Radiation protection dosimetry最新文献

Radon and thoron exhalation rates from samples are estimated by the standard closed-loop technique using online radon monitors. Conventionally, the mass balance equation is formulated by considering the closed air volume of the sample chamber and the detector chamber put together. This model serves the purpose of estimating the radon/thoron exhalation rates for the prescribed pump flow rate of 1 L min-1 using RAD7 online monitor. The flow rate requirement is crucial for thoron measurement due to its short half-life. In the present work, an alternate model is proposed which simulates the dynamics of radon/thoron concentration dictated by the air entry and exit rate and brings out the effect of pump flow rate. This model is more of academic interest, where sample chamber and detector chamber are considered as two separate entities since they are separated by tubing. The mass balance equation is reformulated considering the air entry and exit in and out the individual chambers. The radon buildup in the sample chamber and detector chamber were treated separately by two coupled differential equations. The equations were numerically solved. The model reiterated the fact that the lower flow rates do not affect the buildup profile of relatively long-lived 222Rn (half-life 3.8 d) and its steady-state concentration attained in the closed air volume. However, experiments carried out for flow rates 0.3 and 0.5 L min-1 with RAD7 monitor using powdered granite sample with higher 226Ra and 232Th concentrations gave contradicting results. The radon effective removal rate was found to decrease with increase in flow rate from 0.3 to 1 L min-1. This issue was investigated, and it was speculated that the thoron interference problem might not be properly addressed for flow rates <1 L min-1. This was ascertained by observing the effective radon removal rate in the absence of thoron by conducting radon decay experiments with different flow rates. For the case of short-lived thoron (half-life 55 s), the model described the dynamics of thoron concentration in the closed loop and the steady-state concentrations attained in the detector and sample chamber. As expected, the model showed that due to decay losses during transit of thoron between the chambers, the steady-state concentrations attained in the chambers considerably differ from each other even for 1 L min-1 flow rate.

In recent decades, technological advances have been made in the field of radiotherapy and with it the emergence of new dosimetric systems for their calibration and commissioning, among other uses. Such is the case of the measurement in the build-up region, where there is no charged-particle equilibrium, which is reflected in the increase in surface dose for patient treatments and potential skin toxicities as a secondary effect. This study utilizes optically stimulated dosemeters (nanoDot) and the radiochromic film (EBT3) to measure skin doses in patients with head and neck cancer who received radiotherapy. Accurately depicting 15 patients with different diagnoses from 3 linear accelerators using 3D, intensity modulated radiation therapy, or volumetric arc therapy/RapidArc technology, these results were compared with those calculated in the treatment planning system (TPS) and obtaining a percentage of variation for the EBT3 ranged from 0.30% to 6.15%, while that observed for the nanoDot was from 0.51% to 4.88%. This difference may be attributed to the reproducibility of placement in patients. Therefore, for clinical use, nanoDot dosemeters are a viable alternative for in vivo dosimetry where rapid validation of planning system results is required.

As the International Commission on Radiological Protection lowers the equivalent dose limit for lens of the eye of radiation workers, the importance of radiation protection for the lens of the eye has been increased. In the case of poor working condition, such as high temperatures and humid environments at nuclear power plants, wearing an eye dosemeter near the worker's eye may interfere with work. In addition, it would not be reasonable for all workers to wear an eye dosemeter to evaluate the lens equivalent dose even in areas with an expected low exposure dose in the NPPs. Therefore, it is necessary to develop an indirect assessment method for lens equivalent dose. The purpose of this study is to develop an indirect assessment method for a lens equivalent dose using correlation factors between whole-body dose and eye. The correlation factors are calculated by MCNP simulation results.

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.

