Health physics最新文献

Abstract: The exponential diffusion of wearable medical devices (WMD) in recent years has involved people of all ages, including workers. Workers who use WMDs should be considered at a particular risk from electromagnetic fields, and in accordance with EU Directive 2013/35/EU, they require an individual risk assessment. Currently, there is no international standard that provides specific guidance on how to perform such a risk assessment. This paper focuses on the effects of electromagnetic fields on WMDs and does not consider the direct effects on human body tissues. It aims to offer practical recommendations to employers and/or health physicists for the risk assessment of workers with WMDs. Focusing on EU countries, we first describe the requirements outlined by the technical standard for the electromagnetic compatibility (EMC) of medical electrical equipment EN 60601-1-2. Then, some general guidelines on how to perform the risk assessment are provided. The assessment can be conducted by comparing the field values measured in the workplace with the immunity test levels specified in the technical standards of medical electrical equipment. If the measured values are lower than the immunity test levels indicated in the standard and the distance from the electromagnetic source is greater than the distance used by the manufacturer during the EMC (electromagnetic compatibility) tests (typically 30 cm), the risk for the worker may be considered acceptable. However, if the measured values exceed the immunity test levels or the distance criteria, a specific evaluation based on a case-by-case analysis is required.

Abstract: In the widespread use of medical cyclotrons for isotope production, radiological and economic consequences related to the decommissioning of particle accelerators are often neglected. However, decommissioning regulation and its related procedures always demand efforts and costs that can unexpectedly impact on budgets. The magnitude of this impact depends strongly on the residual radioactivity of the accelerator and of the vault, and more specifically on the kind and activity concentration of residual radionuclides. This work reports and discusses a case study that analyzes in detail the characterization activities needed for optimized management of the decommissioning of a medical cyclotron vault. In particular, this paper presents the activities carried out for assessing the activity concentrations and for guiding the disposal of the cyclotron vault of the Italian National Cancer Institute of Milano (INT). An unshielded 17 MeV cyclotron vault was characterized by high resolution gamma-ray spectrometry both in-situ and in-laboratory on extracted samples. Monte Carlo simulations were also carried out to assess the overall distribution of activation in the vault. After a few months from the final shutdown of the accelerator, activity concentrations in the concrete walls due to neutron activation exceeded the clearance levels in many regions, especially close to the cyclotron target. Due to the relatively long half-lives of some radionuclides, a time interval of about 20 y after the end of bombardment is necessary for achieving clearance in some critical positions. Far from the target or in positions shielded by the cyclotron, activation levels were below the clearance level. The comparison between Monte Carlo simulations and experimental results shows a good agreement. The in-situ measurements, simpler and economically advantageous, cannot completely replace the destructive measurements, but they may limit the number of required samples and consequently the decommissioning costs. The methodology described and the results obtained demonstrated that it is possible to obtain accurate estimations of activity concentrations with cheap and quick in-situ measurements if the concentration profile in-depth inside the wall is well known. This profile can be obtained either experimentally or numerically through suitably validated Monte Carlo simulations.

Abstract: Damage to healthy bone following exposure to ionizing radiation has been well documented for at least seven decades. Among the reported effects are a transient increase in stiffness and a reduction in breaking strength. These changes have been linked to a decrease in osteoblast proliferation and differentiation, inducing cell cycle arrest, reducing collagen production, and increasing sensitivity to apoptotic agents. In this work, we analyzed some mechanical and structural changes in compact costal bovine bone (Hereford breed, n = 9) subjected to escalating doses of fast neutrons from a 7 Li(p,n) 7 Be reaction. The mean neutron energy was 233 keV with calculated absorbed doses ranging from 0 to 4.05 ± 10% Gy. Samples were subjected to Young's Modulus (YM) and breaking strength testing with a Universal Testing Machine (UTM). We found an increase in Young's Modulus and a decrease in breaking strength as functions of increasing dose equivalent. Optical coherence tomography (OCT) revealed trabecular displacement into compact bone in an irradiated sample (D = 4.05 ± 10% Gy), with breaching of the endosteal wall. OCT further revealed a "crack-like" structure across the irradiated sample, potentially consistent with damage from a proton track resulting from an elastic (n,p) reaction. No previous report has been found on mechanical changes in large mammalian bones following fast neutron doses, nor of the OCT imaging of such samples.

