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MS2 coliphage and <i>E. coli</i> UVB inactivation rates in optically clear water: dose, dose rate and temperature dependence
摘要： Natural ultraviolet irradiance disinfection is known to play a significant role in both natural wastewater treatment systems and drinking water disinfection processes, while the influence of ultraviolet B (UVB) delivering method on sunlight disinfection outcome is still unclear. This study aims to determine the effects of environmentally relevant temperatures, UVB doses (J m?2) and dose rates (W m?2) on the inactivation and log reduction values (LRVs) of the F-RNA coliphage MS2 and Escherichia coli in optically clear water. E. coli and MS2 were separately incubated and irradiated at five different doses of UVB light that delivered using six UVB dose rates. The results of the study demonstrate that the UVB dose delivering method (combination of dose rate and exposure time) influences inactivation and LRVs of E. coli and MS2 at all UVB doses investigated (up to seven-fold difference). Two phases were identified within the UVB dose rate, UVB inactivation or LRV curves for both organisms; a UVB dose rate limited inactivation phase and a dose rate saturation inactivation phase. The results contribute to a better understanding of UVB disinfection in the environment and natural wastewater treatment systems, potentially improving the design and operation of high rate algal ponds.
关键词： temperature,dose,dose rate,E. coli,MS2,UVB,inactivation
更新于2025-09-19 17:15:36
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Quantitative analysis of radiation dosage and image quality between digital breast tomosynthesis (DBT) with two-dimensional synthetic mammography and full-field digital mammography (FFDM)
摘要： Purpose: Currently in diagnostic setting for breast cancer, FFDM and DBT are performed conjunctively. However, performing two imaging modalities may increase radiation exposure by double. Two-dimensional reconstructed images created from DBT with 2DSM, has a potential to replace conventional FFDM in concerning both radiation dosage and image quality. With increasing concerns for individual radiation exposure, studies analyzing radiation dosage in breast imaging modalities are needed. This study compared radiation dosage and image quality between DBT + 2DSM versus FFDM. Methods and materials: 374 patients (mean age 52 years) who underwent both DBT and FFDM were retrospectively reviewed. Radiation dosage data were obtained by radiation dosage scoring and monitoring program Radimetrics (Bayer HealthCare, Whippany, NJ). Entrance dose and mean glandular doses in each breast were obtained for both modalities. To compare image quality of DBT + 2DSM and FFDM, a 5-point scoring system for lesion clarity was assessed. The parameters of radiation dosage (entrance dose, mean glandular dose) and image quality (lesion clarity scoring) were compared. Results: For entrance dose, DBT had lower mean dosage (14.8 mGy) compared with FFDM (21.8 mGy, p-value < 0.0001). Mean glandular doses for both breasts were lower in DBT (Left 1.74, Right 2.1) compared with FFDM (Left 2.85, Right 2.74, p-value < 0.0001). Lesion clarity score was higher in DBT with 2DSM (mean score 4.03) compared with FFDM (3.82, p-value < 0.0001). Conclusion: DBT showed lower radiation entrance dose and mean glandular doses to both breasts compared with FFDM. DBT + 2DSM had better image quality than FFDM, suggesting that DBT with 2DSM has potential as an alternative to FFDM.
关键词： Radimetrics,Full-field digital mammography,Image quality,2-Dimensional synthetic mammography,Digital breast tomosynthesis,Radiation dose
更新于2025-09-19 17:15:36
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Investigation of shutter scan acquisition parameters in a prototype chest digital tomosynthesis system
摘要： A shutter scan acquisition (SSA) method is proposed to reduce patient exposure dose in a chest digital tomosynthesis system. Projections obtained using the SSA constitute a combination of truncated and non-truncated projections. The truncated projections are images in which the lung field is set within a region-of-interest (ROI), and the non-truncated projections are full images in which the ROI is not set at all. We proposed a shutter weighting factor (SWF) as an acquisition parameter for SSA. We call the number of truncated projections divided by the number of non-truncated projections as SWF. We used a prototype CDT system and the LUNGMAN phantom with 8 and 10 mm lung nodules. 81 projections were obtained using SSA in five sets according to the SWFs. The image quality was quantified based on the contrast-to-noise ratio (CNR). We also calculated the figure of merit (FOM) to determine the proper acquisition parameters of the five sets. Both the CNR and FOM values of the 8 mm lung nodule in the selected ROI increased with increases of the SWF. However, the CNR value of the 10 mm lung nodule outside the ROI decreased with increases of the SWF, while the FOM value was maximized when the SWF was 3.05. We investigated the effect of the composition ratio of the truncated and non-truncated projections on the reconstructed images of the SSA based on the FOM values. In conclusion, we determined the proper SSA parameters in a prototype CDT system.
