Health physics最新文献

Abstract: In this study, the occupational radiation dose, radon gas, and non-ionizing radiation doses originating from electromagnetic fields (EMF) to which radiation workers are exposed were monitored and evaluated for 1 y. Using electronic personnel dosimeters (EPD), average daily radiation doses based on the number of patients and annual average effective dose results of radiation workers were obtained over a period of 1 y. Also, the annual effective dose and risk values were calculated for 8 h and 24 h by taking radon gas measurements at 2-mo intervals in the nuclear medicine department. Finally, electric field measurements were made one day a week in the selected areas. All the results obtained were compared with national and international dose limits. The results obtained as a result of EPD, radon gas, and EMF measurements made in the nuclear medicine department were found to be far below the international and national legal dose limits.

Abstract: In reviewing a video series that they created for the website of the Health Physics Society (HPS), past leaders of the Health Physics Society have treated as authoritative and trustworthy the scientific misconduct theories of University of Massachusetts Professor Edward Calabrese. No mention is made of detailed critiques of Calabrese's work. I show that Calabrese's historical work as presented by HPS's authors is unreliable because it overlooks key historical text and key statistical concepts about the limits of an early atomic bomb genetics study. When these errors are corrected, claims of scientific misconduct on the part of historical figures evaporate. Claims of threshold behavior in early radiation genetic experiments are wrong for atomic bomb data. Calabrese's unique claims about thresholds in early animal genetic data are not credible for human cancer, given the doses at which they were carried out (>30 R). Recent epidemiological studies of both acute and protracted exposure in humans fail to show dose-rate effects or a dose threshold above 30 R. Such results from human data should be more relevant for most regulators and review committees than Calabrese's claims about old data on animals. Disclaimers, errata, and links to critiques should be added to the HPS webpage hosting the 22-part video series. Failure to do so can cause damage to reputations and historical accuracy because it erroneously validates Calabrese's inflammatory claims of scientific misconduct against past scientists, including three Nobel Prize winners, members of the NAS, and presidents of the AAAS.

Abstract: We developed a statistical theory of zero-count-detector (ZCD), which is defined as a zero-class Poisson under conditions outlined in this paper. ZCD is often encountered in the studies of rare events in physics, health physics, and many other fields where counting of events occurs. We found no acceptable solution to ZCD in classical statistics and affirmed the need for the Bayesian statistics. Several uniform and reference priors were studied, and we derived Bayesian posteriors, point estimates, and upper limits. It was shown that the maximum-entropy prior, containing the most information, resulted in the smallest bias and the lowest risk, making it the most admissible and acceptable among the priors studied. We also investigated application of zero-inflated Poisson and Negative-binomial distributions to ZCD. It was shown using Bayesian marginalization that, under limited information, these distributions reduce to the Poisson distribution.

Abstract: Objectives: To analyze the effects of normal x-ray inspection, machine washing, and machine drying on thermoluminescent dosimeter (TLD) measurements during external individual monitoring and to provide suggestions for determining individual monitoring measurements under the mentioned abnormal situations. In this study, we focused on three abnormal situations: x-ray inspection, machine washing, and machine drying, which are common in external individual dose monitoring. We measured and compared the doses from TLD with and without 11, 23, 35, and 50 security checks. We used different radiation sources to expose the TLDs before or after machine washing with or without hot drying. The three radiation sources are natural background radiation, 137 Cs γ rays, and 320 kVp x-rays. We measured 20 TLDs for each situation. The average doses for the TLDs with 11, 23, 35, 50 security checks are 27.7 μGy, 59.7 μGy, 84.1 μGy, and 121.0 μGy, respectively. We measured an average dose of 2.5 μGy per exposure. The doses showed no significant difference between different times of washing with different radiation sources, natural background radiation, 137 Cs, or x-ray exposures. There was also no significant difference between the dose coming from the controlled group, drying at 60 °C and 90 °C for 1 h after exposure to 137 Cs γ rays and 320 kVp x-rays. The common machine drying under the temperature of 90 °C did not affect TLD measured doses.

Abstract: This study investigated indoor radon concentrations in modern residential buildings in the Cold Area and Severe Cold Area in China. A total of 19 cities covering 16 provinces were selected with 1,610 dwellings measured for indoor radon concentration. The arithmetic mean and geometric mean of indoor radon concentration were 68 Bq m -3 and 57 Bq m -3 , respectively. It was found that indoor radon concentrations were much higher in the Severe Cold Area than those in the Cold Area. The indoor radon concentrations showed an increasing trend for newly constructed buildings. It was estimated that the average effective dose from inhalation of indoor radon is 2.15 mSv and 1.60 mSv for the Severe Cold Area and Cold Area, respectively. The more and more rigid energy-saving design for residential buildings in the Severe Cold Area and Cold Area has an obvious impact on the increased trend of indoor radon due to extremely low air exchange rate in China.

