Radiation protection dosimetry最新文献

In this article, the submersion dose due to a radioactive cloud of pollutants was evaluated at short downwind distances from an emission stack. The atmospheric transport of contaminants was modelled using the Gaussian plume model (GPM). The algorithm for dose computation and its hypotheses were analysed. Two relevant issues were discussed: the semi-infinite cloud approximation used for pre-calculated dose conversion factors and the lack of a radiation transport model for dose computation outside the radioactive cloud. The GPM-based software HotSpot and GENII V2.10 and a FLUKA Monte Carlo GPM implementation were compared in a scenario characterized by a low release height and two different simplified atmospheric conditions. Compared to FLUKA, HotSpot and GENII V2.10 results showed a significant dose overestimation inside the plume. Moreover, in extremely stable meteorological conditions, only the Monte Carlo code could detect the ground-level dose contribution from an overhead plume.

The present work describes the results for the bilateral comparison between the Secondary Standards Dosimetry Laboratories of the Instituto Nacional de Investigaciones Nucleares (SSDL-ININ), Mexico, and the pilot laboratory, the Centro de Protección e Higiene de las Radiaciones (SSDL-CPHR), Cuba, for the realization of the air kerma (${boldsymbol{K}}_{boldsymbol{a}}$) quantity to: (i) diagnostic X-ray (DXR) IEC 61267:2005 beam qualities: RQR 5 RQR 9, RQT 8, and RQT 9 and (ii) radiation protection (RP) ISO 4037:2019 X-ray beam qualities: N60, N100, and W60, as well S-Cs for gamma radiation. The matched and characterized reference fields are realized at SSDL-ININ with a Toshiba E7252FX X-ray tube. In all cases, the ${boldsymbol{K}}_{boldsymbol{a}}$ measurements are traceable to PTB, except for S-Cs, traceable to ININ. The SSDL-CPHR realizes its reference radiation beam qualities also as matched reference fields with a Pantak HF160C X-ray tube. For the S-Cs beam quality, the CPHR uses a Buchler OB6 irradiator; the ININ, a Siemens Cesagammatron. The transfer ionization chambers calibrated in the RQR and RQT qualities are an Exradin A650/DO70312; for the RQT qualities for CT, a PTW 30009/0655 and RC3CT/9217 were calibrated; and for the RP X-ray qualities, the Exradin A650/DO70312 and a PTW 32002/073 were calibrated. The ratio ${boldsymbol{R}}_{boldsymbol{k}}$ of the resulting calibration coefficients ${boldsymbol{N}}_{{boldsymbol{K}}_{boldsymbol{a}}}$ of each SSDL of the RQR qualities are consistent within the $boldsymbol{U}left(boldsymbol{k}=mathbf{2}right)%$ ≤ 2.3%; for the RQT qualities, the differences are less than the $boldsymbol{U}left(boldsymbol{k}=mathbf{2}right)%$ ≤ 3.6%; and for the RP X-ray qualities, within the order of $boldsymbol{U}left(boldsymbol{k}=mathbf{2}right)%$ ≤ 3.5%. For the S-Cs quality, the ${boldsymbol{R}}_{boldsymbol{k}}$ is in the order of $boldsymbol{U}left(boldsymbol{k}=mathbf{2}right)$ ≤ 3.0%. It should be noted that the ININ U's are generally larger due to the failure of the ${boldsymbol{k}}_{boldsymbol{TP}}$ correction factor, a brief discussion is given here. The ${boldsymbol{E}}_{boldsymbol{n}}$ score from ISO 17043 provides statistical support to this comparison.

Environmental measurements of Radon and its progeny were carried out in a gold mining area in the department of Antioquia, Colombia. Radon concentration measurements were carried out during 2 y in seven different measurement points in three types of geological zones, by using EPERM electret chambers and DOSEman Pro detectors at each point. Radon concentration values between 858 ± 59 Bq m-3 and 2469 ± 158 Bq m-3 and an equilibrium factor between 0.15 and 0.27 were found. The annual effective dose, taking into account the radon concentration, was determined under two calculation methodologies ([1] and International Commission of Radiological Protection 137), obtaining values of up to 7.7 mSv, and 13.5 mSv, respectively, for 2000 annual working hours, which shows the importance of the dosimetric data and epidemiological studies carried out year after year to reduce the uncertainties regarding estimates of radon exposure and the need to carry out individual monitoring of miners.

Introduction: Bitewing examinations are used to examine the pediatric dental status. The aim of this study was to compare the image quality and radiation dose between two different X-ray systems used for pediatric bitewing imaging.

Materials and methods: Data were obtained from both pediatric in vivo bitewing studies and phantom studies. Two X-ray systems were used: Trophy CCX digital (TCCX) (Trophy Irix 70, Marne-la-Vallee, France) and Planmeca Pro X (PPX) (Planmeca, Helsinki, Finland). An Unfors dosimeter (Unfors EDD-30, Billdal, Sweden) was used to measure the skin dose. Image quality was evaluated blindly by three experienced dentists using a Likert scale of 1-5 based on the visual representation of the anatomical structures with emphasis on caries.

Results: The highest scoring in vivo bitewing images were obtained with TCCX, but the skin dose was 36% higher (mean 3029 ± 613 μGy) and 113% higher (mean 1364 ± 276 μGy) with standard settings than with compared to PPX. The evaluation of image quality revealed a higher median value for all ratings of TCCX compared to PPX for both the patient and phantom studies, meaning that the images of TCCX were rated as higher quality than the images from PPX. No correlation was found between the median score and the skin dose or between the median score and the exposure times.