关键词： Digital tomosynthesis,Dose reduction method,Region of interest reconstruction,Shutter scan acquisition
更新于2025-09-19 17:15:36
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Low-dose single-energy material decomposition in radiography using a sparse-view computed tomography scan
摘要： Dual-energy material decomposition (DEMD) is a well-established theoretical x-ray technique that uses low- and high-kilovoltage radiographs to separate soft tissue and bone in radiography and computed tomography (CT). However, it requires double exposures that result in increased patient radiation doses, causes increases in the execution time, and generates errors due to misregistration attributed to the patient motion between two scans. In this study, we investigated a low-dose, single-energy material decomposition (LSEMD) method in radiography using a sparse-view computed tomography scan where the attenuation length in the object was estimated from the CT image. We performed a systematic simulation and an experiment to demonstrate the feasibility of use of the LSEMD method in radiography. Only 60 projections, far fewer than those required by the Nyquist sampling theory, were acquired at an x-ray tube voltage of 80 kVp, and were used to reconstruct a sparse-view CT image with a state-of-the-art dictionary-learning (DL) algorithm. We investigated the image performance of the LSEMD and compared the elicited results with those obtained with the use of DEMD (80 kVp and 120 kVp were used). Our results indicate that the DL algorithm produced high-quality sparse-view CT images. Accordingly, the LSEMD method yielded material decomposition results that were very similar to the results elicited by the conventional DEMD method in radiography.
关键词： dictionary-learning,low-dose single-energy material decomposition,Computed tomography,dual-energy material decomposition
更新于2025-09-19 17:15:36
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Diagnostic Reference Levels for Diagnostic and Interventional X-Ray Procedures in Germany: Update and Handling
摘要： Purpose Recent developments in medical technology have broadened the spectrum of X-ray procedures and changed exposure practice in X-ray facilities. For this reason, diagnostic reference levels (DRLs) for diagnostic and interventional X-ray procedures were updated in 2016 and 2018, respectively. It is the aim of this paper to present the procedure for the update of the DRLs and to give advice on their practical application. Materials and Methods For the determination of DRLs, data from different independent sources that collect dose-relevant data from different facilities in Germany were considered. Seven different weight intervals were specified for classifying pediatric X-ray procedures. For each X-ray procedure considered, the 25th, 50th, and 75th percentile of the respective national distribution of the dose-relevant parameters were determined. Additionally, effective doses that correspond to the DRLs were estimated. Results In procedures with already existing DRLs before 2016, the values were lowered by circa 20 % on average. Numerous DRLs were established for the first time (9 for interventional procedures, 10 for CT examinations). Conclusion For dose optimizations even below the new national DRLs, the BfS recommends establishing local reference levels, using dose management software (particularly in CT and interventional radiology), adapting dose-relevant parameters of X-ray protocols to the individual patient size, and establishing internal radiation protection teams responsible for optimizing X-ray procedures in clinical practice. When applying good medical practice and using modern equipment, the median dose values of the nationwide dose distributions can not only be easily achieved but can even be undercut.
关键词： pediatric X-ray examinations,diagnostic and interventional radiology,patient exposure,dose optimization and reduction,diagnostic reference levels (DRLs)
更新于2025-09-19 17:15:36
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Gate Bias and Length Dependences of Total-Ionizing-Dose Effects in InGaAs FinFETs on Bulk Si
摘要： We evaluate the total-ionizing-dose (TID) responses of InGaAs nMOS FinFETs with different gate lengths irradiated with 10-keV X-rays under different gate biases. The largest degradation after irradiation occurs at VG = -1 V. Radiation-induced trapped positive charge dominates the TID response of InGaAs FinFET transistors, consistent with previous results for InGaAs multi-fin capacitors. Shorter gate-length devices show larger radiation-induced charge trapping than longer gate-length devices, most likely due to the electrostatic effects of trapped charge in the surrounding SiO2 isolation and SiO2/Si3N4 spacer oxides. 1/f noise measurements indicate a high trap density and a non-uniform defect-energy distribution, consistent with a strong variation of effective border-trap density with surface potential.
