Objective: To study the effect of cobalt-60 gamma-ray (⁶⁰Co-γ) radiation on the structure of Nialamide, compare the anti-inflammatory activity of irradiation products, and explore the mechanism of action. Methods: After ⁶⁰Co-γ irradiation of nialamide at a dose of 50 kGy, five known compounds were obtained (2-6). The viability of RAW 264.7 (mouse mononuclear macrophage leukemia) cells treated with these compounds was determined by CCK-8 assay. The secretion of interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and prostaglandin E2 (PGE₂) and the content of nitric oxide (NO) were measured using enzyme-linked immunosorbent assay and Griess method. The production of reactive oxygen species (ROS) was detected using DCFH-DA fluorescent probe. The expression levels of cell-induced nitric oxide synthase (iNOS), cyclooxygenase (COX-2), nuclear transcription factor-κB (NF-κB), and IκB were detected using Western blot. Results: The products of nialamide after irradiation did not significantly affect RAW264.7 cell viability (P > 0.05) but showed a strong anti-inflammatory effect (P < 0.01). Compared with nialamide, compounds 2, 3, 4, 6 significantly reduced NO content in LPS-induced RAW 264.7 cells (P < 0.01), and compound 4 had the most significant effect. Moreover, compound 4 significantly reduced the content of IL-6, TNF-α, PGE₂, and ROS (P < 0.05) as well as the expression of iNOS, COX-2, NF-κB, and IκB (P < 0.05) in LPS-induced RAW 264.7 cells. Conclusion: The chemical structure of nialamide is changed after irradiation with ⁶⁰Co-γ, and its product compound 4 shows strong anti-inflammatory activity, which may be related to inhibiting the activation of NF-κB signaling pathway and reducing the release of inflammatory factors. Radiation technology can provide new insights into the changes of molecular structures and physiological properties of natural products.

Objective: To analyze the basic situation of medical radiation resource allocation in Hefei, and provide the basis for the health administrative department in the generation of development plans and policies related to radiological diagnosis and treatment resources. Methods: Based on the 2022 Hefei Radiological Health Monitoring Project, the survey used a questionnaire on the basic situation of radiological diagnostic and treatment institutions to investigate the types and quantities of radiological diagnostic and treatment equipment, the number of radiological staff, and the provision of personal protective equipment of radiological diagnostic and treatment institutions at various levels. Results: There were totally 426 radiological diagnosis and treatment institutions, 3345 radiation workers, and 1069 sets of radiological diagnosis and treatment equipment in Hefei. There were 22 (5.16%) tertiary radiological diagnosis and treatment institutions and a total of 2511 (75.07%) radiation workers in these institutions. There were 336 primary and unclassified radiological diagnosis and treatment institutions and a total of only 404 (12.08%) radiation workers in these institutions. For each radiological diagnostic and treatment device, tertiary hospitals were equipped with 6.20 radiological workers, secondary hospitals with 2.06 radiological workers, and primary and unclassified hospitals with 1.23 radiological workers. The number of workers allocated per device was significantly higher in tertiary hospitals than in secondary and primary/unclassified hospitals. The quantity of various types of radiation protection supplies was generally sufficient to meet the needs for conducting radiological diagnostic and treatment procedures. Conclusion: From this survey, it was evident that the city of Hefei had a relatively abundant allocation of radiological diagnostic and treatment resources. However, there were two main characteristics observed in the distribution of medical radiation resources across the city: uneven distribution among medical institutions of different levels and among various districts and counties. Therefore, it was recommended that the government and health administrative departments adjusted the policies regarding the allocation of medical radiation resources and large medical equipment to ensure scientific and rational deployment of radiological diagnostic and treatment equipment.

