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Chest computed tomography (CT) plays a vital role in the early diagnosis, treatment, and follow-up of COVID-19 pneumonia during the pandemic. However, this raises concerns about excessive exposure to ionizing radiation. This study aimed to survey radiation doses in low-dose chest CT (LDCT) and ultra-low-dose chest CT (ULD) protocols used for imaging COVID-19 pneumonia relative to standard CT (STD) protocols so that the best possible practice and dose reduction techniques could be recommended. A total of 564 articles were identified by searching major scientific databases, including ISI Web of Science, Scopus, and PubMed. After evaluating the content and applying the inclusion criteria to technical factors and radiation dose metrics relevant to the LDCT protocols used for imaging COVID-19 patients, data from ten articles were extracted and analyzed. Technique factors that affect the application of LDCT and ULD are discussed, including tube current (mA), peak tube voltage (kVp), pitch factor, and iterative reconstruction (IR) algorithms. The CTDIvol values for the STD, LDCT, and ULD chest CT protocols ranged from 2.79-13.2 mGy, 0.90-4.40 mGy, and 0.20-0.28 mGy, respectively. The effective dose (ED) values for STD, LDCT, and ULD chest CT protocols ranged from 1.66-6.60 mSv, 0.50-0.80 mGy, and 0.39-0.64 mSv, respectively. Compared with the standard (STD), LDCT reduced the dose reduction by a factor of 2-4, whereas ULD reduced the dose reduction by a factor of 8-13. These dose reductions were achieved by applying scan parameters and techniques such as iterative reconstructions, ultra-long pitches, and fast spectral shaping with a tin filter. Using LDCT, the cumulative radiation dose of serial CT examinations during the acute period of COVID-19 may have been inferior or equivalent to that of conventional CT.

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Herein, we evaluated the neutron and gamma capture dose equivalent rates at the maze entrance of Varian TrueBeam and Elekta Versa HD™ medical linear accelerators (linacs) using experimental measurements as well as empirical calculations. Dose rates were measured using calibrated neutron and gamma area survey meters placed side-by-side at the measurement point of interest. Measurements were performed at a source-to-detector distance of 100 cm, with a 10 × 10 cm2 field size therapeutic X-ray beam, and a 30 × 30 × 15 cm3 solid water patient equivalent phantom, with a linac operating at 15, 10 MV, and 10 MV flattened filter-free (FFF). Dose rates were also measured at different points at the centerline along the maze towards the maze entrance. The measured dose equivalent rates at the maze entrance were comparable to those reported in the literature. The dose rates along the maze decreased exponentially towards the maze entrance and were significant for short maze lengths. The evaluated empirical methods for estimating neutron dose rates at the maze entrance of a linac proposed by Kersey, the modified Kersey method and Falcão method, agree by a factor of two from the experimental measurements. The results revealed vital radiation protection considerations owing to neutron contamination in external beam therapy.

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Serpentinites are metamorphic rocks that are widely applied as aggregates in the production of radiation-shielding concrete. Different varieties of massive serpentinite mountains located in Egypt exist without real investment. Hence, this study aims to evaluate the radiation shielding efficacy of three varieties of serpentinite rocks from different geological perspectives: mineralogical, geochemical, and morphological characteristics. X-ray diffraction, transmitted-light microscopy, and thermal analysis were required to characterize their mineralogical composition, while X-ray fluorescence was necessary to investigate their geochemical features. Moreover, scanning electron microscopy was used to detect their morphological characteristics. On the other hand, the PuBe source and stilbene detector were employed for the experimental determination of fast neutrons and γ-ray attenuations, which were conducted at energy ranges of 0.8−11 and 0.4−8.3 MeV, respectively. Based on the mineralogical, geochemical, and morphological characteristics of these rocks, the radiation attenuation capacity of lizardite > antigorite > chrysotile. However, these serpentinites can be applied as a natural alternative to some radiation-shielding concrete in radiotherapy centers and other counterpart facilities.

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We propose determining the entrance surface air kerma (ESAK) from the kerma area product (PKA) in digital radiology. ESAK values were derived from the X-ray tube outputs and patient exposure factors across five X-ray departments. Using linear regression between ESAK and PKA values, the slope and intercept coefficients were determined for each X-ray equipment and procedure. The method was examined using the data collected from patients who underwent chest PA/LAT, abdomen, pelvic AP, and lumbar spine AP/LAT X-ray examinations. The results showed a highly significant correlation between ESAK and PKA values and correlation coefficients, ranging from 0.77 to 1 with P-value < 0.001 in most studies. This method can be employed by incorporating dose data and related parameters into the X-ray device's software, similar to other dose-displayed information. The online determination of ESAK from PKA could help with quality assurance and patient dose management in digital radiology.

