Hasil untuk "Radioactivity and radioactive substances"

Yangfan Zhao, Deyi Chen, Yuxuan Wang et al.

Brígida Gomes de Almeida Schirmer, Juliana de Oliveira Silva, Douglas Boniek Silva Navarro et al.

Positron emission tomography (PET) is an important tool in preclinical studies in small animals, providing real-time insights into biochemical, metabolic, physiological, and functional processes. PET imaging also enables the assessment of biological responses and biodistribution of novel radiolabeled compounds within a single animal, minimizing the need for larger animal groups. In particular, PET imaging with [18F]DPA-714, a Translocator Protein (TSPO) ligand, has shown high predictive and prognostic value in diseases associated with neuroinflammation and correlates well with functional outcomes. In this study, basal expression of TSPO was investigated in vivo in C57BL/6 mice and PET was proposed as a method to track biodistribution of new molecules. Male C57BL/6 mice aged 6–9 weeks and weighing 20–30 g were divided into healthy and ischemic groups. The ischemic group was subjected to transient global cerebral ischemia induced by 25 min of bilateral common carotid artery occlusion (BCCAO) followed by reperfusion. Baseline imaging of [18F]DPA-714 biodistribution was performed in healthy mice with static whole-body scans at 0-20, 20-40, 40-60, and 60-80 min post-injection intervals. After ischemia, PET scans were used to examine the cerebral uptake of [18F]DPA-714. The results confirm that PET is an effective, non-invasive technique for biodistribution studies. Analysis of SUVmean, SUVmax, and SUVpeak metrics showed increased sensitivity for increased uptake in the brain following ischemia, highlighting its importance in preclinical neuroinflammation models. Furthermore, baseline uptake of [18F]DPA-714 was observed in multiple organs, reflecting the baseline expression of TSPO and its metabolic and clearance pathways. The comparable baseline uptake observed in the brain and muscle underscores its potential as a reliable marker for studying TSPO-related inflammatory processes.

L. A. Chipiga, K. N. Kozlova, I. A. Zvonova et al.

The development of nuclear medicine has led to an increase in the use of open radionuclide sources and the associated processes of transporting ionising radiation sources and generating radioactive waste. This situation leads to focus on monitoring and accounting of ionising radiation sources in hospitals. The aim of the study was assessment of geographical distribution and structure of nuclear medicine centres in theRussian Federation. Material and Methods: The register of sanitary and epidemiological conclusions on the compliance (non-compliance) of activities (works, services) with the requirements of state sanitary and epidemiological rules and regulations were analyzed at the beginning of 2025. Results: 188 hospitals operated with radionuclide, are located in the Russian Federation in 2025, including 152 single photon diagnostic nuclear medicine departments (38 in Moscow and 20 in St. Petersburg); 81 positron emission tomography departments (26 in Moscow and 8 in St. Petersburg); 52 radiopharmaceutical therapy departments (12 departments in Moscow and 5 in St. Petersburg). According to the results of the study, all radiopharmaceutical therapy departments are based in diagnostic nuclear medicine centers. Conclusion: The current practice of organizing radiopharmaceutical therapy units based on diagnostic nuclear medicine units does not allow to consider the radiation safety issues separately for diagnostics and therapy. It is reasonable to have uniform requirements for nuclear medicine units

Laila Fernanda Moreira de Almeida, Camila Engler, Peterson Lima Squair et al.

Mammography is crucial for the early detection of breast cancer, requiring periodic quality controls to ensure that images and patient exposure doses comply with regulatory limits. This study addresses the challenges involved in conducting quality control, such as the lack of qualified personnel and the subjectivity of daily evaluations with phantoms. Additionally, the research proposes the incorporation of automated and remote quality control tools. In this context, a simple phantom was developed by the IAEA using materials such as copper, acrylic, and aluminum, to be used with the Automated Tool for Image Analysis (ATIA) software. This software performs automatic image analyses, extracting data from the DICOM header and exporting it to a CSV file for analysis in Excel® spreadsheets. The objectives of this work were: (a) to manufacture the phantom according to the standard model from the IAEA Human Health Series No. 39 publication; (b) to apply the ATIA software in the daily monitoring of a mammography unit and the digital radiography (DR) image receptor retrofitted to an analog mammography unit at the Laboratory of Radioprotection Applied to Mammography (LARAM) of CDTN; (c) to evaluate and compare the responses obtained between the automated ATIA software and the manual IMAGEJ software. The results demonstrated the stability and consistency of the mammography system in metrics such as SDNR and SNR, essential for ensuring image quality. However, variabilities in horizontal and vertical MTF at lower spatial frequencies indicate discrepancies in resolving fine details. The detectability index (D') stood out for its high consistency, indicating the reliability of the mammography system in detecting small details. Thus, it can be inferred that significant differences between quality control software in various metrics highlight the importance of careful software selection to meet specific mammographic evaluation needs.

