Radiation protection dosimetry最新文献

This study evaluated radiation dose to the eye lens and the shielding efficacy of a radiation-protective eye mask (E-Mask) during repeated chest and abdomen computed tomography (CT) scans. Dose measurements were obtained using an anthropomorphic phantom and an optically stimulated luminescence dosemeter (Model TOPAZ, LANDAUER, USA). A 5-y follow-up scenario for Hodgkin lymphoma was simulated by assuming one scan per quarter, with the single-scan dose multiplied by 20 to represent four scans annually over 5-y. Despite the use of low-dose protocols based on national diagnostic reference levels issued by the Korea Disease Control and Prevention Agency, unshielded cumulative lens doses reached 363.89 mSv (right) and 424.84 mSv (left). Using an E-Mask reduced these doses to 243.96 mSv and 240.13 mSv, corresponding to reductions of 32.96% and 43.48%, respectively. These findings support the use of the E-Mask in radiosensitive populations to reduce lens exposure during long-term CT follow-up.

In recent years, academia has sought the therapeutic applicability of periodic low-intensity electromagnetic field exposure (< 1 h/d) for biomedical applications. We have designed and developed a monoaxial Helmholtz coil chamber for non-invasive magnetic field exposure for therapeutic application, i.e. cancer therapy. In the current study, we observed 50 Hz extremely low-frequency pulsed electromagnetic field ELF-PEMF (1-3 mT) exposure effects on cell proliferation and morphology of cancer cell lines under in vitro conditions. We witnessed significant changes in cell proliferation and morphology of A549 cells for exposure durations of < 1 h/d. We also noticed a notable change in the actin cytoskeleton and shrinking of cell nuclei in A549 cells compared to the control groups. However, HepG2 and MCF-7 cells were notably unaffected by the current experimental conditions. The experimental evidence indicated that 50 Hz ELF-PEMF exposure of less than 1 h/d can significantly alter cell proliferation and induce morphological changes in A549 cells. This innovative, targeted, non-invasive method can be a popular therapeutic choice for patients with advanced stages of cancer. Moreover, exposure protocols will be much more helpful for clinicians depending on the patient's conditions, type of cancer cells, and exposure conditions, i.e. field intensities and duration.

Follow-up of the atomic bomb survivors in Japan in the Life Span Study (LSS) has been fundamental for the understanding of the dose-response curve. We compare our risk estimates from a newly published epidemiological study on cancer in Sweden after the Chernobyl Nuclear Power Plant accident with the LSS data. Hazard ratios (HRs) with 95% confidence intervals (95% CIs) were calculated using conditional logistic regression adjusted for rural/nonrural habitat, education level, and pre-Chernobyl cancer incidence from 1980 to 1985, respectively. Adjusted HRs by sex were calculated in deciles for all cancer sites combined for 1986 to 2020. These risk estimates were translated to excess relative risk (ERR) to allow comparison with LSS incidence data. ERRs per decile were compatible with ERR in the low-dose range <100 mGy for both sexes. The CIs in each decile need to be taken into account when interpreting the dose-response curve. Risk estimates in dose categories add important information at very low doses on the dose-response curve when compared to LSS data.

Physical grids (PGs) are used in portable bedside radiography to reduce scattered X-rays that reach the detector. Because the use of PGs degrades image quality due to oblique incidence of X-rays or deviation of the center line on the grid, scatter correction (SC) processing is often used instead of PGs. This study aimed to evaluate the relationship between object thickness and noise reduction in SC processing. Polymethyl methacrylate (PMMA) phantoms of different thicknesses (16, 20, 26, and 30 cm) were used as objects. The Burger phantom was placed at the center of the thickness direction of the PMMA phantoms. Images were acquired with PGs, without PGs, and with SC processing which consists of contrast improvement processing and noise reduction processing. Contrast and noise were evaluated. Contrast of images without PG improved when SC processing was used. However, the effect of noise reduction process decreased with increase in the thickness of PMMA, and significant decrease was observed when the thickness of PMMA was ≥26 cm. In SC processing, the effect of noise reduction decreased with the increase in object thickness. These findings suggest that the applicability of SC processing may be limited, particularly in large patients.

The high-purity germanium (HPGe) detector is used to quantify natural radioactivity concentrations in soil samples. The total uncertainty due to the contribution of the analytical method and sampling uncertainty is evaluated in this study. The relative sampling uncertainty values for 40K, 238U, and 232Th are found to be within 5%. The measured specific activity levels ranged between 225.6 ± 8.5 Bq/kg and 479.6 ± 13.0 Bq/kg for 40K, 12.1.6 ± 1.4 Bq/kg and 73.2 ± 2.7 Bq/kg for 238U, and 48.7 ± 2.6 Bq/kg and 548.7 ± 17.0 Bq/kg for 232Th, respectively. The radiological hazard parameters, such as absorbed dose rates and annual effective dose values, were estimated from the 40K, 238U, and 232Th activity concentration values. The absorbed dose rate values ranged between 45 nGy/h and 383 nGy/h with a mean value of 142 nGy/h. The annual effective dose values ranged from 0.06 mSv/y to 0.47 mSv/y with a mean value of 0.17 mSv/y.

