Search Results (36)

COMCUBE-S (Compton Telescope CubeSat Swarm) is a proposed mission aimed at understanding the radiation mechanisms of ultra-relativistic jets from Gamma-Ray Bursts (GRBs). It consists of a swarm of 16U CubeSats carrying a state-of-the-art Compton polarimeter and a bismuth germanium oxide (BGO) spectrometer to perform timing, spectroscopic and polarimetric measurements of the prompt emission from GRBs. The mission is currently in a feasibility study phase (Phase A) with the European Space Agency to prepare an in-orbit demonstration. Here, we present the simulation work used to optimise the design and operational concept of the microsatellite constellation, as well as estimate the mission performance in terms of GRB detection rate and polarimetry. We used the MEGAlib software to simulate the response function of the gamma-ray instruments, together with a detailed model for the background particle and radiation fluxes in low-Earth orbit. We also developed a synthetic GRB population model to best estimate the detection rate. These simulations show that COMCUBE-S will detect about 2 GRBs per day, which is significantly higher than that of all past and current GRB missions. Furthermore, simulated performance for linear polarisation measurements shows that COMCUBE-S will be able to uniquely distinguish between competing models of the GRB prompt emission, thereby shedding new light on some of the most fundamental aspects of GRB physics. Full article

Cancer poses a global challenge, affecting millions of people and placing a significant burden on families and healthcare systems. Chemotherapy, radiotherapy, hormone therapy, and immunotherapy are commonly used for cancer treatment; their side effects can be severe. Photothermal therapy (PTT) has emerged as a promising alternative due to its minimal invasiveness and high efficiency. In this study, graphene oxide (GO) was synthesized and functionalized to obtain nitrogen-doped graphene oxide (NGO) and boron-doped graphene oxide (BGO) via a hydrothermal process, aiming to use them as photoactive agents (PAs) in PTT. Atomic force microscopy (AFM) analysis revealed that GO, BGO, and NGO exhibit monolayer atomic structures. Spectroscopic analyses confirmed the presence of oxygen and carbon in all samples, along with successful boron and nitrogen doping in BGO and NGO, respectively. Cytotoxicity assays yielded half-maximal inhibitory concentrations (IC₅₀) of 1025.26 μg/mL for GO, 2695.03 μg/mL for BGO, and 1319.81 μg/mL for NGO. Photothermal experiments were conducted using a 635 nm light source with an intensity of 65.5 mW/cm², resulting in temperature thresholds of 44.87 °C for GO, 48.36 °C for NGO, and 55.91 °C for BGO. Anticancer assays were performed using the T-47D breast cancer cell line, demonstrating tumor cell elimination rates of 97.93% for GO, 98.54% for BGO, and 97.98% for NGO, underscoring their efficacy as PAs. Density functional theory (DFT) simulations were carried out to determine the absorbance coefficient as a function of doping percentage. The results revealed that increased doping enhances light absorbance and, consequently, the photothermal response, as higher absorbance at the irradiation wavelength leads to greater energy absorption and temperature elevation. Full article

Microcalcifications (HAp, CaCO₃, and CaC₂O₄) in breast tissue may indicate malignancy. Early-stage breast cancer diagnosis may benefit from the clinical application of dual-energy techniques. Dual-energy cone-beam computed tomography (CBCT) could strongly contribute to an accurate diagnosis, especially in dense breasts. This study focused on photon-counting detector alternatives to the standard cesium iodide (CsI) that CBCT currently relies on and investigated potential advantages over the employed CsI scintillators. Denser detector materials with a higher effective atomic number than CsI could improve image quality. A micro-CBCT was simulated in GATE using seven different detector configurations (CsI, bismuth germanate (BGO), lutetium oxyorthosilicate (LSO), lutetium–yttrium oxyorthosilicate (LYSO), gadolinium aluminum gallium garnet (GAGG), lanthanum bromide (LaBr₃), and cadmium zinc telluride (CZT)) and four breast tissue phantoms containing microcalcifications of both type I and type II. The dual-energy methodology was applied to planar and tomographic acquisition data. Tomographic data were reconstructed using filtered backprojection (FBP) and the ordered-subsets expectation-maximization (OSEM) algorithm. Image quality was measured using contrast-to-noise ratio (CNR) values. Both monoenergetic and polyenergetic models were considered. CZT and GAGG crystals presented higher CNR values than CsI. HAp microcalcifications exhibited the highest CNR values, which, when accompanied by OSEM, could be distinguished for classification. Detector configurations based on CZT or GAGG crystals could be adequate alternatives to CsI in dual-energy CBCT. Full article