Daniel S. Lee, Mayra S. Haedo-Cruz, Chen Jiang et al.

Transformer-based deep learning models have shown promise for disease risk prediction using electronic health records(EHRs), but modeling temporal dependencies remains a key challenge due to irregular visit intervals and lack of uniform structure. We propose a Bi-Positional Embedding Transformer Encoder or BiPETE for single-disease prediction, which integrates rotary positional embeddings to encode relative visit timing and sinusoidal embeddings to preserve visit order. Without relying on large-scale pretraining, BiPETE is trained on EHR data from two mental health cohorts-depressive disorder and post-traumatic stress disorder (PTSD)-to predict the risk of alcohol and substance use disorders (ASUD). BiPETE outperforms baseline models, improving the area under the precision-recall curve (AUPRC) by 34% and 50% in the depression and PTSD cohorts, respectively. An ablation study further confirms the effectiveness of the dual positional encoding strategy. We apply the Integrated Gradients method to interpret model predictions, identifying key clinical features associated with ASUD risk and protection, such as abnormal inflammatory, hematologic, and metabolic markers, as well as specific medications and comorbidities. Overall, these key clinical features identified by the attribution methods contribute to a deeper understanding of the risk assessment process and offer valuable clues for mitigating potential risks. In summary, our study presents a practical and interpretable framework for disease risk prediction using EHR data, which can achieve strong performance.

L. Yu. Krestinina

The results of studies of long-term effects of population exposure in the South Urals in the 1950s were based for a long time on studies of the effects of exposure in the Techa River cohort and later in the East Urals Radioactive Trace cohort. After the creation of the South Urals Population Exposed to Radiation cohort, combining all persons exposed in the South Urals in the period from January 1, 1950, to December 31, 1960 the size of the cohort doubled, follow-up period reached 71 years, and the number of person-years at risk increased to 1,964,333. The average dose to red bone marrow for all cohort members was 231mGy. Regression analysis using a simple parametric excess relative risk model was performed using the EPICURE statistical package. The analysis resulted in confirmation of a statistically significant (p <0.001) linear doseresponse relationship of mortality for all hemoblastoses, and leukemia. The excess relative risk and 95% confidence intervals of death at 2-year latency period from all hemoblastoses were 0.71/Gy (0.28;1.31); from all leukemias - 1.28/Gy (0.55-2.39) and from leukemias excluding chronic lymphocytic leukemia -1.52/Gy (0.64-2.94). The quadratic model also significantly described the dose dependence; (the differences between the models were not significant). Increasing the follow-up period to 71 years resulted in a slight decrease in risk estimates. The width of the confidence intervals of the risk estimates decreased by more than a factor of 3 compared to earlier studies in the Techa River cohort, which indicates a decrease in uncertainties of risk estimates. Increasing the size of the cohort made it possible to obtain significant risk values for individual population groups (by sex, age, etc.). Analysis of risk values modification did not reveal significant differences in dose dependence on the studied factors, including attained age and age at exposure. The study will be continued to investigate in more detail the influence of time-dependent factors on dose dependence, as well as to assess the risk of death from different cellular forms of leukemia.

Roohi Zafar, Muhammad Kamran, Tahir Malik et al.