Objective: To investigate the radioprotection and management of yttrium-90 resin microsphere therapy based on the survey and monitoring of treatment institutions in Guangdong Province, China, and to provide technical reference and basis for the subsequent radiation management of this therapy. Methods: Based on the technical data on yttrium-90 resin microsphere therapy collected from both domestic and international sources, an investigation was conducted on some yttrium-90 resin microsphere treatment institutions in Guangdong Province. Radiation level monitoring was carried out in the radioactive workplaces of three hospitals that had conducted yttrium-90 resin microspheres therapy. Environmental X-γ dose rate meters were used for detecting radiation dose equivalent rates, while α and β surface contamination monitors were used for detecting radioactive surface contamination. Additionally, urine samples from two patients were collected within 24 hours post-operation, and total radioactivity was analyzed using low-background α and β counters. Results: During the yttrium-90 resin microsphere therapy, the radiation dose equivalent rates around the digital subtraction angiography rooms in the three hospitals ranged from 0.15 to 0.26 μSv/h, and the radiation dose equivalent rates around the observation wards ranged from 0.17 to 0.69 μSv/h. The β radioactive surface contamination values in the workplace control zones ranged from ＜0.07 to 18.7 Bq/cm², while the values in the supervised zones were all less than 0.07 Bq/cm². The total β radioactivity in the urine of the two patients within 24 hours post-operation accounted for approximately 0.0010% to 0.0013% of the yttrium-90 infusion dose. Conclusion: The radiation levels at the monitoring sites in the workplaces of the three hospitals are below the national standard limits. The radioprotection and management of yttrium-90 resin microsphere therapy in the three hospitals in Guangdong Province are satisfactory.

Objective: To investigate the levels and variations of radon concentration in Wuhan subway and to provide data support for ensuring public radiation safety. Methods: The typical sampling method was used to select 18 stations from Wuhan Metro Line 2, Line 3, and Line 7 for the measurement and evaluation of radon in the air. Using RAD7 electronic radon detector and continuous radon measurement method, radon concentrations in station platforms and station halls were investigated. Analysis of variance and t test were used for statistical analysis. Results: The concentration of radon in Wuhan subway ranged from 8.8 to 16.2 Bq/m³, with an average of 11.5 Bq/m³, which is far lower than the limit set by Requirements for Radiological Protection for Radon in Public Underground Structure and Using Geothermal Water (WS/T 668-2019). There was no significant difference in radon concentration between station platform and station hall (t = −0.081, P > 0.05). There was no significant difference in radon concentration between different lines (F = 0.338, P > 0.05). On the whole, the radon concentration in summer was lower than that in winter, and there was no significant difference between months (F = 1.280, P > 0.05). Conclusion: The radon concentrations in Wuhan subway result in low-dose radiation, and there is no significant health risk of radon exposure.

Objective: To investigate air radioactivity contamination, surface contamination, ambient dose equivalent rates, and radiation doses to individuals in the treatment room during ¹⁷⁷Lu-DOTATATE therapy. Methods: A ward for ¹⁷⁷Lu-DOTATATE therapy was selected in the nuclear medicine department of a general hospital. Air and surface radioactivity samples were collected before and after therapy for four patients. Ambient dose equivalent rates were measured around the four patients following the initiation of ¹⁷⁷Lu-DOTATATE therapy. Measurements were taken at distances of 0.1, 0.3, 0.5, and 1−4 m (with 0.5 m intervals) from the right lateral midsection of the patient’s torso. The measurement time points included 5, 15, and 30 min after initiation of administration, as well as 0−4 h (with 1 h intervals), 24 h, and 48 h post-administration. Radiation exposure doses for personnel at different distances from the patients were calculated for each time interval. Results: The results of radioactive aerosol detection for all four patients during and after the administration of ¹⁷⁷Lu-DOTATATE were similar to those before administration. Surface contamination was not detected at the measurement locations except for patient number 2. The ambient dose equivalent rates increased with increasing injection dose during the administration. However, the ambient dose equivalent rates decreased significantly within one hour after administration. At the end of the administration, the average ambient dose equivalent rate at a distance of one meter for the four patients was 42.931 μSv/h. From the start of administration to four hours post-administration, personnel maintaining a distance of one meter from the patient received a total radiation dose of 167.64 μSv. Conclusion: Air radioactivity contamination does not occur during ¹⁷⁷Lu-DOTATATE therapy. However, measures should be taken before the commencement of therapy to address potential surface contamination. Both accompanying persons and healthcare staff receive radiation doses below the stipulated dose constraints throughout the treatment process. Therefore, it is necessary to implement appropriate measures to minimize the radiation exposure of healthcare staff.

