Radiation protection dosimetry最新文献

Background and aims: Healthcare professionals involved in fluoroscopy-guided endoscopy are occupationally exposed to ionizing radiation. We evaluated whether a patient-immobilization device, MEDO V-Fix®, reduces this exposure.

Methods: Monthly effective and lens equivalent dose were measured for nurses and doctors using personal dosemeters worn inside protective gear. Data from 7 months before and 10 months after device introduction were compared. Additionally a cost-benefit analysis (CBA) of dose reduction was performed.

Results: Monthly effective doses fell in both professions, but neither decline reached statistical significance. By contrast, nurses' mean lens-equivalent dose dropped sharply from 35.0 to 6.5 μSv per procedure (P < 0.01), whereas the reduction in doctors was not significant. In the CBA, assuming a 5-y service life, the benefit-to-cost ratio ranged 1.02-2.72, indicating economic merit.

Conclusions: The MEDO V-Fix significantly reduces the occupational radiation exposure of endoscopy nurses and is a worthwhile investment from a CBA perspective.

Numerical dosimetry for assessments of the absorbed power density (APD) and temperature rise has been conducted using multi-layer skin models, incorporating skin, fat, muscle, and other components, providing a scientific foundation for setting exposure limits. However, the influence of the vasculature on dosimetry outcomes remains underexplored. In this study, we developed a synthetic blood vessel model and integrated it into multi-layer skin models. Electromagnetic computations were performed, followed by steady-state temperature rise evaluations using the Pennes bioheat transfer equation across a frequency range of 3 to 30 GHz. To quantify the effect of vascular modeling on dosimetry results, simulations incorporating vasculature with varying endpoint diameters were compared to those without vasculature. Results showed that the effect of vascular modeling on peak spatial-averaged APD was negligible, and its influence on peak temperature rise was ~8% at 3 GHz, decreasing to less than <3% above 6 GHz. And the effect of the endpoint diameter is marginal. These variations are smaller than those previously reported due to changes in tissue thickness and dielectric or thermal properties. While the effect on peak temperature rise is modest, including vasculature helps refine localized thermal distributions and may inform future improvements in anatomical modeling.

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.