Radiation protection dosimetry最新文献

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.

The ambient dose equivalent rate H*(10) was determined at various locations in the metropolitan area of the cities of La Paz and El Alto in Bolivia. A NaI(Tl) scintillation detector was employed to infer the gamma-ray fluence, and the fluence was transformed in dose rates by means of the appropriate coefficients. In this paper, a full methodology for the estimation of dose rates associated with gamma rays emitted from the ground (terrestrial radiation) and the atmosphere is developed from measurements made with the scintillator instrument. The energy calibration and resolution of the apparatus are presented, followed by the estimation of its response and efficiency by means of Monte Carlo simulations. Lastly, the definition of H*(10) is used to determine the conversion coefficients needed to transform gamma-ray fluence in dose rates. With this methodology, rates for H*(10) around 123 ± 8 nSv/h were estimated using data collected in three city districts: Mallasa (3320 m a.s.l.), San Antonio (3620 m a.s.l.), and Zona Sur (3400 m a.s.l.). The dose rates are believed to be representative of the terrestrial radiation fields encountered in the highlands of Bolivia.

Objective: To evaluate the radiation dose of chest computed tomography (CT) examinations of pediatric patients and the extent to which volume CT dose index (CTDIvol) underestimates radiation dose in comparison to size specific dose estimates (SSDE).

Methods: Single-center, retrospective study of consecutive unenhanced pediatric (age <18 years) chest CTs between October 2015 and October 2016. Radiation dose as well as demographic and clinical data were recorded from 133 chest CTs. Patients were grouped into 4 categories based on mean effective diameter of the chest. SSDE was generated for each patient according to the water equivalent and effective diameter and compared to CTDIvol. Factors associated with higher radiation doses were assessed.

Results: CTDIvol underestimated radiation dose by 54.7%, 47.6%, 40.2%, and 31.2% (P < .001) for effective diameter groups 1 to 4, respectively, when compared to SSDE (calculated according to the water equivalent). When calculated according to the effective diameter, CTDIvol underestimated radiation dose by 47.6%, 39.4%, 27%, and 12.3% (P < .001) for effective diameter groups 1 to 4, respectively, when compared to SSDE. CT dose parameters, age, weight, Dw, and mean effective diameter were variables associated with higher radiation doses.

Conclusion: CTDIvol systematically underestimated radiation dose in comparison to SSDE in pediatric patients submitted to chest CT and should not be used as the primary parameter to monitor CT protocols in these patients. SSDE calculated according to effective diameter also underestimates the radiation dose compared to SSDE calculated based on water equivalent.

The study aims to evaluate the energy response of the thermoluminescent dosemeter (TLD) CaSO4:Dy from high energy photon beams produced from medical linear accelerator. The test was performed on the polymethyl methacrylate phantom surface and at the depth of dose maximum with a source-to-surface distance of 100 cm and the radiation field size of 12 × 12 cm. The results were compared with the TLD response exposed to 60Co standard source. The results show that the TLD response to the linac's photon differs >30% compared to the TLD response to 60Co exposure when measured at the phantom surface, while at the depth of maximum dose the response is similar (< ±10%), indicating that the TLD response is no longer dependent on the energy. This implies that the current dose reading evaluation based on 60Co calibration curve should be corrected to obtain more accurate dose report of the radiation workers.