Background/Objectives: Ingestion of galactooligosaccharides (GOSs) or GOS mixtures has been purported to improve exercise-induced gastrointestinal (GI) distress and post-exercise recovery. However, the effects have not been explored in recreationally trained endurance athletes. This triple-blind randomised controlled trial, therefore, investigated whether 12 weeks of B-GOS^® supplementation affects gastrointestinal comfort and psychological wellbeing in recreational athletes. Methods: Eighteen physically active individuals (12 males, 8 females, 44 ± 14 years, 1.7 ± 0.1 m and 73 ± 14 kg) volunteered for this study. Participants were assigned to independent groups in a placebo-controlled, triple-blind manner via stratified randomisation. A 20 min run at 80% VO_2max was completed, with measures for GI distress and Competitive State Anxiety Inventory-2 questionnaire (CSAI-2) pre- and post-exercise. A 12-week supplementation period then ensued, where participants ingested either 3.65 g of B-GOS or an appearance-matched maltodextrin placebo. During this time, physical activity levels (IPAQ-7), general stress (REST-Q), mental wellbeing (WEMWBS), and sleep (core consensus sleep diary) were measured at regular time points. Results: There were no significant differences in VO_2max (p = 0.437), GI discomfort (p = 0.227), or CSAI-2 (p = 0.739–0.954) from pre- to post-exercise at any time point or between conditions. Over the 12 weeks there were no significant differences between B-GOS and placebo in IPAQ-7 (p = 0.144–0.723), REST-Q (p = 0.282–0.954), WEMWBS (B-GOS pre = 51 ± 10, post = 53 ± 7; PLA pre = 51 ± 4, post 54; p = 0.862), or sleep (p = 0.065–0.992). The linear mixed model suggests that some may benefit on an individual level in terms of WEMWBS, general stress score, recovery-related scores, sleep, and sport-specific recovery score. Conclusions: There were no group benefits of B-GOS supplementation compared with placebo, although the individual variation may warrant further research in larger sample sizes and longer-duration studies. Full article

Developing detectors to enhance the timing resolution of positron emission tomography scanners can help reduce radioactive doses absorbed by patients and improve spatial resolution in medical imaging. Time resolution may be enhanced in heterostructures comprising a heavy scintillator for attenuation of 511 keV γ-quanta, as well as a fast scintillator converting recoiled electrons from the heavy scintillator to prompt light photons. In this study, ZnO films as fast scintillators with different thicknesses were obtained on substrates of a heavy bismuth germanate (Bi₄Ge₃O₁₂, BGO) scintillator using several film preparation techniques, such as spray-coating, drop-casting, and spin-coating. The design of heterostructures combined the key advantage of a low-cost film preparation technique with environmentally friendly and available precursors. This work proposes synthesis methods of highly nanocrystalline ZnO films on BGO, where a film thickness ranges from 6 to 18 μm. All ZnO studied films exhibit exciton luminescence peaked in UV (353 nm) and defect luminescence in the green (657 nm) range under 325 nm excitation. The best coincidence time resolution of 158 ± 8 ps was obtained with BGO@ZnO heterostructures fabricated by the spray-coating. The proposed approach allowed obtaining BGO@ZnO heterostructures for potential use as ultrafast scintillation detectors. Full article