Abstract: Institutional radiation safety committees review research studies with radiation exposure. However, ensuring that the potential patient benefit and knowledge gained merit the radiation risks involved often necessitates revisions that inadvertently delay protocol activations. This quality-improvement study analyzed protocols, identified factors associated with approval time by a radiation safety committee, and developed guidelines to expedite reviews without compromising quality. Clinical protocols submitted to the University of Pennsylvania's Radiation Research Safety Committee (RRSC) for review between 2017 and 2021 were studied. Protocol characteristics, review outcome, stipulations, and approval times were summarized. Statistical analysis (Spearman's rho) was used to investigate stipulations and approval time; rank-sum analysis (Kruskal-Wallis or Wilcoxon) was used to determine whether approval time differed by protocol characteristics. One hundred ten (110) protocols were analyzed. Approximately two-thirds of protocols used approved radiopharmaceuticals to aid investigational therapy trials. Twenty-three percent (23%) of protocols received RRSC approval, and 73% had approval withheld with stipulations, which included requests for edits or additional information. Submissions had a median of three stipulations. Median and mean RRSC approval times were 62 and 80.1 d, and 41% of protocols received RRSC approval after IRB approval. RRSC approval time was positively correlated with stipulations (Spearman's rho = 0. 632, p < 0.001). RRSC approval time was longer for studies using investigational new drugs (median 80 d) than approved radiopharmaceuticals (median 57 d, p = 0.05). The review process is lengthy and may benefit from changes, including publishing standardized radiation safety language and commonly required documents and encouraging timely response to stipulations.

Abstract: Uranium is naturally occurring in groundwater used for drinking; however, health risks from naturally occurring concentrations are uncertain. Uranium can cause both radiological and chemical toxicity following ingestion. Bladder and kidneys receive a dose when uranium is excreted into the urine. Investigate the association between uranium in drinking water and bladder cancer risk in a case-control study. A population-based bladder cancer case-control study was conducted in 11 counties of southeastern Michigan. A total of 411 cases and 566 controls provided drinking water and toenail samples and answered questions about lifestyle and residential history. Uranium was measured in drinking water and toenails, and its association with bladder cancer was assessed via unconditional logistic regression models. Median uranium concentration in water was 0.12 μg L -1 , with a maximum of 4.99 μg L -1 , and median uranium concentration in toenails was 0.0031 μg g -1 . In adjusted regression models, there was a suggestion of a protective effect among those exposed to the upper quartile of uranium in drinking water (HR = 0.64, 95% CI: 0.43, 0.96) and toenails (HR 0.66; 95% CI 0.45, 0.96) compared to those in the lowest quartile. Our objective is to investigate additional adjustment of drinking water source at home residence at time of recruitment to address potential selection bias and confounding attenuated results toward the null for drinking water uranium (HR = 0.68, 95% CI: 0.44, 1.05) and toenail uranium (HR = 0.80, 95% CI: 0.53, 1.20). This case-control study showed no increased risk of bladder cancer associated with uranium found in drinking water or toenails.

Abstract: US Department of Energy national laboratories can play an integral role in not only the advancement of science but also in the treatment of various medical conditions through research and development activities conducted at radioisotope production facilities. A project has been underway at Oak Ridge National Laboratory since 2016 whose mission is to produce and supply the radioisotope 227 Ac, which is used in a radiopharmaceutical developed to treat certain types of prostate cancer and bone metastases. Production activities result in the environmental release of airborne radioactive emissions, which are governed by Clean Air Act regulations described in 40 CFR Part 61, Subpart H. Stack 3039, the source that emits radioactive effluents from 227 Ac production, is subject to additional requirements outlined in American National Standards Institute (ANSI) N13.1-1969 due to its grandfathered status. Radioactive emissions are limited to levels below those that would cause annual compliance dose standards for members of the public to be exceeded and stack 3039 to lose its grandfathered status. To allow for maximum production of 227 Ac without exceeding relevant dose limits, monthly tracking of project emissions and resulting CAP88-PC modeled effective doses to a maximally exposed individual have been implemented. Four years of tracking data were compiled and analyzed to identify additional methods that could be used to estimate project doses more frequently, potentially further optimizing 227 Ac production while maintaining compliance with applicable regulations.

Abstract: The ICRP 2011 Seoul Statement recommended a reduction in the dose limit for lens exposure to 100 mSv for 5 y and 50 mSv for 1 y. Based on this recommendation, the dose limit for lens exposure was lowered in Japan with the revision of the Ionization Regulations, which took effect in April 2021. In the present study, lens doses were measured during fluoroscopic procedures performed in four departments (Urology, Pediatrics, Gastroenterology, and Orthopedics). Lens doses were measured without protective eyewear for 6 mo (pre-intervention) and then with protective eyewear for the next 6 mo (post-intervention). Monthly doses were collected and lens doses before and after the use of protective eyewear were calculated as the lens dose per unit time. The use of protective eyewear reduced the lens dose per unit time by approximately two thirds. In all departments, the lens dose was slightly lower after than before the intervention. A significant difference was observed in lens doses between the pre- and post-intervention periods in the Urology department. The present results demonstrated the effectiveness of protective eyewear in daily practice. Therefore, the use of protective eyewear is recommended during fluoroscopic procedures.

Abstract: An electret detector is a piece of dielectric material film charged or polarized by a specific charging method to induce a quasi-permanent electric field. Electret films perform unique characteristics for production and applications in many areas of science and technology, especially in health physics dosimetry. A charged electret detector, when placed in an ionized environment, collects negative or positive ions depending on its original charging state, which reduces its original charge. The number of charges reduced in the ionized field is usually proportional to the absorbed radiation dose. In this paper, the state-of-the-art information on the type of electrets, production methods, some applications in particular in health physics dosimetry, and relevant concepts are reviewed.