Health physics最新文献

Background: A nationwide survey of x-ray imaging practices was conducted during 2014-2015 of a representative sample of US dental offices to gather data regarding patient exam frequencies, indicators for radiation dosimetry and related imaging data, and the data were compared to similar studies conducted during 1993 and 1999.

Purpose: The survey results are compared with prior surveys to observe trends in the state of dental x-ray practice, particularly with regard to the use of digital imaging technologies, including cone-beam computed tomography. A total of 199 dental offices were visited in 25 participating states, and comprehensive radiological data were gathered regarding intraoral, panoramic, and cone-beam CT imaging practices. Data were also gathered regarding pediatric x-ray imaging practices. State radiation control data registries of dental offices were combined with gathered survey data to infer total US annual exam and per-capita exam volumes for all three imaging modalities. The clinical applications of imaging modalities in dentistry are not studied in this paper.

Results: The number of intraoral x-ray exams performed annually in the US increased from approximately 191 million exams during 1993 to 296 million exams in 2014-2015. The per-capita rate also increased from 74 to 93 exams per 100 persons during the same period. The annual number of panoramic exams more than doubled from 11 million in 1993 to 21 million in 2014-2015. An estimated 3.5 million CBCT exams were conducted in dental offices in the US during 2014-2015, including 1.1 million exams on children and adolescents. Radiation dose from intraoral imaging decreased notably between 1993 and the most recent study in 2014-2015, from 1.9 mGy to 0.9 mGy.

Conclusion: The total US exam volume and per-capita exam rates for intraoral imaging have increased from 1993 to 1999; however, patient radiation dose (as measured by skin-entrance air kerma, Ka,e) decreased substantially. A major contributor to that observed reduction in radiation dose is the now-prevalent use of digital imaging methods for intraoral radiography.

Radon ( 222 Rn) is a naturally occurring radioactive gas and a significant cause of lung cancer globally, second only to inhaled tobacco smoke. This review examines radon exposure in Japan, its public health risks, current regulations, and mitigation strategies in the context of international standards. Studies show that Japan's indoor radon concentrations average around 15 Bq m -3 , significantly lower than the global mean of approximately 40 Bq m -3 . Furthermore, only a small percentage, estimated at 0.1 to 1%, of Japanese homes exceed the World Health Organization's reference level of 100 Bq m -3 . As a result, radon is responsible for a smaller proportion of lung cancer cases in Japan, around 4%, compared to many Western countries. Nonetheless, radon remains an important public health concern, especially as modern homes become more airtight, potentially elevating indoor radon levels. The review also explores the geographic distribution of radon in Japan, highlighting regions (e.g., parts of western Japan with granitic bedrock) that exhibit higher natural radioactivity. It assesses the absence of a comprehensive national radon regulation in Japan, contrasting it with numerous countries that have established reference levels, building codes, and action plans. This review discusses effective radon mitigation techniques, including active soil depressurization and improved ventilation, applicable to Japan's building context. It argues for a proactive national radon policy to promote routine monitoring, public awareness, and remediation of high-radon homes. Finally, it proposes forming an association of radon scientists and technologists in Japan to enhance research, training, and policy advocacy.

High concentrations of radon may cause radiation damage to the human body. Finding the biomarkers of radon-induced radiation damage is particularly important for the research and treatment of radon-induced lung cancer. In this study, the expression of γH2AX protein in peripheral blood lymphocytes of miners exposed to high concentrations of radon was detected by flow cytometry. To investigate the possible damage in peripheral blood lymphocytes of miners under a high radon environment, a microRNA (miRNA) microarray technique was used to screen the differentially expressed miRNAs in the peripheral plasma of miners exposed to different concentrations of radon. Prediction of the target genes and the possible biological functions of differentially expressed miRNAs in the peripheral plasma of miners was performed. The results indicated that the relative expression level of γH2AX protein in peripheral blood lymphocytes of miners was significantly higher than that of the control group ( P <  0.05). Bioinformatics methods were used to predict the differential expression miRNA chip to screen the target genes of differentially expressed miRNAs and the signaling pathways that may be involved in screening differentially expressed miRNA target genes and to investigate the relationship between some different miRNA target genes and cellular pathways. The analysis of the cellular pathways predicted by differentially expressed miRNAs, including the process of cell cycle, provides new information for the study of miRNAs as potential biomarkers of radon-induced radiation damage in peripheral blood.

The computerized tomography scanners play a significant role in the radiotherapy treatment planning process. The electron density obtained from the CT-RED curve can be used to determine the structure of materials, and TPS calculates the dose based on the material's composition. Errors in this curve can lead to inaccuracies in dose estimation, particularly in heterogeneous tissues. In this study, the effect of variations in the CT-RED curve on the radiation dose calculated with different algorithms was also investigated. A virtual phantom was created by the TPS system for five different environments, including two low-density (HU:-750 and HU:-300) and two high-density (HU:750 and HU:300) materials. Four different erroneous CT-RED curves were created, representing -5%, -10%, +5%, and + 10% deviations from the original CT-RED curve. The positive deviations are more prominent in regions with low HU values. On the other hand, negative errors tend to be more noticeable in regions with higher HU values. This indicates that changes in dose discrepancies are not proportional to the variations in HU. Since the HU values are converted to RED by the TPS, inconsistencies in HU values may lead to errors in the dose calculated by TPS. It is evident that errors in the CT-RED curve can affect the dose calculated by the TPS. However, it appears that this effect remains within acceptable limits. Given that different errors can combine to create significant differences, it is crucial not to overlook the importance of accurately transferring the CT-RED curve to the TPS.