Objective To track and evaluate the implementation of the Radiation Shielding Requirements in Room of Radiotherapy Installations—Part 1: General Principle (GBZ/T 201.1–2007) among relevant personnel in medical radiation institutions, and to provide a scientific basis for revising the standard. Methods According to the Guidelines for Health Standards Tracking Evaluation (WS/T 536–2017) and the implementation protocol of standard evaluation, an online survey was conducted among 212 relevant workers from 146 medical radiation institutions across 18 provinces in China. The data were aggregated and analyzed with the use of Microsoft Excel 2010. Results A total of 215 questionnaires were returned, of which 212 were valid. Among the valid respondents, 77.8% believe that this standard is universally applied; 96.2% believe that this standard can meet work needs; 63.7% have participated in relevant training on this standard; 74.1% use this standard once or more per year; and 10.8% believe that this standard needs to be revised. Conclusion Medial radiation workers have a high rate of awareness of the basic information and content of the standard, but the understanding and application of the standard content need to be improved. We recommend that relevant departments further strengthen the promotion of and training on the standard, revise some content based on actual situation, and improve workers’ ability to use the standard.

Objective: To evaluate the efficiency of colored Doppler ultrasound for the differential diagnosis of benign and malignant thyroid nodules. Methods: A total of 150 patients with thyroid nodules admitted to Wuwei Municipal People’s Hospital, Anhui Province, China during the period from July 2018 to December 2023 were enrolled. All patients underwent colored Doppler ultrasound of the thyroid gland and pathological examination of the thyroid nodules. The pathological examination of the thyroid nodules served as a gold standard to evaluate the value of colored Doppler ultrasound for the differential diagnosis of benign and malignant thyroid nodules. In addition, the value of different ultrasound image features for differential diagnosis of benign and malignant thyroid nodules was evaluated. Results: With the pathological examination of the thyroid nodules as a gold standard, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the colored Doppler ultrasound were 100.00%, 95.87%, 85.29%, 95.87%, and 96.67% for the differential diagnosis of benign and malignant thyroid nodules. For differential diagnosis of benign and malignant thyroid nodules, a > 1 ratio of longitudinal to transverse diameters of thyroid nodules, irregular margin, and microcalcification showed a 100.00% sensitivity, irregular acoustic halos showed a 100.00% specificity, and microcalcification had the highest accuracy (98.00%). Conclusion: Colored Doppler ultrasound has a high value for the differential diagnosis of benign and malignant thyroid nodules. A > 1 ratio of longitudinal to transverse diameters of thyroid nodules, irregular margin, and microcalcification provide valuable insights into the differentiation between benign and malignant thyroid nodules.

Objective: To investigate the basic conditions of non-medical radiation institutions and their current status of occupational health management of radiation workers and radiation protection in workplaces in Tianjin City, China, and to clarify the key points of occupational health management and radiation protection efforts. Methods: A comprehensive survey was conducted to assess the basic conditions of non-medical radiation institutions and their status of occupational health management for radiation workers across 16 districts in Tianjin in 2023. Then, some non-medical radiation institutions were chosen according to their industrial sections as sentinel institutions to investigate radiation protection in workplaces. Results: In 2023, there were a total of 431 non-medical radiation institutions in 16 districts of Tianjin, primarily in the industries of nuclear instrument, industrial radiography, and others. In these institutions, there were a total of 5264 radiation workers, with 93.8%, 93.0%, and 93.7% participating in the training of radiation protection, the occupational health examination, and the personal dose monitoring, respectively. Eighty-six non-medical radiation institutions were chosen as the sentinel institutions for investigation of radiation protection conditions in workplaces. The resulting data met the stipulated limits according to relevant standards. Conclusion: The current status of occupational health management and radiation protection in non-medical radiation institutions in Tianjin is satisfactory. However, there is a need for further management enhancements, particularly in key industries such as nuclear instrumentation and industrial radiography.

With the rapid development of radiotherapy technology, the therapeutic outcomes of tumor patients have improved significantly, enabling effective disease control. However, during radiotherapy, the skin as the first barrier of the human body is inevitably exposed to radiation, leading to superficial skin injury. This injury often manifests as blistering, cracking, bleeding, and ulceration, resulting in wounds that are difficult to heal and potentially affecting the effectiveness of the treatment. At present, the therapeutic effect of drugs on radiation-induced skin injury remains limited, and the development of new drugs depends on the elucidation of the mechanisms. Therefore, it is crucial to investigate the mechanisms of radiation-induced skin injury. This article reviews these mechanisms, including DNA damage, oxidative stress, inflammatory response, and vascular damage and fibrosis, and summarizes the therapeutic drugs and targeted proteins in recent years, aiming to provide a reference for the further development and clinical application of drugs for radiation-induced skin injury.