With the advent of novel scintillators featuring higher atomic numbers and enhanced radiation hardness, these materials exhibit potential applications under high-dose-rate irradiation. In this work, we systematically compared the photon output characteristics of ten mainstream or emerging inorganic scintillators under high-dose-rate irradiation with low-energy (0.1–1.7 MeV) electrons or protons. Initially, under electron irradiation among ~0.1 to ~50 rad/s, responses exhibited saturation trends to varying degrees, with their variations conforming to the saturation model proposed. However, under proton irradiation among ~5 rad/s to ~150 rad/s, responses exhibited sigmoidal trends due to competition between radiation-induced defects and luminescence centers. Through dynamic derivation of carriers and them, a triple-balance model that demonstrated close agreement with such variations was established. Subsequently, energy-dependent responses under proton irradiation exhibited marked nonlinearity, which were well fitted by Birks’ law, confirming the validity of our measurements. In contrast, electron-induced responses remained nearly linear with increasing energy. Then, after high-dose-rate and prolonged irradiation, BGO revealed highest response degradation, while YAG(Ce) demonstrated most radiation-damage resistance. Moreover, Ce-doped scintillators displayed higher afterglow levels after prolonged irradiation, particularly for YAG(Ce). In summary, these experimental analyses can provide critical guidance for material selection and effective calibration of scintillator detectors operating under high-dose-rate radiation from charged particles. Full article

In this study, Lu_2.5Y_0.5(Al_2.5Ga_2.5)O₁₂ (LuYAGG) single-crystal scintillators doped with terbium ions (Tb³⁺) at concentrations of 0.5, 1, 5, and 10 mol% were successfully synthesized using the floating zone method. The structural, optical, photoluminescence (PL), and scintillation properties of the Tb³⁺-doped crystals were systematically investigated with a focus on their potential for high-performance scintillator applications. X-ray diffraction (XRD) confirmed the formation of a pure garnet phase without any secondary phases, indicating the successful incorporation of Tb³⁺ into the LuYAGG lattice. Optical transmittance spectra revealed high transparency in the visible range. Photoluminescence measurements showed characteristic Tb³⁺ emission peaks, with the strongest green emission observed from the ⁵D₄ → ⁷F₅ transition, particularly for the 5 mol% sample. The PL decay curves further confirmed that this concentration offers a favorable balance between radiative efficiency and minimal non-radiative losses. Under γ-ray excitation, the 5 mol% Tb³⁺-doped crystal exhibited the highest light yield, surpassing the performance of other concentrations and even outperforming Bi₄Ge₃O₁₂ (BGO) in relative comparison, with an estimated yield of approximately 60,000 photons/MeV. Scintillation decay time analysis revealed that the 5 mol% sample also possessed the fastest decay component, indicating its superior capability for radiation detection. Although 10 mol% Tb³⁺ still showed good performance, slight quenching effects were observed, while lower concentrations (0.5 and 1 mol%) suffered from longer decay and lower emission efficiency due to limited activator density. These findings clearly identify with 5 mol% Tb³⁺ as the optimal dopant level in LuYAGG single crystals, offering a synergistic combination of high light yield and excellent optical transparency. This work highlights the strong potential of LuYAGG:Tb³⁺ as a promising candidate for the next-generation scintillator materials used in medical imaging, security scanning, and high-energy physics applications. Full article

In this study, the luminescence efficiency of a crystal-form barium fluoride (BaF₂) inorganic scintillator was assessed for medical imaging applications. For the experiments, we used a typical medical X-ray tube (50–140 kVp) for estimating the absolute luminescence efficiency (AE). Furthermore, we examined the spectral matching of the inorganic scintillator with a series of optical detectors. BaF₂ showed a higher AE than cerium fluoride (CeF₃), comparable to that of commercially available bismuth germanate (Bi₄Ge₃O₁₂-BGO), but lower than that of the gadolinium orthosilicate (Gd₂SiO₅:Ce-GSO:Ce) inorganic scintillator. The maximum AE of BaF₂ was 2.36 efficiency units (EU is the S.I. equivalent μWm⁻²/(mR/s) at 140 kVp, which is higher than that of the corresponding fluoride-based CeF₃ (0.8334 EU)) at the same X-ray energy. GSO:Ce and BGO crystals, which are often integrated in commercial positron emission tomography (PET) scanners, had AE values of 7.76 and 3.41, respectively. The emission maximum (~310 nm) of BaF₂ is adequate for coupling with flat-panel position-sensitive (PS) photomultipliers (PMTs) and various photocathodes. The luminescence efficiency results of BaF₂ were comparable to those of BGO; thus, it could possibly be used in medical imaging modalities, considering its significantly lower cost. Full article