关键词： 1/f noise,FinFETs,InGaAs,Total-Ionizing-Dose,Bulk Si,border-trap,Gate length dependence,III-V
更新于2025-09-19 17:15:36
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Melatonin suppression is exquisitely sensitive to light and primarily driven by melanopsin in humans
摘要： Introduction: Light elicits a range of non-visual responses in humans. Driven predominantly by intrinsically photosensitive retinal ganglion cells (ipRGCs), but also by rods and/or cones, these responses include melatonin suppression. A sigmoidal relationship has been established between melatonin suppression and light intensity, however photoreceptoral involvement remains unclear. Methods and Results: In this study, we first modelled the relationships between alpha-opic illuminances and melatonin suppression using an extensive dataset by Brainard and colleagues. Our results show that 1) melatonin suppression is better predicted by melanopic illuminance compared to other alpha-opic illuminances, 2) melatonin suppression is predicted to occur at levels as low as ~1.5 melanopic lux (melanopsin-weighted irradiance 0.2 μW/cm2), 3) saturation occurs at 305 melanopic lux (melanopsin-weighted irradiance 36.6 μW/cm2). We then tested this melanopsin-weighted illuminance response model derived from Brainard and colleagues’ data and show that it predicts equally well melatonin suppression data from our laboratory, although obtained using different intensities and exposure duration. Discussion: Together, our findings suggest that melatonin suppression by monochromatic lights is predominantly driven by melanopsin, and that it can be initiated at extremely low melanopic lux levels in experimental conditions. This emphasizes the concern of the non-visual impacts of low light intensities in lighting design and light-emitting devices.
关键词： melatonin,light,mathematical model,dose-response relationship,humans,circadian,melanopsin
更新于2025-09-19 17:15:36
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Effect of Temperature and Electrical Modes on Radiation Sensitivity of MISFET Dose Sensors
摘要： The temperature and electrical modes influences on radiation sensitivity of n-channel MISFETs sensors of the total ionizing dose were investigated. There were measured the MISFET-based dosimeter output voltages V as function of the radiation doses D at const values of the drain current IDand the drain–source voltage VD, as well as the (ID–VG) characteristics before, during and after irradiations at different temperatures T (VGis the gate voltage). It was shown how the conversion function V(D) and the radiation sensitivity SD are depending on the temperature T for different electrical modes. To interpret experimental data there were proposed the models taking into account the separate contributions of charges in the dielectric Qt and in SiO2–Si interface Qs. The model’s parameters ΔVt(D,T) and ΔVs(D,T) were calculated using the experimental ID–VG characteristics. These models can be used to predict performances of MISFET-based devices.
关键词： electrical modes,ionizing dose sensors,radiation sensitivity,temperature,MISFET
更新于2025-09-19 17:15:36
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Statistic and dosimetric criteria to assess the shift of the prescribed dose for lung radiotherapy plans when integrating point kernel models in medical physics: are we ready?
摘要： Background: To apply the statistical bootstrap analysis and dosimetric criteria’s to assess the change of prescribed dose (PD) for lung cancer to maintain the same clinical results when using new generations of dose calculation algorithms. Methods: Nine lung cancer cases were studied. For each patient, three treatment plans were generated using exactly the same beams arrangements. In plan 1, the dose was calculated using pencil beam convolution (PBC) algorithm turning on heterogeneity correction with modified batho (PBC-MB). In plan 2, the dose was calculated using anisotropic analytical algorithm (AAA) and the same PD, as plan 1. In plan 3, the dose was calculated using AAA with monitor units (MUs) obtained from PBC-MB, as input. The dosimetric criteria’s include MUs, delivered dose at isocentre (Diso) and calculated dose to 95% of the target volume (D95). The bootstrap method was used to assess the significance of the dose differences and to accurately estimate the 95% confidence interval (95% CI). Wilcoxon and Spearman’s rank tests were used to calculate P values and the correlation coefficient (ρ). Results: Statistically significant for dose difference was found using point kernel model. A good correlation was observed between both algorithms types, with ρ>0.9. Using AAA instead of PBC-MB, an adjustment of the PD in the isocentre is suggested. Conclusions: For a given set of patients, we assessed the need to readjust the PD for lung cancer using dosimetric indices and bootstrap statistical method. Thus, if the goal is to keep on with the same clinical results, the PD for lung tumors has to be adjusted with AAA. According to our simulation we suggest to readjust the PD by 5% and an optimization for beam arrangements to better protect the organs at risks (OARs).
关键词： point kernel,bootstrap,Pencil kernel,anisotropic analytical algorithm (AAA),prescribed dose (PD)
更新于2025-09-19 17:15:36
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Empirical Law to Evaluate the Skin Dose with Photon Beam Energy and Irradiation Field Size
摘要： The objective of this study is to evaluate mathematically an empirical law governs the skin dose with photon beam energy and irradiation field size based on experiment data of dose distributions. The dose distributions were expressed on percentage depth dose (PDD). The measurements of PDDs were done as a function of irradiation field size with an uncertainty of 2% as recommended by IAEA protocols. The skin dose corresponds to PDD at depth of 0 mm for photon beam energy of 6 and 18 MV. For these both photon beam energies, the skin dose increased linearly with irradiation field size and the skin dose rate decreased in power law as a function of irradiation field size with mathematical error under to 10%. This law allows us to predict the skin dose with irradiation field size for high radiotherapy quality and high protection of organ at risks.
关键词： skin dose,linac,dosimetry,radiotherapy,PDD
更新于2025-09-19 17:15:36