The two-component model, comprising a fast-decay and a slow-decay component, has been widely used to approximate the decreasing trends of air dose rates in contaminated areas surrounding major nuclear accident sites. However, its adequacy is yet to be thoroughly validated. This study analyzed extensive car-borne survey data collected from 2011 to 2016 after the Fukushima Daiichi Nuclear Power Plant accident using the least absolute shrinkage and selection operator regression with a high-degree-of-freedom model. This analysis aimed to evaluate the adequacy of the two-component model and investigate the profiles of ecological half-lives. The results demonstrate that the two-component model can approximate the decreasing trend of air dose rates in the Fukushima area well in most cases. However, in ~20% of the cases, the one-component model provided a better fit. The fast-decay component in the two-component model exhibited a sharp ecological half-life peak below 1 y, with a frequency distribution peaking at 0.3-0.4 y. In contrast, the slow-decay component displayed a broader half-life peak in approximately half of the cases, with a frequency distribution spanning several years to over 50 y. The reduction speed of air dose rates was fastest in urban areas, followed by paddy fields, croplands, deciduous forests, and evergreen forests. The reduction speed decreased as the initial air dose rate increased, a trend explained by the weight assigned to the fast-decay component rather than the value of its ecological half-life. Future predictions of air dose rate distributions were made using a prediction model formula that incorporated the average ecological half-life profiles calculated for each land-use and initial air dose rate category. Prediction accuracy was verified through comparison with integrated map data, which merge air dose rate datasets obtained using different monitoring methods and represent the most currently reliable source. The predicted values tended to decay faster overall than the integrated map data, with an average deviation within 10% over the six-year period. This discrepancy arises because the car-borne survey data were collected on paved roads, where air dose rates decrease rapidly due to the quick washout of radiocesium. The differences between the prediction model values and integrated map values were larger for forests than for farmlands (paddy fields and croplands) and urban areas. This suggests that the reduction in air dose rates is slower in pure forests, where the car-borne surveys were rarely conducted.

The indoor radon concentration in a total of 143 rooms from 82 urban and 61 rural households in Ningxia was measured using the solid nuclear track method over four quarters for 1 y, followed by calculation of the annual effective dose. The results indicated that the mean of indoor radon concentrations was 88 Bq m-3, with a range from 39 to 226 Bq m-3. The concentrations exceeded 100 Bq/m-3 in 30% of the measurement locations, with two points measuring above 200 Bq/m-3, accounting for 1.4%. The indoor radon concentration was higher in rural areas compared to urban areas. Moreover, it exhibited a seasonal variation, with the highest levels observed during winter and the lowest during summer. Additionally, the effective dose of indoor radon among residents in Ningxia was calculated at 2.20 mSv a-1.

Internal audit at our radiology department identified variability in doses for computed tomography scans of the kidney, ureters, and bladder (CT KUB). This prompted a revision of the standard operating procedure (SOP) using less ambiguous osseous anatomical landmarks, namely the T10 vertebra endplate and inferior margin of the pubic symphysis. The objective of this study was to evaluate the use and effectiveness of SOPs as a means of scan length optimization and dose reduction. In total 247 CT-KUB scans were retrospectively analyzed in terms of compliance with the new osseous anatomical landmarks, and in terms of total scan length and dose-length product (DLP). The intervention comprised of two phases: (1) implementation of a new SOP with less ambiguous osseous anatomical landmarks, (2) amendment of the SOP, to assist identification of T10 endplate, by means of a sagittal scout view.This phased approach to SOP adjustments produced significant reduction in over-scanning. Excess over-scanning was reduced in the first phase, with a reduction of 14% in scan length and 32% in DLP. In the second phase, scan length was further reduced by 7%. Overall, scan length decreased by 20% and DLP by 55%.

In order to evaluate the field characteristics and instrument calibration capability of the 241Am-Be neutron reference radiation field at China Academy of Engineering Physics (CAEP), this paper conducted a series of researches on the radiation field. Firstly, the neutron energy spectrum of the field was investigated by multi-sphere spectrometer and Geant4. Secondly, the quantity transmission from China Institute of Atomic Energy (CIAE) to CAEP was achieved through the precision long counter system. In addition, three neutron dose rate meters from different manufacturers were calibrated in both the fields at CAEP and CIAE. Finally, the uncertainty of calibration factor for each instrument was calculated and validated in the two fields. The results demonstrated that the room scatter in the neutron radiation reference field at CAEP meet the requirement of ISO 8529 and the neutron energy spectrum measured in the field was acceptable. The range of neutron ambient dose equivalent rate that can be produced at CAEP and its uncertainty were determined. The calibration factors and their extended uncertainties obtained using two instruments in both fields were found to be reasonable and reliable. The radiation field established at CAEP can meet the routine calibration and experiment of common neutron dose rate meters.