Abstract: This research examines the cognitive frameworks used by HAZMAT technicians when responding to incidents involving Radiological Dispersal Devices (RDDs), which are conventional explosive devices with radioactive materials incorporated. The objective is to introduce the Expected Mental Model State (EMMS) as a comprehensive evaluation tool for assessing and enhancing the expertise and situational awareness of emergency responders dealing with radiation crises. Through a series of expert focus group sessions using the well-established qualitative methodology of grounded theory, an Expected Mental Model State (EMMS) was developed. The methodology used an influence diagram architecture to conceptually capture and codify key areas relevant to effective emergency response. The research identifies fourteen EMMS key conceptual domains, further elaborated into 301 subtopics, providing a multi-dimensional structure for the proposed mental model framework. Three pivotal notions of mental model emerged within the EMMS framework: Knowledge Topology, Envisioning (Belief), and Response and Operability. These notions were found to align with previous theories of mental models and are vital for understanding how HAZMAT technicians conceptualize and respond to RDD incidents. The study emphasizes the critical role of mental models in enhancing preparedness and effective response strategies during radiation emergencies. The EMMS framework offers a versatile methodology that can be adapted across various kinds of emergency responders and high-risk situations, including the broader Chemical, Biological, Radiological, and Nuclear (CBRN) spectrum. Using this EMMS framework to develop an EMMS Diagnostic Matrix can provide a roadmap for identifying areas for the development of specialized training modules that have the potential to significantly elevate both the quality and efficacy of responder training and preparation.

Abstract: The 210 Pb burden in the skeleton is a measurement value suitable for the estimation of the cumulative exposure to radon, based on which the resultant risk of lung cancer can be derived. There have been a handful of studies that successfully measured 210 Pb activity in the bones of volunteers who had chronic exposure to high concentrations of radon occupationally or in their residences. However, the quantitative relationship between measured 210 Pb activity and radon exposure remains elusive. Herein, we investigate the origin of the skeletal burden by employing the biokinetic model recommended by the International Commission on Radiological Protection and modeling various routes of intake. First, the baseline 210 Pb burden for the general public regarding eating assorted foodstuffs and breathing normal air is obtained. It is found that this baseline burden ranges between 7.3 to 46.5 Bq for a 50-y-old (male) person, which characterizes a large variance due to the uncertainty of each route of intake. Next, we concentrate on radon exposure by referring to two experimental studies where the accounts of exposure and the measured 210 Pb burden for each volunteer are documented in detail. From comparing our prediction and measurements, it is found that exposure to higher concentration of radon is the most significant source of 210 Pb intake, and the quantitative differences can be reasonably explained by the uncertainty resulting from regular intake routes. This study establishes the theoretical foundation for assessing one's risk of lung cancer due to radon exposure by measuring the 210 Pb burden in bones.

Abstract: CAP-88 PC is a commonly used radiological atmospheric dispersion model. This US EPA-approved model is used to demonstrate compliance with atmospheric emission regulations for radionuclides. While the model includes a large library of meteorological data for use across the United States, there are applications when users may wish to use onsite meteorological data as an input to the CAP-88 PC model. Here we present a work-around process for preparing and converting onsite data for use in CAP-88 PC. However, the use of local data should provide a more realistic estimate of doses to members of the public in the immediate vicinity of a facility, although the regulatory agency having jurisdiction may not accept the use of local data for compliance. Additionally, the historical meteorological records from 20+ years ago (at a site many kilometers away) might not be representative of current local weather patterns, highlighting another benefit of using local meteorological data.

Abstract: The primary purpose of this study was to report the mean glandular doses and to determine the national diagnostic reference levels for digital mammography based on data between 2016 and 2018 in China. The data from 19,076 mammograms (4,769 examinations) by random sampling from 118 digital mammography systems were compiled. Exposure factors included age, compressed breast thickness, kVp, mAs, target/filter combination, entrance surface air kerma, and mean glandular doses, which were retrospectively surveyed and recorded from the monitor. The national diagnostic reference levels (75th percentiles) in mean glandular dose were calculated across median value obtained for all included data and stratified to specific compressed breast thickness ranges. The patients' ages ranged from 22 to 88 y, with a median age of 45. The applied voltage and output medians were 28 kVp and 75.1 mAs for all exposure, respectively. The median CBTs were 45 mm and 48 mm for craniocaudal views and mediolateral oblique views, and the corresponding median mean glandular doses were 1.32 mGy and 1.40 mGy, respectively. The national diagnostic reference level at compressed breast thickness of 40-50 mm was 1.67 mGy for CC views and 1.71 mGy for MLO views. The median mean glandular doses varied significantly and increased with compressed breast thickness, demonstrating the necessity of establishing DRL according to breast thickness and optimizing the clinic's digital mammography practice in China.