Radiation protection dosimetry最新文献

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.

Soil samples were collected from vegetable agricultural areas in and around Addis Ababa, and their levels of radioactivity were measured. Gamma spectrometry with high-purity germanium detector was used to quantify radioactivity level. The average concentration of 226Ra, 232Th, and 40K were 32.8 ± 2.1, 62.4 ± 4.4, and 544.3 ± 23.3 Bq kg-1 respectively. The mean values of 232Th and 40K are higher, whereas the value of 226Ra is comparable with world average values. Radiological hazard indices, including radium equivalent activity (Raeq), absorbed dose rate (Dr), outdoor annual effective dose equivalent (Deff), external hazard index (Hex), internal hazard index (Hin), and gamma radiation representative level index (Iγ), were calculated based on the activity concentration of 226Ra, 232Th and 40K. The mean values were 163.9 Bq kg-1, 78.7 nGy h-1, 0.10 mSv y-1, 0.44, 0.53, and 0.60 respectively. All indices are lower than global recommended limit values. These results revealed that radiation hazard due to radionuclides in the soil of the study area is insignificant.

Despite the growing use of dose management systems (DMSs), there is limited guidance on their optimal setup. This study aims to fill this gap by outlining the process followed to integrate "DOSE" (Qaelum NV, Belgium) DMS within the Cypriot public hospitals. DOSE was connected to the available central PACS, followed by a thorough data and functioning validation. A preliminary study was also conducted to assess the DOSE's ability to establish typical dose values in diagnostic radiography. Overall, over 70 x-ray units were configured. For some connections, it was necessary to first adjust the unit's DICOM attributes or to utilise the DICOM coercion technique. The DICOM image header was sometimes preferred over the DICOM RDSR, as the chosen data source. This study underscored the importance of understanding the equipment's technical capabilities for a successful DMS integration, while personnel with expertise in diagnostic radiology and the IT aspects of medical physics proved to have a vital role in the process. The pilot study showed that DOSE is an effective tool for establishing typical dose values and assessing compliance with relevant dose levels.

This paper presents a new method for correcting the contribution of scattered radiation to the measurement of 99mTc internal activity in nuclear medicine patients using gamma cameras. So, this study aims to derive scattering correction factors by Monte Carlo simulation for anterior and posterior count rates (${I}_{mathrm{A}}$ and ${I}_{mathrm{P}}$) in the conjugate view method, enabling more precise estimation of activity A(t) compared to traditional trapezoidal and triangular approximations. The new approach eliminates the need to use photopeak for determining the fraction of scattered photons. Our results showed differences of <3% with respect to the real activity and 11% for the trapezoidal and triangular approaches.

In recent years, scientific communities have been concerned about the potential health effects of periodic electromagnetic field exposure (≤1 h/d). The objective of our study is to determine the impact of extremely low-frequency pulsed electromagnetic fields (ELF-PEMF) (1-3 mT, 50 Hz) on mouse fibroblast (red fluorescent protein (RFP)-L929) cells and adult Wistar rats to gain a comprehensive understanding of biological effects. We observed that RFP-L929 exhibits no significant changes in cell proliferation and morphology but mild elevation in aspartate aminotransferases, alanine aminotransferases, total bilirubin, serum creatinine, and creatine kinase-myocardial band levels in ELF-PEMF exposed groups under in vitro and in vivo conditions. However, the histological examination showed no significant alterations in tissue structure and morphologies. Our result suggests that 50-Hz ELF-PEMF exposure (1-3 mT, 50 Hz) with duration (<1 h/d) can trigger mild changes in biochemical parameters, but it is insufficient to induce any pathological alterations.

Surface contamination monitors are used intensively in many facilities, like in the nuclear medicine departments for clearance measurements and decontamination and in decommissioning of nuclear installations. For a reliable use, all surface contamination monitors should have a valid calibration with traceability to the international standards. A comparison exercise for calibrations in terms of efficiency in 2π steradian for surface contamination monitors was organized between five dosimetry calibration laboratories, members of EURAMET (The European Association of National Metrology Institutes). Four β-beta radionuclide sources, Sr-90, Cl-36, Cs-137, Co-60, and one α-alpha source, Am-241, were used for calibrations during this exercise. Two transfer surface contamination monitors, one Canberra SABG 100 and one Berthold LB 124 with 100 cm2 and 343 cm2 effective area, respectively, were used. The monitors were circulated between the partners and were periodically returned to the pilot laboratory for stability checks. The efficiencies in 2π steradian measured by the participants do not fully agree for all sources and both detectors despite the fact that all laboratories used similar types of surface contamination sources and had proper traceability to primary standards for surface emission rate measurements. As no evident difference in measurements of surface emission rates is expected between the primary standard laboratories that calibrated the sources, it is very probable that the observed differences are mainly due to the calibration procedures used by each laboratory and that the measurement uncertainties of efficiency in 2π steradian are underestimated. This report presents the results of this pilot comparison for calibration of surface contamination monitors and stresses the need to organize similar generalized exercises. This report also identifies some gaps in procedures for calibration of surface contamination monitors.

The aim of the study is to establish local diagnostic reference levels (DRLs) in cerebral thrombectomy, according to the anatomical region of ischemic stroke. This is a retrospective study from a single center involving 255 examinations. The proposed median values (P50) for thrombectomy are: 123 Gy.cm2 for air kerma-area product (PKA) and 915 mGy for air kerma (Ka,r). For middle cerebral artery (MCA) thrombectomies, the proposed DRLs are 118 Gy.cm2 for PKA and 112 Gy.cm2 for internal carotid artery (ICA). The Ka,r values for MCA and ICA are 849 and 775 mGy, respectively. It was observed that 94.9% of patients presented grade 0 on the initial modified treatment in cerebral infarction (mTICI) scale, and after thrombectomy, 63.1% of patients reached a final mTICI grade of 3. Stents were implanted in 37 patients (14.5% of cases). It was concluded that 16.1% of patients exceeded one trigger value of the Safety in Radiological Procedures' recommended parameters. Establishing DRLs is an important tool for optimizing practices and is considered a standard for quality control.

This paper focuses on the neutron spectrum measurement using a liquid scintillation detector, where the neutron spectrum could be identified and unfolded from the light output distribution of the EJ-301 liquid scintillation detector through a linear artificial neural network (ANN). The response functions of the EJ-301 detector for monoenergetic neutron sources, as well as the light outputs, have been simulated and calculated by Monte Carlo procedure FLUKA. The linear ANN was trained and tested through the simulated data, where response functions were set as the input of ANN and the corresponding neutron spectra were output. Therefore, the neutron spectrum-unfolding model was created. This spectrum-unfolding model was tested through the light outputs induced by monoenergetic neutrons and the random superposition of them. Unfolding results show that this model could identify the information of the neutron spectrum accurately from the light outputs of a liquid scintillation detector. Moreover, the EJ-301 detector was used to measure the radioactivity of 252Cf, and the pulse height distribution induced by neutrons was derived through the charge-comparison method to remove the influence of gamma rays. The measured pulse height distribution was unfolded by the trained model, and measured results show that the unfolded neutron spectrum of 252Cf was consistent with the reference one. This paper presents the feasibility that the unknown neutron spectrum could be identified and confirmed through a linear neural network trained by simulated monoenergetic neutron response functions, which could be a candidate of choice for the determination of the neutron spectrum.