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Natural and 137Cs radioactivity in coastal marine sediment samples was measured using gamma spectrometry. Samples were collected at 16 locations from four beaches along the coastal area of Muscat City, Gulf of Oman. Radioactivity in beach sand was used to estimate the radiological risk parameters to humans, whereas the radioactivity in marine sediments was used to assess the radiological risk parameters to non-human biota, using the ERICA Tool. The average radioactivity concentrations (Bqkg-1) of 226Ra, 232Th, 40K, 210Pb and 137Cs in sediments (sand) were as follows: 16.2 (16.3), 34.5(27.8), 54.7 (45.6), 46.8 (44.9) and 0.08 (0.10), respectively. In sand samples, the estimated average indoor (Din) and outdoor (Dout) air absorbed dose rates due to natural radioactivity were 49.26 and 27.4 and the total effective dose (AEDTotal; µSvy-1) ranged from 150.2 to 498.9 (average: 275.2). The measured radioactivity resulted in an excess lifetime cancer risk (ELCR) in the range of 58-203 (average: 111) in and an average gonadal dose (AGD; µGy.y-1) ranged from 97.3 to 329.5 (average: 181.1). Total dose rate per marine organism ranged from 0.035 µGy h-1 (in zooplankton) to 0.564 µGy h-1 (in phytoplankton). The results showed marine sediments as an important source of radiation exposure to biota in the aquatic environment. Regular monitoring of radioactivity levels is vital for radiation risk confinement. The results provide an important radiological risk profile parameter to which future radioactivity levels in marine environments can be compared.

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This paper presents guidelines for the calibration of radiation beams that were issued by the International Atomic Energy Agency (IAEA TRS 398), the American Association of Physicists in Medicine (AAPM TG 51) and the German task group (DIN 6800-2). These protocols are based on the use of an ionization chamber calibrated in terms of absorbed dose to water in a standard laboratory's reference quality beam, where the previous protocols were based on air kerma standards. This study aims to determine uncertainties in dosimetry for electron beam radiotherapy using internationally established high-energy radiotherapy beam calibration standards. Methods: Dw was determined in 6-, 12- and 18 MeV electron energies under reference conditions using three cylindrical and two plane-parallel ion chambers in concert with the IAEA TRS 398, AAPM TG 51 and DIN 6800-2 absorbed dose protocols. From mean measured Dw values, the ratio TRS 398/TG 51 was found to vary between 0.988 and 1.004, while for the counterpart TRS 398/DIN 6800-2 and TG 51/DIN 6800-2, the variation ranges were 0.991-1.003 and 0.997-1.005, respectively. For the cylindrical chambers, the relative combined uncertainty (k = 1) in absorbed dose measurements was 1.44%, while for the plane-parallel chambers, it ranged from 1.53 to 1.88%. Conclusions: A high degree of consistency was demonstrated among the three protocols. It is suggested that in the use of the presently determined dose conversion factors across the three protocols, dose intercomparisons can be facilitated between radiotherapy centres.

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In this study, we sought to estimate the patient radiation doses in the digital radiography X-ray examinations conducted in a large hospital. The patient exposure factors and kerma-area product (PKA) were retrospectively recorded via the Digital Imaging and Communications in Medicine (DICOM) header for 547 patients. The entrance surface air kerma (ESAK) was estimated from the measurements of the X-ray tube output and recorded exposure factors, as well as from the console that displayed PKA as an alternative method. Effective doses were estimated from ESAK and PKA values using the appropriate conversion coefficient. In the chest PA, chest LAT, cervical spine AP, cervical spine LAT, abdomen AP, pelvis AP, lumbar spine AP, and lumbar spine LAT, the median ESAK (mGy) was found to be 0.13, 0.27, 0.35, 0.52, 0.70, 1.06, 2.33, and 4.18 mGy, respectively. Median PKA values were 0.10, 0.26, 0.14, 0.17, 0.77, 0.68, 0.81, and 1.11 Gy cm2, respectively. The estimated effective dose from ESAK and PKA values yielded comparable results. The comparison revealed that the ESAK and PKA values fell far below the reported in the literature. The results showed that the information of the DICOM deader is valuable for dosimetry and optimization.

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This study was performed to measure the entrance surface air kerma (ESAK) for optimisation of chest X-ray examination of children in general radiography hospitals in Khartoum. ESAK was estimated using the X-ray tube output exposure and patient-specific exposure parameters collected during routine examinations. The estimated ESAK values per radiography ranged from 17 to 89 µGy, 32 to 161, 67 to 242, 77 to 278; and from 95 to 389 µGy for Newborn, 1, 5, 10 and 15 y children, respectively. Doses are comparable with a previous study and are somewhat higher than the UK reference dose levels. The study demonstrated the necessity to follow guidelines for quality radiograph as a key element in the optimisation of X-ray examination of children. Frequent dose measurements are of particular importance for the optimisation of X-ray examination of children in general radiography hospitals.

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