Health physics最新文献

This study aims to assess the residual radioactivity produced in the human head phantom following irradiation from a boron neutron capture therapy neutron source based on a 2.8 MeV proton accelerator. Using Monte Carlo software to simulate irradiation on a head phantom based on ICRP Publication 110, it was found that, in addition to the nuclides 24 Na, 38 Cl, and 42 K reported in other literature, 32 P is the nuclide that contributes the most to the internal exposure dose in patients post-BNCT. Calculations indicate that the effective dose resulting from 60 min of irradiation activation ranges between 148 and 401 μSv, which is relatively low. This study also analyzed the dose rate at a distance of 60 cm from the activated head. Approximately 5 min after irradiation ends, short-lived nuclides such as 19 O and 20 F decay completely, reducing the dose rate to below 1 μSv h -1 . Although nuclides like 24 Na will continue to emit radiation, the dose rate remains at a safe level.

Iodine-131 ( 131 I) has been used widely in diagnosing and treating thyroid disorders, but its radioactive nature poses risks of gamma radiation exposure to those near the patient. To mitigate this, radiation protection measures are needed, among which is the provision of optimal structural shielding. In the Philippines, achieving this involves using minimum shielding thickness to meet safety limits from national regulations. Widely used conventional methods, like those based on the tenth-value layer (TVLs) measurements, may yield poor estimates, while computational simulations are precise but impractical to use due to their complexity. Archer's fitting method offers a simple and accurate alternative for designing optimal shielding in medical imaging and radiotherapy facilities based on multiple studies. However, little to no data is available regarding the use of Archer's fitting method in providing better accuracy in shielding calculations in isolation rooms of 131 I therapy facilities. A comparison of the transmission factors calculated using different calculation methods was done, and their effect on the minimum shielding thicknesses was investigated. Transmission curves generated with broad-beam TVLs reported from previous studies yielded the closest agreement with ANS/ANSI 6.4.3 buildup factors for lead barriers. On the other hand, results showed the closest agreement among the transmission curves and shielding thicknesses acquired with the American National Standard (ANSI/ANS) 6.4.3. buildup factors, Archer's fitting method, and Monte Carlo simulation through Particle Heavy Ion Transport System (PHITS) ver. 3.28 code for ordinary concrete barriers. Poor agreement was seen with the curves generated with the Narrow-Beam and Ideal Broad Beam TVL methods and the curve generated with ANSI/ANS 6.4.3. buildup factor data. Broad-Beam TVLs from previous studies, Monte Carlo Simulation, and Archer's fit can be alternative options for shielding design. An experimental study is proposed for verification.

To characterize awareness of radiation-related knowledge (RRK) and nuclear energy-related knowledge (NERK) among students and teachers living and working around nuclear power plants (NPPs), a survey of 546 teachers and students in two schools (one middle school and one high school) within 30 km of an NPP in Liaoning Province was conducted via paper questionnaires, web-based surveys, and face-to-face interviews. The data were entered using EpiData 3.1, and the result was analyzed using R Version 3.2.2. The analytical methods used included utilization and composition ratios, as well as mean-χ ± SD to statistically describe the data, and χ2 (Fisher's and Pearson's tests) as well as Student's t -test to draw comparisons. The results showed that the RRK and NERK scores (14 questions in total) of the teachers and students (546 individuals in total) were 75.6% and 57.4%, respectively. In the radiation knowledge section of the survey, the RRK of the students plus teachers was 67.8%, while the NERK score was 55.9%. The teachers' attitudes toward the benefits of nuclear energy was more positive, which may be attributable to their higher educational levels, their occupations, or their backgrounds. The survey results also indicated that teachers and students trusted nuclear science experts and authoritative media more than other non-authoritative media. This indicates that the ways in which relevant knowledge related to nuclear energy is disseminated should be carefully considered.

The aim of this study was to evaluate the radiological risk to the public due to the use of wood ash as a fertilizer in gardens. Dose assessment is a process in radiation protection that involves determining the amount of radiation to which a person or population has been exposed. It helps to evaluate potential health risks more effectively to ensure that radiation exposure remains within safe limits. Three pathways were considered: inhalation of ash, ingestion of locally produced food fertilized with ash, and direct ingestion of ash. It was assumed that a 0.01 cm, 0.5 cm, or 1-cm-thick layer of ash is used for fertilization per year and that half of the vegetables consumed annually come from one's own garden. The dose assessment for a member of the public older than 17 y using the highest concentrations of 137Cs and 90Sr measured in 27 wood (logs, chips, briquettes, and pellets) ash samples and fertilization with 0.01 cm of ash results in a calculated dose of 3.02 ± 0.24 μSv y-1. The primary exposure pathway is the ingestion of locally produced foods fertilized with wood ash. Besides radionuclides, ash also contains concentrated non-combustible components, including potentially harmful minerals, salts, heavy metals, and organic pollutants. These substances are found in particularly higher concentrations in ash from wood pellets and briquettes than in log and chip ash, so its use as fertilizer---especially in vegetable gardens---should be carefully considered.

