the occasion of the 60th anniversary of the establishment of UNSCEAR, I will briefly introduce the situation of UNSCEAR that the author knows about.

In recent years, the incidence of non-small cell lung cancer (NSCLC) in China has been increasing year by year. At present, surgery is the first choice for the treatment of NSCLC, and accurate preoperative staging, especially regional lymph node staging, is the key to decide whether to operate or not and the surgical plan. Fluorodeoxyglucose (¹⁸F-FDG) PET-CT imaging can simultaneously display anatomical and metabolic information of lesions, reflect the biological activity of tumors, and has unique advantages in the diagnosis and staging of lung cancer. This study explores¹⁸The diagnostic value of F-FDG PET-CT in NSCLC regional lymph node metastasis and its role in lymph node staging.

image-guided radiotherapy (IGRT) is a modern precision radiotherapy technique. In this study, the cone beam CT (CBCT) images before, after and after 6-dimensional bed adjustment were obtained, and the interfractional positioning error and interfractional displacement error of vertebral metastases were calculated, and the expansion margin of CTV-PTV was estimated, which provided a reference for the expansion margin of CTV-PTV in the design of radiotherapy plan for vertebral metastases, so as to improve the positioning accuracy of radiotherapy for vertebral metastases.

In order to check the accuracy of protective level thermoluminescence dose delivery, provide better quality assurance for protective level thermoluminescence dose magnitude delivery, and verify the accuracy, magnitude, procedures and technical capabilities of standard laboratory instruments, the International Atomic Energy Agency/World Health Organization (IAEA/WHO) has specially carried out quality control comparison of protective level thermoluminescence dosimeters (TLDs) in member countries^[1,2,3]。 According to the development status of international radioprotective dose monitoring, the IAEA revised the verification scheme of the protective level dose standard, and proposed that in the future, all participating verification laboratories can only use¹³⁷The TLD samples were irradiated with the Cs γ-ray radiation field instead of using⁶⁰Co γ-ray radiation field^[4]。 China Institute of Metrology (NIM) participated in the comparison in 2012, and the results of the comparison will now be reported.

Under normal operating conditions of nuclear and radiation facilities, gaseous radioactive effluents may be discharged into the environment. Nuclear and radiation operators should assess the dose exposure to critical population groups resulting from planned discharges prior to discharge of radioactive material for which they are responsible to the environment^[1]。 Numerous results have been achieved in the calculation of environmental radiation dose based on monitoring of gaseous effluent emissions after operation of nuclear and radiation facilities^[2,3]While the validation process of emission limits at the design stage is less reported. This study takes a small nuclear technology utilization laboratory as the object to estimate the radiation dose caused by effluent to the surrounding public, and briefly discusses the process of validating emission limits.

Intensity modulated radiotherapy is widely used in clinical practice, which improves the quality of life of cancer patients. Compared with ordinary radiotherapy, the planning and dose distribution of intensity modulated radiotherapy are much more complicated. Therefore, higher requirements are put forward for the quality control and quality assurance of intensity modulated radiotherapy. In 2013, the International Atomic Energy Agency (IAEA) carried out a study on quality control methods for intensity modulated radiotherapy (step 7a), with China as one of the participating countries. Sichuan Province is one of the participating verification units. In this study, the Ono output factor of the multi-leaf grating for intensity modulated radiotherapy was validated using a 0.015 cc ionization chamber and a Unidos dosimeter.

Intensity modulated radiotherapy is one of the new radiotherapy techniques developed in recent years. Under the condition that the radiation field is consistent with the shape of the target area, the wire harness intensity is adjusted according to the three-dimensional shape of the target area and the specific anatomical relationship between vital organs and the target area. The dose distribution in a single radiation field is not uniform, but the dose distribution in the whole target area volume is more uniform than that of three-dimensional conformal treatment. On the basis of three-dimensional conformal irradiation, the conformity of the dose in the target area is increased, and the irradiated dose of normal tissue is reduced. The measurement of Ono output factor and two-dimensional and three-dimensional distribution of Ono absorbed dose formed by multi-leaf grating in intensity modulated radiotherapy is the focus of international clinical radiotherapy. At present, there are reports in China that medical institutions carrying out intensity modulated radiotherapy use two-dimensional semiconductors for dosimetric verification of intensity modulated radiotherapy^[1]； Dose Validation of Intensity Modulated Radiotherapy Plans Using Monte Carlo Procedure (DPM)^[2]。 These dose validations only validate specific patient doses and do not evaluate the correctness of multi-field grating output factors calculated by different radiotherapy planning systems. In 2013, the IAEA joined 18 countries around the world to collaborate on research, and after the application was approved, China was one of the participating countries. To study the methods, techniques and procedures of Ono output factor and two-dimensional and three-dimensional distribution of Ono absorbed dose in multi-leaf grating for intensity modulated radiotherapy. This study reports the calculation of Ono output factor, the measurement of Ono output factor in 0.015 cc ionization chamber and the comparison with the published values in some radiotherapy planning systems of intensity modulated radiotherapy equipment in Jiangsu Province.

In intensity modulated radiotherapy (IMRT), the irradiation field is divided into several sub-fields by a multi-leaf grating, and the sub-fields are small in area. In order to achieve the ideal Ono dose distribution, the output factor of multi-leaf grating Ono is particularly important. In 2012, the American Center for Radiophysics (RPC) published a set of reference data for the Ono output factor of the accelerator multi-leaf grating produced by Varian Company of the United States, Medida Company of Sweden and Siemens Company of Germany, which is used to judge the accuracy of the Ono output factor of the accelerator multi-leaf grating in various medical institutions^[1]。 In this study, according to the requirements of the International Atomic Energy Agency (IAEA) project, the reference data provided by RPC for the Ono output factor of multi-leaf grating of 12 accelerators in Hubei Province is validated.

Radioactive seed implantation is one of the therapeutic methods for early low-risk prostate cancer, and its efficacy is comparable to that of radical surgery or external radiotherapy^[1]However, its advantages are favored by more and more patients and doctors due to less trauma and adverse reactions, shorter treatment time, and lower requirements for equipment and venue. Dose distribution is the most direct and important factor affecting the efficacy of particle implantation^[1,2,3,4], similar to the extent and extent of surgical resection directly affects the tumor control effect and adverse reactions.