The present paper introduces the so-called scintillator footprints, consisting of plots showing XRF-escape peaks and their relative emission intensities in the energy range of interest for nuclear medicine SPECT and PET. A footprint describes the suitability of a scintillator for quantitative investigation with the best possible detectability. Sixteen scintillation materials have been identified in the literature, characterized by effective atomic numbers Z_eff ranging between 22 and 75. The footprints of NaI:Tl and BGO, confirm the best suitability for quantitative spectral analysis in SPECT and PET, at 140.5 keV and 511 keV, respectively. Moreover, for the low-Zeff scintillators like CaF2 and CMSM, the XRF-escape effect is to predict irrelevant even at 140.5 keV due to the small energy value of X-ray fluorescence. Full article

The long-term afterglow of scintillators is an important aspect, especially when the light signal from a scintillator is evaluated in the current mode. Scintillators used for radiation detection exhibit an afterglow, which usually comes from multiple components that have different decay times. A high level of afterglow usually has a negative influence on the detection parameters for the energy resolution in spectrometry measurements or X-ray and neutron imaging. The paper deals with the long-term afterglow of some types of scintillators, which is more significant for integral measurement when the current is measured in a photodetector. The range of decay times studied was in the order of tens of seconds to days. Seven types of scintillators were examined: BGO, CaF₂(Eu), CdWO₄, CsI(Tl), LiI(Eu), NaI(Tl), and plastic scintillator. The scintillators were excited by gamma-ray radiation. After irradiation, the detection unit, along with the scintillator, was moved to a laboratory where the anode current of the photomultiplier tube was measured using a picoammeter for at least a day. The measurements showed that CdWO₄ and plastic scintillators have relatively low long-term afterglow signals in comparison to the other scintillators studied. Full article

Bismuth germanate (Bi₄Ge₃O₁₂, BGO) is a widely used optical sensing material with a high electro-optic coefficient, ideal for optical electric field sensors. Achieving high precision in electric field sensing requires fabricating optical waveguides on BGO. Traditional waveguide writing methods face challenges with this material. This study explores using femtosecond laser writing technology for preparing waveguides on BGO, leveraging ultrafast optical fields for superior material modification. Our experimental analysis shows that a cladding-type waveguide, written with a femtosecond laser at 200 kHz repetition frequency and 10.15 mW average power (pulse energy of 50.8 nJ), exhibits excellent light-guiding characteristics. Simulations of near-field optical intensity distribution and refractive index variations using the refractive index reconstruction method demonstrate that the refractive index modulation ensures single-mode transmission and effectively confines light to the core layer. In situ refractive index characterization confirms the feasibility of fabricating a waveguide with a refractive index reduction on BGO. The resulting waveguide has a loss per unit length of approximately 1.2 dB/cm, marking a successful fabrication. Additionally, we design an antenna electrode, analyze sensor performance indicators, and integrate a preparation process plan for the antenna electrode. This achievement establishes a solid experimental foundation for future studies on BGO crystal waveguides in electric field measurement applications. Full article

The aim of this study was to experimentally assess the luminescence efficiency of a cerium fluoride (CeF₃) inorganic scintillator in crystal form as a possible alternative to high-luminescence but hygroscopic cerium bromide (CeBr₃). The experiments were performed under typical diagnostic radiology X-rays (50–140 kVp). Parameters such as the crystal’s absolute luminescence efficiency (AE) and the spectral matching with a series of optical detectors were examined. The replacement of bromine with fluorine appeared to drastically reduce the AE of CeF₃ compared to CeBr₃ and other commercially available inorganic scintillators such as bismuth germanate (Bi₄Ge₃O₁₂-BGO). CeF₃ reaches a maximum luminescence efficiency value of only 0.8334 efficiency units (EUs) at 140 kVp, whereas the corresponding values for CeBr₃ and BGO were 29.49 and 3.41, respectively. Furthermore, the emission maximum (at around 313 nm) moved towards the lower part of the visible spectrum, making CeF₃ suitable for spectral coupling with various photocathodes and photomultipliers applied in nuclear medicine detectors, but completely unsuitable for spectral matching with CCDs and CMOS. The obtained luminescence efficiency results denote that CeF₃ cannot be applied in medical imaging applications covering the range 50–140 kVp; however, examination of its luminescence output in the nuclear medicine energy range (~70 to 511 keV) could reveal possible applicability in these modalities. Full article