The effect of patient shielding on fetal radiation dose was evaluated in computed tomography pulmonary angiography with the out-of-plane shield visible in the localizer but absent in the scan range in chest computed tomography (CT). An anthropomorphic phantom with additional prosthetic pregnancy belly was scanned with different CT scanners using clinical imaging protocols and radiophotoluminescence dosemeters (GD-352 M). The out-of-plane shield decreased the fetal absorbed radiation dose with Siemens Somatom go.Up, Canon Aquilion Prime SP and Canon Aquilion One scanners. The decrease was 3.9%-39.4% (0.01-0.09 mGy). With GE Optima the shield increased the fetal dose by 100% (0.23 mGy), with Canon Aquilion One and GE Optima scanners the abdomen dose increase was 17.5% and 36.4%, respectively (0.61 and 1.38 mGy). Applying an out-of-plane shield outside the scanned volume may increase the fetal radiation dose during CT when using tube current modulation, depending on the make and model of the CT scanner.

To become registered radiation worker as radiographer, nuclear medicine (NM) technologist, or radiotherapist in Australian health system, a 4-y bachelor's degree, or a 2-y master's degree in medical imaging (MI), NM, or radiation therapy (RT) approved by the Australian Health Practitioner Regulation Agency is required. During their supervised clinical practice period, it is crucial to monitor students' occupational radiation dose as their annual dose limit is 1 mSv y-1 unlike regular occupational dose of 20 mSv y-1. In this study, the distribution and trend of occupational dose among over 300 radiography, NM, and radiotherapy student practitioners per year in an Australian university are analyzed over a period of 10 y (2013-22). The overall average annual effective dose was well below the dose limit set for the students. Among the three streams-MI, NM, and RT-NM students had the highest annual dose.

The World Health Organization (WHO) recommends that countries adopt the reference level of 100 Bq m-3 for indoor radon gas. Adopting the reference level requires a preliminary assessment of the indoor radon concentration. In the preliminary investigation, a cut-off value is useful, which is a value for selecting samples that can be reliably determined to be below the reference level (in this paper, the WHO reference level) using a straightforward method. If the true value was the WHO reference level, then the cut-off value of the PicoRad collector for selecting samples was determined as 80 Bq m-3 through the analysis of the 95% prediction interval.

Senescence-like growth arrest (SLGA), which is a radiation-induced cell death pathway, is induced in immortalized normal human epithelial cell (hTERT-RPE1) by the daily fractionated X-irradiation with 1.5 Gy within 30 times. We here demonstrate that pre-treatment induces acquired radioresistance (ARR) that can survive from the lethal fractionated radiation. The parent cells were daily fractionated with 1.5 Gy for 5 d and then incubated for 7 d without fractionated radiation. After this, the daily fractionated radiation with 1.5 Gy was restarted. A small population of surviving cells appeared after 30 times of the daily fractionated radiation was completed and they were continuously growing up to 120 times of the daily fractionated radiation (RPE1-1.5Fr). We confirmed a higher basal expression level of p53, which functions in the activation of the SLGA pathway but fails to further accumulate after 1.5 Gy of single irradiation in RPE1-1.5Fr. It is the first report to induce ARR phenotype for fractionated radiation in normal human cells.

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident created large stockpiles of tritium containing cooling water, which is to be gradually released into the Pacific Ocean, gaining attention from surrounding countries, environmental groups, and local residents concerned with the possibility of increasing tritium concentrations in the water and food cycle. Establishing baseline concentration levels and monitoring tritium immission values are important for assuring public safety, providing data for scientific research and risk communication. Tritium concentrations in the environment are very low; therefore, tritium measurements require enrichment in order to estimate the radiation exposure from drinking water intake and provide information on the water cycle. Natural water samples were collected at Tomioka Town located south of the FDNPP. Samples were distilled, enriched by electrolysis, and re-distilled using an improved SPE method to preconcentrate tritium to measureable levels. Tritium concentrations were determined by a low-background liquid scintillation counter. The observed tritium concentrations were relatively low, rainwater had a mean and SD value of 0.40 ± 0.13 Bq/L, and freshwater samples showed similar concentrations, while brackish coastal water samples were below 0.13 ± 0.02 Bq/L. The observed tritium concentrations in this study are considered safe as effective doses based on annual drinking water intake; however, continous monitoring is necessary to assure public safety.