Random numbers are central to various applications such as secure communications, quantum key distribution theory (QKD), statistics, and other tasks. One of today's most popular generators is quantum random numbers (QRNGs). The inherent randomness and true unpredictability in quantum mechanics allowed us to construct QRNGs that are more accurate and useful than traditional random number generators. Based on different quantum mechanical principles, several QRNGs have already been designed. The primary focus of this paper is the generation and analysis of quantum random numbers based on radioactive decay. In the experimental set, two beta-active radioactive sources, cobalt-60 (Co60) and Strontium-90 (Sr 90), and an ST-360 counter with a Geiger-Muller (GM) tube are used to record the counts. The recorded data was then self-tested by entropy and frequency measurement. Moreover, popular testing technique, the National Institute of Science and Technology (NIST) randomness testing is used, to ensure that the guaranteed randomness meets security standards. The research provides the impact of the nature of the radioactive source, the distance between the counter and sources, and the recording time of the counts on generating quantum random numbers of radioactive QRNGs.

Rafael Guimarães Malanga, Thatiane Alves Pianoschi, Cassiana Viccari et al.

The interaction of radiation with biological tissues may cause some damage. To quantify it, studying cells in vitro is one methodology for analyzing dose deposition in biological tissues because once exposed to radiation, different methods can quantify the biological damage. However, biological tissue culture exposure forms mostly employ high-energy beams (MeV). Thus, this study aims to characterize the radiation field from X-ray equipment using thermoluminescent dosimeters (TLD), to establish an in vitro irradiation protocol of breast cancer and glioblastoma cells for low energies. First, the central axis alignment test was performed to ensure the equipment followed the Normativa IN 90. Then the variation of radiation intensity was analyzed for a 5 x 5 cm² field at distances between 30 and 90 cm from the focal point to the detector. Subsequently, TLD immersed in breast cancer and glioblastoma cellular media were irradiated in a 106 kV and 71 mAs beam to evaluate the dose in cellular media. Simulations were performed with the PENELOPE code to compare with experimental results. The result of the central axis alignment showed that the equipment complies with the current Normativa. The dose distributions for the evaluated distances were more homogeneous for the 40 cm distance, with a standard deviation of 1.7% and 0.9% of the distributions obtained with the TLD and simulation, respectively. Thus, the irradiation field for low energy beams was characterized for a 5 x 5 cm² field for 106 kV and 71 mAs beams at a DFS of 40 cm.

Fernando Rodrigues, Arnie Nolasco, Luiz Cláudio Meira Belo et al.

Total body irradiation (TBI) is a treatment modality of radiotherapy. It can be used for immunosuppression of transplanted patients or for metastatic protocols. In this study, TBI was performed using the anthropomorphic Alderson-Rando phantom filled with thermoluminescent dosimeters (TLDs) and irradiated with a 6 MV photon beam from the Elekta linear accelerator in two different setups, one at the hospital São Francisco, BH, MG and second at the hospital Santa Casa in Lavras, MG. The dose distribution in the left and right lungs was estimated, analyzed, and compared with results from the literature. Our results showed that dose homogeneity is more adequate with dual-field irradiation.

Andre Gonçalves Prospero, Ana Carolina Ferreira, Diana Rodrigues Pina et al.

The Technical Report Series 398 (TRS-398), Electron Dosimetry Working Party (EWDP), and Task Group 51 (TG 51) are the most important protocols for reference dosimetry. In the case of electron beam reference dosimetry, these protocols recommend using parallel-plate ionization chambers for beams with R50 values below specific thresholds. However, recent papers suggested using cylindrical chambers for reference dosimetry of all electron beam energies. Here we compared different protocols using a cylindrical chamber with the recommendations of using a parallel-plate chamber and the TRS-398 formalism for the dosimetry of several electron beam energies.  We employed electron beams with nominal energies of 4, 6, 9, 12, and 15 MeV of a Varian 2100C linear accelerator, an Exradin A12, and an Exradin P11 chamber for the analysis. The results showed differences below 3% when comparing the cylindrical chamber and alternative protocols with the parallel-plate chamber and the TRS-398 formalism for electron beams reference dosimetry. These results can bring confidence in using a cylindrical chamber for reference electron beam dosimetry, which can make the electron beam dosimetry procedure simpler and faster.

Nayara Alves Severo, Cilene Souza Barreto, Maria de Lourdes Meirelles Noviello et al.