The combination of high-density, high-time-resolution inorganic scintillation crystals such as Lutetium Yttrium Oxyorthosilicate (LYSO), Yttrium Orthosilicate (YSO) and Bismuth Germanate (BGO) with Silicon Photomultiplier (SiPM) sensors is widely employed in medical imaging, particularly in Positron Emission Tomography (PET), as well as in modern particle physics detectors for precisely timing sub-detectors and calorimeters. During the assembly of each module, following individual component testing, the crystals and SiPMs are bonded together using optical glue and enclosed in a light-tight, temperature-controlled cooling box. After integration with the readout electronics, the bonding is initially tested. The final readout electronics typically comprise Application-Specific Integrated Circuits (ASICs) or low-power Analog-to-Digital Converters (ADCs) and amplifiers, designed not to heat up the temperature-sensitive SiPM sensors. However, these setups are not optimal for testing the optical bonding. Specific setups were developed to test the LYSO + SiPM modules that are already bonded but not enclosed in a box. Through large data collection, small deviations in bonding can be detected if the SiPMs and LYSOs have been thoroughly tested before our measurement. The Monte Carlo simulations we used to study how parameters—which are difficult to measure in the laboratory (LYSO absorption length, refractive index of the coating)—affect the final result. Our setups for particle physics and PET applications are already in use by research institutes and industrial partners. Full article

Cone-beam computed tomography (CBCT) has emerged in recent years as an adequate alternative to mammography and tomosynthesis due to the several advantages over traditional mammography, including its ability to provide 3D images, its reduced radiation dose, and its ability to image dense breasts more effectively and conduct more effective breast compressions, etc. Furthermore, CBCT is capable of providing images with high sensitivity and specificity, allowing a more accurate evaluation, even of dense breasts, where mammography and tomosynthesis may lead to a false diagnosis. Clinical and experimental CBCT systems rely on cesium iodine (CsI:Tl) scintillators for X-ray energy conversion. This study comprises an investigation among different novel CBCT detector technologies, consisting either of scintillators (BGO, LSO:Ce, LYSO:Ce, LuAG:Ce, CaF₂:Eu, LaBr₃:Ce) or semiconductors (Silicon, CZT) in order to define the optimum detector design for a future experimental setup, dedicated to breast imaging. For this purpose, a micro-CBCT system was adapted, using GATE v9.2.1, consisting of the aforementioned various detection schemes. Two phantom configurations were selected: (a) an aluminum capillary positioned at the center of the field of view in order to calculate the system’s spatial resolution and (b) a breast phantom consisting of spheres of different materials, such that their characteristics are close to the breast composition. Breast phantom contrast-to-noise ratios (CNRs) were extracted from the phantom’s tomographic images. The images were reconstructed with filtered back projection (FBP) and ordered subsets expectation-maximization (OSEM) algorithms. The semiconductors acted satisfactorily in low-density matter, while LYSO:Ce, LaBr₃:Ce, and LuAG:Ce presented adequate CNRs for all the different spheres’ densities. The energy converters that are presented in this study were evaluated for their performance against the standard CsI:Tl crystal. Full article

Human exposure to dicarbonyls occurs via ingestion (e.g., food), inhalation (e.g., electronic cigarettes) and dysregulation of endogenous metabolic pathways (e.g., glycolysis). Dicarbonyls are electrophiles able to induce carbonylation of endogenous substrate. They have been associated with the onset and progression of several human diseases. Several studies have advocated the use of dicarbonyl binders as food preservatives or as drugs aimed at mitigating carbonylation. This study presents the setup of an easy and cheap assay for the screening of selective and potent dicarbonyl binders. The method is based on the incubation of the candidate molecules with a molecular probe. The activity is then determined by measuring the residual concentration of the molecular probe over time by liquid chromatography (LC). However, the naturally occurring dicarbonyls (e.g., glyoxal, methylglyoxal) are not appealing as probes since they are hard to separate and detect using the most popular LC variants. Benzylglyoxal (BGO) was therefore synthesized and tested, proving to be a convenient probe that allows a direct quantification of residual dicarbonyls by reversed phase LC without derivatization. The method was qualified by assessing the binding ability of some molecules known as binders of natural occurring dicarbonyls, obtaining results consistent with literature. Full article