Breast cancer is one of the major cancers affecting women globally. Although the five-year survival rate is very high, it is one of the most common causes of cancer-related deaths. Surgery, systemic therapy, and radiotherapy are the three pillars of radical treatment of breast cancer. However, for breast cancer patients who have undergone initial radiotherapy, many experience relapse or develop secondary cancers in the previously treated areas. These patients need to be treated again, and re-irradiation and hyperthermia are important treatment methods for recurrent breast cancer. Radiotherapy can be combined with local hyperthermia to make tumor cells sensitive to radiation, thereby reducing the required radiation dose. The combination of mild local hyperthermia and re-irradiation with reduced total dose is a treatment option for breast cancer patients who have previously received radiation. The combination of re-irradiation and hyperthermia is currently a hotspot of comprehensive tumor treatment. This article summarizes the research progress on the sequence of recurrent breast cancer and the optimal temperature of hyperthermia in treatment with re-irradiation and hyperthermia. Specifically, this article reviews the definition and type of re-irradiation and hyperthermia, the common radiotherapy methods for various types of recurrent breast cancer, and the effect of radiotherapy, hyperthermia, or their combination on the immune phenotype of tumor cells and its mechanism. Our results provide a scientific basis for the evaluation of the optimal efficacy of re-irradiation combined with hyperthermia in treating recurrent breast cancer.

Objective: To compare artificial intelligence-assisted diagnostic system and conventional manual CT image interpretation for detection of positive pulmonary nodules and differential diagnosis of benign and malignant pulmonary nodules, and to provide a reference for the application of artificial intelligence in clinical screening for lung cancer. Methods: Patients who underwent chest CT scans for pulmonary nodules from March 2019 to December 2023 were enrolled. The CT images were subjected to artificial intelligence-based and conventional manual CT image interpretation. The pathological examination results of pulmonary lesions served as a gold standard for comparison of artificial intelligence-based and conventional manual CT image interpretation in detection rate of positive pulmonary nodules and differential diagnosis of benign and malignant pulmonary nodules. Results: A total of 327 positive pulmonary nodules were identified in 207 patients. The detection rate of positive pulmonary nodules was significantly higher with artificial intelligence-based CT image interpretation than with conventional manual CT image interpretation (95.72% vs. 86.85%; χ²=16.16, P < 0.01). Moreover, artificial intelligence-based CT image interpretation showed significantly higher detection rates for solid (χ²=7.71, P < 0.01) and ground-glass pulmonary nodules (χ²=5.80, P < 0.05) than conventional manual CT image interpretation. The detection rates for pulmonary nodules with < 1 cm (χ²=4.97, P < 0.05), 1 to < 2 cm (χ²=7.04, P < 0.01), and 2 to < 3 cm (χ²=4.91, P < 0.05) diameters were significantly higher with artificial intelligence-based CT image interpretation than with conventional manual CT image interpretation. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for differential diagnosis of benign and malignant pulmonary nodules were 98.08%, 91.53%, 95.33%, 96.43%, and 95.71% with artificial intelligence-based CT image interpretation and 91.34%, 77.97%, 87.96%, 32.62%, and 86.50% with conventional CT image interpretation. The sensitivity (χ²=4.70, P < 0.05), specificity (χ²=4.20, P < 0.05), negative predictive value (χ²=65.28, P < 0.01), and accuracy (χ²=8.52, P < 0.01) were significantly higher with artificial intelligence-based CT image interpretation than with conventional manual CT image interpretation. However, there was no significant difference in the positive predictive value (χ²=3.80, P > 0.05). Conclusion: Compared with conventional manual CT image interpretation, artificial intelligence-assisted diagnostic system for CT image interpretation can significantly increase the detection rate of positive pulmonary nodules and improve the efficiency of differential diagnosis of benign and malignant pulmonary nodules, so it deserves widespread applications in physical examination and early screening for lung cancer.