Ionizing radiation has been used for the treatment of various diseases for over a century, including chronic inflammatory diseases and cancer. The relationship between radiation and asthma are contradictory; while some authors associate radiation exposure with the development of the disease, others report an attenuation of asthma in response to radiation. Asthma is a chronic inflammatory disease and represents a worldwide public health problem with a high number of deaths. In the present study, we have conducted an investigation of the effects of radiation with 10 doses of 0.5Gy of Co60 and/or moderate lung training of mice with ovalbumin-induced asthma. For this purpose, we have compared six experimental groups of mice: 1-Saline (non-irradiated, sedentary and saline); 2- IR (irradiated and sedentary); 3- OVA (non-irradiated, sedentary and asthma); 4- OVA+IR (irradiated, asthma and sedentary); 5- OVA+IR+MT (irradiated, asthma and moderate training -TM); 6- OVA+MT (asthma and moderate training). The results indicate that radiation and moderate training reduced inflammatory parameters significantly both in BALF cells and in mucus production, thus attenuating the asthma symptoms.

Maria Lugaro, Benoit Côté, Marco Pignatari et al.

Radioactive nuclei are the key to understanding the circumstances of the birth of our Sun because meteoritic analysis has proven that many of them were present at that time. Their origin, however, has been so far elusive. The ERC-CoG-2016 RADIOSTAR project is dedicated to investigating the production of radioactive nuclei by nuclear reactions inside stars, their evolution in the Milky Way Galaxy, and their presence in molecular clouds. So far, we have discovered that: (i) radioactive nuclei produced by slow ($^{107}$Pd and $^{182}$Hf) and rapid ($^{129}$I and $^{247}$Cm) neutron captures originated from stellar sources - asymptotic giant branch (AGB) stars and compact binary mergers, respectively - within the galactic environment that predated the formation of the molecular cloud where the Sun was born; (ii) the time that elapsed from the birth of the cloud to the birth of the Sun was of the order of 10$^7$ years, and (iii) the abundances of the very short-lived nuclei $^{26}$Al, $^{36}$Cl, and $^{41}$Ca can be explained by massive star winds in single or binary systems, if these winds directly polluted the early Solar System. Our current and future work, as required to finalise the picture of the origin of radioactive nuclei in the Solar System, involves studying the possible origin of radioactive nuclei in the early Solar System from core-collapse supernovae, investigating the production of $^{107}$Pd in massive star winds, modelling the transport and mixing of radioactive nuclei in the galactic and molecular cloud medium, and calculating the galactic chemical evolution of $^{53}$Mn and $^{60}$Fe and of the p-process isotopes $^{92}$Nb and $^{146}$Sm.

Evgeny Akhmedov, Alexei Y. Smirnov

Spatial separation of the wave packets (WPs) of neutrino mass eigenstates leads to decoherence and damping of neutrino oscillations. Damping can also be caused by finite energy resolution of neutrino detectors or, in the case of experiments with radioactive neutrino sources, by finite width of the emitted neutrino line. We study in detail these two types of damping effects using reactor neutrino experiments and experiments with radioactive $^{51}$Cr source as examples. We demonstrate that the effects of decoherence by WP separation can always be incorporated into a modification of the energy resolution function of the detector and so are intimately entangled with it. We estimate for the first time the lengths $σ_x$ of WPs of reactor neutrinos and neutrinos from a radioactive $^{51}$Cr source. The obtained values, $σ_x = (2\times 10^{-5} - 1.4\times 10^{-4})$ cm, are at least six orders of magnitude larger than the currently available experimental lower bounds. We conclude that effects of decoherence by WP separation cannot be probed in reactor and radioactive source experiments.

P. D. O'Malley, T. Ahn, D. W. Bardayan et al.

We report here on the recent upgrade of the TwinSol radioactive nuclear beam (RNB) facility at the University of Notre Dame. The new TriSol system includes a magnetic dipole to provide a second beamline and a third solenoid which acts to reduce the size of the radioactive beam on target.

E.A. Shishkina, V.I. Starichenko, E.R. Valeeva et al.

Luiz Gonzaga de Freitas Neto, Luciano Ondir Freire, Adimir dos Santos et al.