In recent years, consumer-grade electronic radon monitors (ERMs) have become increasingly popular for measuring radon in residences and public buildings. Many of these devices are designed for use by the general public, with features and price points that make them accessible alternatives to passive detection methods such as alpha track detectors. However, the influx of new devices into the market and the absence of independent performance evaluations have raised concerns about the reliability of manufacturer claims. This study evaluated the performance of 15 different consumer-grade ERMs at prices less than $400 Canadian (CAD) and which were readily available through online marketplaces under radon exposure conditions ranging from 110 to 2,400 Bq m -3 . Short-term (2- to 3-wk) tests were conducted in radon chambers at Health Canada and Radiation Safety Institute of Canada facilities. Long-term (13-wk) tests were conducted at the underground low-background counting room at SNOLAB. Testing revealed two distinct groups of high- and low-performance ERMs, with absolute mean differences (AMDs) either less than 22% or ranging from 28-238%, compared to reference devices. Long-term testing showed that most ERMs demonstrated improved accuracy with prolonged exposures. This study also highlights the impact of several environmental and technical factors on ERM performance and emphasizes the need to consider performance indicators beyond accuracy. These findings underscore the critical need for independent third-party testing to validate the performance of ERMs, alongside the establishment of robust standards and regulatory frameworks to ensure the reliability of radon measurements, protect public health, and foster consumer confidence.

Computed tomography (CT) imaging is an essential tool for diagnostic purposes but exposes patients, including those who are pregnant, to ionizing radiation, potentially impacting fetal health. Accurate dose estimation is necessary to manage these risks effectively. This study aimed to determine conversion factors for effective dose and uterus dose for CT imaging in pregnant patients, adjusted for gestational stages and various scan regions. The National Cancer Institute dosimetry system for computed tomography (NCICT) simulated photon interactions in hybrid phantoms representing pregnant patients at different gestational stages. A CT scanner model was used across eight gestational stages and for seven different scan regions. Dose length product, effective dose, and uterus dose values were recorded, and conversion factors were calculated for estimating effective dose and fetus dose. The study generated gestational age-specific conversion factors, which varied based on CT scan region. The results reveal a reduction in radiation dose with advancing gestational age, particularly in abdomen and pelvis scans, emphasizing the importance of gestation-specific dose adjustments. The study offers valuable conversion factors for improved radiation dose management in pregnant patients, reducing unnecessary exposure risks, and improving diagnostic practices in CT imaging.

L-band in vivo electron paramagnetic resonance (EPR) tooth dosimetry is a rapid, non-invasive method for determining the ionizing radiation dose of individuals. Tooth positioning and geometry are the dominant factors influencing EPR intensity. However, the delineation of the geometric parameters and their influence on EPR intensity is still unclear. This induces limitations in the availability of dosimetry for triage and leads to the imperfect consideration of geometric variations affecting EPR intensity. This study aimed to analyze the dosimetric sensitivity variations for each geometric parameter separately. Using finite element analysis, model-based parametric analyses were performed on five geometric parameters: labial enamel thickness (τlab), enamel area (Aen), aspect ratio (RA), horizontal curvature (CH), and vertical curvature (CV). The distributions of these parameters were investigated using micro-CT images from 12 human maxillary central incisors. A quasi-tooth model was proposed to mimic the tooth geometry based on the geometric parameters. The quasi-tooth model well simulated the sensitivity variations observed in the micro-CT derived tooth model. The sensitivity showed a strong linear correlation with the three geometric parameters (τlab, CH, and CV), whereas Aen exhibited a plateau around its average value (75 mm2), and no clear trend was observed for RA. After normalization, τlab, CH, and CV were identified as the dominant contributors to sensitivity variations, whereas Aen and RA had less influence. Considering the correlation between τlab and Aen (r = 0.67, p = 0.017), previous geometric correction methods using Aen may have accounted not only for the direct influence of Aen but also for the indirect correction of τlab. These results demonstrate the principles and limitations of previous geometric correction methods and imply the need for an enhanced method that incorporates multiple parameters for L-band in vivo EPR tooth dosimetry.

Introduction: Medical workers account for about 75% of all workers exposed to ionizing radiation; therefore, occupational radiation protection is still a challenge in clinical practices and, consequently, measures should be put in place to optimize radiation in clinical practice.

Objective: The aim of this study was to assess the occupational radiation dose for staff in some selected radiology departments in Ghana as a precursor for optimization studies.

Methods: A total of 68 occupationally exposed workers (OEWs) radiation dose history for 5 facilities have been analyzed. This study is a retrospective study that involves the assessment of the dose records of occupational exposed workers in five radiology departments in the Greater Accra region of Ghana from the Radiation Protection Institute of the Ghana Atomic Energy Commission (GAEC) dose records history. The OEWs included in the study were radiographers/technologists, radiologist, physicians, medical physicists, and nurses. These records were collected and assessed for a period of 5 years (2019-2023). TLDs are worn under the lead aprons to estimate Hp (10) or deep dose and on aprons for Hp (0.07) or skin dose.

Results: A total of 68 OEWs' dose histories for 5 facilities have been analyzed. It was observed that the average annual effective dose for all workers throughout the study period ranged from 0.29 ± 0.07 mSv to 0.41 ± 0.05 mSv. The variations in the mean annual dose for the OEWs for the facilities in the study could be due to the number of OEWs that were monitored and the type and quantity of equipment at the facility during the year under review.

Conclusion: The occupational radiation dose for OEWs in some selected radiological departments in Ghana have been evaluated. The facility with the highest number of OEWs recorded relatively higher mean annual effective dose. The annual effective doses were lesser than the yearly occupational dose limit of 20 mSv as recommended by national and international guidelines.