Objective: To investigate the effects of occupational exposure to ionizing radiation on blood indicators of radiation workers, and to provide evidence for occupational health monitoring. Methods: This study included 3853 radiation workers who participated in occupational health examination in Gansu Provincial Center for Disease Control and Prevention from January 1, 2021 to December 31, 2022. The results of fasting blood glucose, renal function, liver function, white blood cell count, platelet count, and lymphocyte micronucleus were analyzed. Results: The detection rates of abnormal fasting blood glucose and liver function were significantly higher in males than in females (P < 0.05), and the detection rates of abnormal renal function, white blood cell count, platelet count, and lymphocyte micronucleus were significantly lower in males than in females (P < 0.05). The detection rates of abnormal fasting blood glucose, liver function, and lymphocyte micronucleus were significantly higher in radiation workers with ≥ 21 years of working experience than those with ≤ 10 years of working experience (P < 0.05). The detection rate of abnormal fasting blood glucose was significantly higher in the non-medical group than in the diagnostic radiology, radiation therapy, and interventional radiology groups (P < 0.05). The detection rate of abnormal fasting blood glucose was significantly higher in the primary medical institution group than in the tertiary medical institution group (P < 0.05). The detection rate of abnormal liver function was significantly higher in the primary medical institution group than in the secondary and tertiary medical institution groups (P < 0.05). Conclusion: Long-term occupational exposure to ionizing radiation may cause radiation damage to the human body. Health education should be strengthened for non-medical and male radiation workers to prevent the occurrence of chronic metabolic diseases.

Objective: Analyze and compare the therapeutic value of contrast-enhanced ultrasound (CEUS) and enhanced spiral CT in patients with primary hepatocellular carcinoma (PHC) undergoing transcatheter arterial chemoembolization (TACE). Methods: A retrospective analysis was conducted on 108 PHC patients (122 lesions) treated at Beijing Shijitan Hospital affiliated with Capital Medical University from July 2021 to June 2023. All patients were treated with TACE. After treatment, CEUS and contrast-enhanced spiral CT examinations were performed to evaluate the inactivation status of tumor lesions, with pathological results as the gold standard. The receiver operating characteristic curve and decision tree model were used to comprehensively evaluate the diagnostic value of CEUS, contrast-enhanced spiral CT, and their combination in PHC. Results: The pathological results showed that 79 lesions remained active (positive) and 43 lesions were completely inactivated (negative). The areas under the receiver operating characteristic curve for evaluating PHC treatment efficacy by CEUS, contrast-enhanced spiral CT, and their combination were 0.975, 0.918, and 0.994, respectively. The sensitivity, positive predictive value, and actual application accuracy of CEUS and the combined method were higher than those of contrast-enhanced spiral CT (P < 0.05). A decision tree diagnostic model for PHC treatment efficacy was constructed using CEUS, contrast-enhanced spiral CT, and their combination as independent variables and PHC treatment efficacy as the dependent variable. The misjudgment rates were 3.3%, 10.7%, and 0.8%, respectively, and the prediction accuracy was 96.7%, 89.3%, and 99.2%, respectively. Conclusions: CEUS and the combination of CEUS and contrast-enhanced spiral CT have high evaluation value for PHC treatment efficiency.

With the vigorous development of the nuclear industry, the perfection and professionalization of China’s nuclear emergency response system are becoming increasingly crucial. The national nuclear emergency response system is divided into three levels: the national level, the level of provinces (autonomous regions or centrally administered municipalities) with nuclear installations, and the level of operators of nuclear installations. Nuclear emergency response organizations in prefecture-level cities play an indispensable role within the provincial nuclear emergency response organizations and are the vanguard force responsible for off-site nuclear emergency response, with advantages such as familiarity with the off-site environment and rapid response initiation. As the number of nuclear power units increases, especially with a single prefecture-level city hosting multiple nuclear bases, the existing nuclear emergency response capabilities and systems in prefecture-level cities urgently need to be updated and strengthened. Through in-depth research on the nuclear emergency response organization systems, professional team capabilities, and emergency response resource allocation of a typical prefecture-level city and its county-level cities, issues such as incomplete organizational systems, unclear interface relationships, unprofessional talent teams, and imperfect resource allocation have been identified, which affect the effectiveness of emergency response. To address these challenges, a systematic enhancement of nuclear emergency response capabilities in prefecture-level cities was proposed from four aspects: institutional system, core capabilities, team mechanisms, and resource allocation. The perfection of the institutional system is the foundation, the strengthening of core capabilities is the key, and the soundness of team mechanisms is the safeguard. Prefecture-level cities should promote the systematization, specialization, and standardization of nuclear emergency response capability construction with a task-oriented, coordinated, and compatible philosophy and principles, thereby solidifying the cornerstone of China’s nuclear safety.