Operating costs of merchant ships, related to fuel costs, has led the naval industry to search alternatives to the current technologies of propulsion power. A possibility is to employ nuclear reactors like the Russian KLT-40S, which is a pressurized water reactor (PWR) and has experience on civilian surface vessels. However, space and weight are critical factors in a nuclear propulsion project, in addition to operational safety and costs. This work aims at comparing molten salt reactors (MSR) with PWR for merchant ship propulsion. The present study develops a qualitative analysis on weight, volume, overnight costs, fuel costs and nuclear safety. This work compares the architecture and operational conditions of these two types of reactors. The result is that MSR may produce lower amounts of high-activity nuclear tailings and, if it adopts the 233U-thorium cycle, it may have lower risks of proliferating nuclear weapons. Besides proliferation issues, this 4th generation reactor may have lower weight, occupy less space, and achieve the same levels of safety with less investment. Thus, molten salt regenerative reactors using the 233U-thorium cycle are potential candidates for use in ship propulsion.

Natália Fonseca Taveira, Frederico Guimarães, Talita Santos et al.

The Quadrilátero Ferrífero (QF) is one of the most well-known metallogenetic provinces in the world and has its geological context well studied since the end of the 17th century. The Serra do Gandarela is positioned in the northeast of the QF and is supported by units of the Minas Supergroup. The Moeda Formation (MF) in the Serra do Gandarela hosts an uranium (U) occurrence which was recently characterized in terms of mineralogical context. Uraninite, coffinite and brannerite are the main U minerals present. It is expected that mineralogy and lithology contribute to radon emanation and exhalation, the radon (Rn) transport from the soil to the atmosphere. In this work, the Rn exhalation was correlated to the lithological types. Samples from the MF conglomerates and Nova Lima group schists were collected from the Serra do Gandarela. Rn exhalation measurements were performed on the samples with AlphaGUARD detector. These values were compared to the U content of samples obtained via INAA. The result of INAA was more expressive in the MF conglomerate sample from the NUCLEBRÁS drillcore, with a U concentration value of 24 µg.g-1. The sample that had the highest average exhalation rate was also the same. The lowest value presented for both U concentration and average exhalation rate was shale, which were, 2 µg.g-1 and 180 Bq.m-3, respectively. The results are relevant for exploration and mining activities, during which Rn can accumulate in galleries. Additionally, the knowledge of the characteristic emanometric can be an important tool for geological and environmental studies.

Guilherme Cavalcante de Albuquerque Souza, Rodrigo Modesto Gadelha Gontijo, Juliana Batista da Silva et al.

Positron emission tomography (PET) is an important molecular image modality and its application on preclinical research has increased during last decades. Thus, in laboratory practice, it is important to implement a quality control of the equipment, since intrinsic factors influence the image quality. The objective of this work was to perform and implement spatial resolution tests for the small animal PET scanner of the Molecular Imaging Laboratory, LIM/CDTN. Empirically, spatial resolution of a PET scanner can be determined from the measurement of point or linear sources and FWHM (full width half maximum) analysis of the respective linear profiles. In this work, a point source of 22Na and a hot rod style phantom filled with 18F-FDG solution were used. Acquisition and reconstruction of images were performed with the LabPET 1.12.1 software, provided by the equipment manufacturer. Image reconstruction parameters followed the LIM standard protocol: MLEM-3D algorithm, 20 iterations, no high resolution mode, no attenuation or scatter corrections, no post-filtering. PeakFit® and Amide softwares were used to perform images post-processing. The results indicate that the scanner has an adequate spatial resolution and its value is compatible with values reported in international studies performed on similar equipments.

S. Michelle Bourret, Edward M. Kwicklis, Dylan R. Harp et al.

David McKeen, Maxim Pospelov, Nirmal Raj

We show that in a special class of dark sector models, the hydrogen atom can serve as a portal to new physics, through its decay occurring in abundant populations in the Sun and on Earth. The large fluxes of hydrogen decay daughter states can be detected via their decay or scattering. By constructing two models for either detection channel, we show that the recently reported excess in electron recoils at XENON1T could be explained by such signals in large regions of parameter space unconstrained by proton and hydrogen decay limits.