Conclusion: A significant difference in radiation dose and image quality was found between TCCX and PPX in bitewing imaging. TCCX generally produced higher doses and better graded images, although all images were suitable for diagnosis.

This study assesses the radiological risks associated with phosphate fertilizer application on farmlands in Ondo State, Nigeria. Soil samples from ten agricultural towns were analyzed for radionuclide concentrations using gamma-ray spectrometry. Primordial radionuclides such as 238U, 232Th, and 40K were examined, with 40K showing the highest concentration due to the potassium-rich nature of phosphate fertilizers. Spatial variability in radionuclide concentrations was observed, attributed to agricultural activities. Despite variations, mean activity concentrations were below global averages, indicating low radiological risks. Hazard indices, radium equivalent concentrations, and absorbed dose rates were all within safe limits. The annual effective dose equivalent was significantly lower than recommended levels, and excess lifetime cancer risk estimates were below the global average. The study emphasizes the importance of educating farmers on the potential adverse effects of radionuclides and recommends reducing the use of inorganic fertilizers to promote eco-friendly agricultural practices.

This study proposes a practical approach to assessing the need for and determining the transitioning parameters from age-specific to size-specific dose protocols in paediatric head computed tomography examinations. It was designed to begin with the two different age-specific protocols currently applied on paediatric patients of 1 y ≤ age ≤ 6 y (21.34 mGy) and those of age >6 y (34.73 mGy). One characteristic size (HDthreshold) was found by measuring anteroposterior head diameter on historical topograms and used with age to set 135 cases into four groups for investigation (A, ≤6y, ≤HDthreshold; B, ≤6y, >HDthreshold; C, >6y, ≤HDthreshold; and D, >6 y, >HDthreshold). The image quality was compared in both subjective and objective manners. Results suggest patients in Group C may have received a potential overdose (38%), while the exposure setting for Group D may replace that for B. The proposed strategy was sufficient to assess the necessity and determine the transitioning parameters from age- to size-specific dose protocols.

Chronic inhalation intake of radionuclides is possible for radiation workers in the nuclear industry. The International Commission on Radiological Protection (ICRP) provides organ retention fractions as well as daily urinary and fecal excretion for chronic intake of various radionuclides. In this study, organ retention fractions and daily urinary excretion for chronic intake were estimated for constant chronic intake (CCI) and realistic chronic intake (RCI) scenarios. CCI is a daily intake of 1 Bq, and RCI is an intake of 1.4 Bq for five working days followed by two days gap. Radiologically important radionuclides such as 239Pu, 60Co, 137Cs, 131I, and 3H having long, moderate, and short effective half-lives in the deposited organ or whole body were considered. The retention fractions and daily urinary excretion of all the radionuclides studied for RCI were found to converge with those for the CCI scenario at ~40 to 200 days except for daily urinary excretion of 131I.

In this paper, the effect of thyroid collars on radiation dose during dental cone-beam computed tomography (CBCT) was evaluated using Monte Carlo simulations and to calculate the effective dose underestimated for the actual CBCT examination due to accounting only for the head and neck. Three thyroid collar models that covered the surface of the phantom were established according to the International Commission on Radiological Protection (ICRP) adult-male mesh-type reference computational phantoms, and a Particle and Heavy Ion Transport code System was used to calculate the equivalent and effective doses of ICRP phantom when different thyroid shielding protocols were used in NewTom VGi evo CBCT, considering one medium (12 × 8 cm) and one small (8 × 5 cm) fields of view (FOVs), and two centre positions were used for each FOV. In four CBCT scanning scenarios, thyroid shielding reduced the equivalent dose for many tissues. The results indicate that the portion of the thyroid collar that wraps around the neck has the main role in reducing the effective dose during dental CBCT examinations, and the higher the axial level of the top of the shielding, the better the effectiveness of the shielding. In this study, the underestimation of the effective dose due to considering only the head and neck was 3.1%-8.1%, and the underestimation was more pronounced in larger FOVs.

This work assessed the activity concentrations of 238U(226Ra), 232Th, and 40K and their associated radiological risks due to exposure to soil and consumption of food crops in Babban Tsauni artisanal gold mine, Gwagwalada, Nigeria, using the gamma spectrometry technique. The mean activity concentrations of 226Ra, 232Th, and 40K in the mine soil were 60.2 ± 9.9, 161.4 ± 16.2, and 664.6 ± 138.2, while they were 46.4 ± 4.9, 79.9 ± 39.3, 266.4 ± 185.4 for tubers and 46.9 ± 15.7, 100.5 ± 35.8, 311.4 ± 132.7 (Bq/kg) for grains, respectively. The results reveal that the activity concentrations of radionuclides in all samples exceeded the recommended values set by United Nations Scientific Committee on the Effects of Atomic Radiation (33, 45, and 420 Bq/kg) except 40K, which fell within the acceptable limit in all food crop sample types. Estimated results for radiological hazard parameters, radium equivalent, annual effective dose due to ingestion, and excess life cancer risk were within safe limits, while the annual effective dose due to external gamma radiation in soil and annual gonadal equivalent dose were significantly high in all investigated samples; these call for constant radiological monitoring.