Objective: To investigate the clinical value of fat attenuation index (FAI) on coronary CT angiography (CCTA) in evaluating the degree of coronary artery stenosis and the diagnostic value of plaque vulnerability. Methods: A total of 80 patients treated for coronary artery diseases from January 2021 to November 2023 were retrospectively included. All patients were diagnosed with non-calcified plaque (NCP) by CCTA examination. Patients were divided according to the severity of luminal stenosis (39 with mild stenosis, 24 with moderate stenosis, and 17 with severe stenosis). According to plaque vulnerability, the patients were divided into a vulnerable plaque group (27 cases) and a non-vulnerable plaque group (53 cases). A Spearman correlation analysis was used to evaluate the correlation between FAI and stenosis severity in patients with NCP, and a multivariate logistic regression analysis was used to explore the factors influencing vulnerable plaques. Results: FAI was significantly lower in the severe stenosis group (−76.95 ± 7.91 HU) than in the mild stenosis group (−66.73 ± 7.69 HU) and the moderate stenosis group (−71.58 ± 8.65 HU), and FAI was significantly lower in the moderate stenosis group than in the mild stenosis group (t = 4.534, 2.190, 4.534, P < 0.05). The correlation analysis showed that FAI was negatively correlated with the severity of coronary artery stenosis (r = −0.726, P < 0.05). There were significant differences between vulnerable and non-vulnerable plaque groups in hypertension [23 (85.19%) vs. 30 (56.60%)], smoking history [8 (29.63%) vs. 4 (7.55)], and FAI (−67.64 ± 8.32 HU vs. −75.69 ± 7.88 HU) (t = 6.535, 6.841, 4.164, P < 0.05). The multivariate logistic regression analysis showed that FAI was a risk factor for vulnerable plaque (odds ratio = 1.439, P < 0.05). Conclusion: FAI can be used to effectively assess the risk stratification of NCP and is of great significance in guiding the clinical management of patients.

Objective: To propose a method for correcting the attenuation of positron emission tomography (PET) data in PET/magnetic resonance (MR) based on transmission scan, and to improve image quality, diagnostic accuracy, and lesion location accuracy. Methods: In this study, the head phantom in the national standard GB/T 18988.1—2013 was used as the experimental model. The head phantom contained three 50 mm diameter cylindrical inserts filled with air, water, and solid teflon. The attenuation correction coefficients were calculated and analyzed based on transmission scan. Results: With slice = 33 and theta = 0, the attenuation correction coefficient was the largest (about 7.5) when the coincidence line passed through the axis of the phantom. The spatial distribution of the attenuation correction coefficients clearly showed the positions of air insert and teflon insert, indicating that the attenuation correction coefficients calculated from transmission scan data were accurate. In the clinical verification experiment, the attenuation correction method based on transmission scan significantly improved the image quality and showed efficient attenuation correction. Conclusion: This paper studied the attenuation correction method for PET data in PET/MR based on transmission scan. This method can improve the image quality. In the future work, the attenuation correction method of PET/MR will be further studied and optimized to facilitate clinical applications.

Objective: To establish testing and evaluation methods for radiation shielding performance of a self-shielded radiotherapy system by measuring the radiation levels around the self-shielded head and neck radiotherapy system. Methods: A total of 14 monitoring points were selected outside the restricted zone of the system. Under radiation conditions from five different fixed directions, an ion chamber survey meter was used to measure and identify the maximum ambient dose equivalent rate at the 14 points. The time-averaged dose rate was then calculated based on the workload. In accordance with relevant radiation protection standards, an instantaneous dose rate of 10 μSv/h and a time-averaged dose rate of 2.0 μSv/h were proposed as the criteria for shielding protection evaluation. Results: Based on the ambient dose equivalent rates at the 14 monitoring points outside the restricted zone, the maximum instantaneous dose rate outside the restricted zone was 7.4 μSv/h. With a workload of 15 patients per day, the maximum time-averaged dose rate was 1.0 μSv/h, which can be used as the criteria for shielding protection evaluation. Conclusion: By considering both instantaneous dose rate and time-averaged dose rate, a comprehensive safety assessment of the radiation shielding performance of a self-shielded radiotherapy system can be conducted.

Objective: With the increase in pet-owning households in China, veterinary clinics have increased at an annual rate of 19.86%. However, the management blind area that may exist in multi-department supervision has led to a significantly worse working environment of radiation workers in veterinary clinics than that of medical institutions. The purpose of this study was to understand the levels of occupational external exposure of radiation workers in veterinary clinics in China, analyze the occupational risks faced by radiation workers in veterinary clinics, contribute to the protection of the occupational health of radiation workers, and provide data and scientific basis for the formulation of national relevant regulations and standards. Methods: The individual dose monitoring data of radiation workers in selected veterinary clinics in 2022 were obtained from the National Individual Dose Registration System. Results: This study involved 1868 radiation workers from 1216 veterinary clinics in 28 provinces and municipalities in China. The maximum annual effective dose was 8.93 mSv, the annual collective dose was 536.77 man·mSv, the average annual effective dose was 0.29 mSv, and the median was 0.15 mSv. The largest proportion of individuals (94.5%) received a dose of less than 1.0 mSv, while 5.4% had doses ranging from 1.0 mSv to less than 5.0 mSv. For radiation workers with an annual effective dose of 1.0 mSv and above, the individual distribution ratio of radiation workers in veterinary clinics was significantly higher compared with those in medical institutions and industrial applications (P < 0.05). Conclusion: The levels of occupational external exposure of radiation workers in veterinary clinics meet the requirements of national standards. However, attention should still be paid to the radiation protection of radiation workers in veterinary clinics. This includes enhancing the responsibility awareness of veterinary clinic owners, strengthening protection training for radiation workers, protecting the occupational health of practitioners, and preventing the occurrence of occupational radiation diseases.

Objective: To analyze the prognosis and influencing factors in patients with radioiodine-refractory differentiated thyroid cancer (RAIR-DTC). Methods: A retrospective analysis was conducted on 52 patients with RAIR-DTC who underwent ineffective ¹³¹I therapy at the Department of Nuclear Medicine, Cancer Hospital, Chinese Academy of Medical Sciences from October 2016 to January 2020. Patients were categorized into progression and stable groups based on disease progression within five years post-treatment. Differences between groups were analyzed using chi-square test and logistic regression. Independent prognostic risk factors were identified using a Cox proportional hazards model. The Kaplan-Meier method with log-rank test was used to evaluate the impact of treatment on the prognosis of the progression group. Results: The 3-year and 5-year survival rates of the 52 patients with RAIR-DTC were 88.5% and 73.1%, respectively. In the progression group, the rates were 81.8% and 57.6%. In the stable group, the rates were 100% and 100%. There were significant differences between the two groups in terms of age, presence of extrathyroidal extension, and the initial ¹³¹I treatment dose (P < 0.05). Univariate analysis indicated that the age, pre-ablation stimulated thyroglobulin level before the first ¹³¹I treatment, the neutrophil-to-lymphocyte ratio before the first treatment, and the sites of recurrence and metastasis were significantly associated with overall survival (P < 0.05). Multivariate analysis showed that age > 55 years (HR=12.40, 95% CI= 2.09-73.57, P=0.001) and distant metastasis (HR=24.47, 95% CI=4.17-143.75, P < 0.001) were independent risk factors for poor prognosis. Kaplan-Meier curve analysis showed that local surgery and/or targeted therapy significantly prolonged progression-free survival in the progression group (P < 0.001). Conclusion: The prognosis for RAIR-DTC is poor, with advanced age and distant metastasis significantly associated with unfavorable outcomes. In elderly patients and those with extrathyroidal invasion, the treatment dose during initial ¹³¹I therapy may be appropriately increased to delay disease progression. For patients with disease progression, prompt local surgical intervention and/or targeted therapy is recommended.

Objective: Ionization chamber detector is commonly used for direct and continuous measurement of tritium concentration in the air. However, the measurement sensitivity is low due to the limitations of weak current measurement technology. It is necessary to develop a proportional counter for measuring tritium in the air. Methods: This study involved the design of a proportional counter, considering various factors such as materials and structure. The stability, plateau curve, detection efficiency, and energy spectrum of the counter were tested. Results: The coefficient of variation of the proportional counter was 3.14%, which met the standard requirement of being less than 15%. The plateau length was 260 V and the plateau slope was 0.80%/100V, which met the requirement of being less than 1%/100V. The tritium detection efficiency reached 68.02%. The energy spectrum measurement indicated a significant difference between tritium signal generated by the proportional counter and background signal, and the distribution of tritium in the energy spectrum was more concentrated. The background counting rate during tritium gas activity measurement could be reduced through energy spectrum measurement. Conclusion: The proportional counter can provide a reference for the direct and continuous measurement of tritium in the air.