High-energy Rays Research Articles

Gamma rays excited radioluminescence tomographic imaging

BackgroundRadionuclide-excited luminescence imaging is an optical radionuclide imaging strategy to reveal the distributions of radioluminescent nanophosphors (RLNPs) inside small animals, which uses radioluminescence emitted from RLNPs when excited by high energy rays such as gamma rays generated during the decay of radiotracers used in clinical nuclear medicine imaging. Currently, there is no report of tomographic imaging based on radioluminescence.MethodsIn this paper, we proposed a gamma rays excited radioluminescence tomography (GRLT) to reveal three-dimensional distributions of RLNPs inside a small animal using radioluminescence through image reconstruction from surface measurements of radioluminescent photons using an inverse algorithm. The diffusion equation was employed to model propagations of radioluminescent photons in biological tissues with highly scattering and low absorption characteristics.ResultsPhantom and artificial source-implanted mouse model experiments were employed to test the feasibility of GRLT, and the results demonstrated that the ability of GRLT to reveal the distribution of RLNPs such as Gd2O2S:Tb using the radioluminescent signals when excited by gamma rays produced from 99mTc.ConclusionsWith the emerging of targeted RLNPs, GRLT can provide new possibilities for in vivo and noninvasive examination of biological processes at cellular levels. Especially, combining with Cerenkov luminescence imaging, GRLT can achieve dual molecular information of RLNPs and nuclides using single optical imaging technology.

Ultrasmall Pt Clusters Reducing Radiation-Induced Injuries via Scavenging Free Radicals.

High energy ionizing radiation was widely used in medical diagnosis and cancer radiation therapy. The high dose of X ray or γ ray can cause the damage of cancerous tissue as well as healthy tissue during therapy. Therefore, it is urgent to develop chemical agents to protect the healthy tissue from high energy ray invasion. Here, the ultrasmall Pt clusters were employed as the anti-radiation agents for protecting healthy cells and improving survival rate of irradiated mice. It was found that Pt clusters can reduce the DNA damages in irradiated cells. In vivo experiments show that the Pt clusters treatment can improve the survival rate of irradiated mice up to 30%. As a contrast, only-irradiated mice without Pt clusters treatment completely died after 15 days. The detailed biological experiments showed that Pt clusters can recover the bone marrow DNA level and superoxide dismutase activities via scavenging free radicals. Importantly, the ultrasmall Pt clusters can be excreted rapidly by kidney and do not cause long-term toxicity.

The EEE project – Science in schools: state and results

The Extreme Energy Events (EEE) project is an extended array for cosmic rays survey. It was conceived by Antonino Zichichi and supported by the Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi” with the collaboration of the European Organization for Nuclear Research (CERN), of the Istituto Nazionale di Fisica Nucleare (INFN) and of the Italian Ministry of Education, University and Research (MIUR). This experiment is aimed to study cosmic rays of extreme high energy, and related phenomena. To achieve this goal, a network of nearly 50 muon telescopes has been installed in high schools, distributed throughout the Italian territory, either as single stations or clusters. During the second coordinated run of data taking, which ended in May 2016, 25 billion muon tracks were detected and reconstructed. This huge amount of data, allows us to undertake various studies: the dependence of the local muon flux on solar activity; the sky anisotropy on sub-TeV scale; event correlations, due to EAS, between clustered telescopes at distances from a few hundred meters to over a kilometre. The status of the project and some results will be presented.

Using two-photon statistical contribution in the detection of telescopes EUSO

The Extreme Universe Space Observatory onboard Japanese Experiment Module (JEM-EUSO) is the future space observatory will be installed on the International Space Station (ISS) to study the comic rays of ultra high energy (UHECR). The Photo detector module (PDM) of telescope (JEM-EUSO) is characterized by high sensitivity detection that allows you to detect single photons of UV backgraund. The telescope EUSO-Balloon was the first prototype to validate JEM-EUSO chain detection in extreme environmental conditions. The post flight analysis of the efficiency of EUSO-Balloon detection showed that only 30 % of the pixels met the technical requirements for the study of EAS et detection of UV background (required efficiency of photo-detection > 12%). The next prototypes of JEM-EUSO have as their mission the Extensive Air Shower (EAS) detection of UHECR with energies > 1020eV. An requirement for this, it is the validation of the systems trigger, which distinguish this luminescence over background noise UV. These systems trigger requires that all pixels are operational, this means, these pixels must be able to detect events corresponding to one photo-electron (pe) per gate time unit (GTU=2, 5μs). This work is about a method to offset, to some extent, the problem of efficiency loss of detection channels. The formation of a pulse signal corresponding to 1 pe is governed by the Poisson distribution, this means that there are pulses formed by the pil-up of two or more pulses. That may eventually be used to estimate the efficiency of pixels with weak performance.

Cation-substitution induced stable GGAG:Ce3+ ceramics with improved optical and scintillation properties

Among the aluminate garnet materials, cerium doped gadolinium gallium aluminum garnet ceramics (GGAG:Ce) have shown great performance advantages, which suggests their promising applications in medical imaging, high energy rays detection and high power LED lighting. The goal of this work is to raise the thermostability of GGAG:Ce by means of partial Y3+ substitution, and to find out the relationship between the crystal structure and the optical properties. GGAG:Ce3+,xY3+ ceramics were prepared via chemical precipitation, and a combination of sintering in oxygen atmosphere and hot isostatic pressing. In order to identify the detailed crystal structure information, Rietveld refinements were first taken on the XRD patterns. Crystal structure refinements verify the ability of mutual substitution of Y and Ga atoms between the dodecahedron and octahedral sites. The optical, luminescent and scintillation properties have been investigated. Results show that the transmittance of the sample can reach 77% at the emission peak wavelength, while the spectrally corrected light yield value reaches 61,000±1200photons/MeV.

3$\gamma $ Medical Imaging with a Liquid Xenon Compton Camera and $^{44}$Sc Radionuclide

The development of a liquid xenon Compton camera called XEMIS2 (XEnon Medical Imaging System) is a step forward to a new type of medical imaging based on the use of 44Sc radionuclide emitting two annihilation rays and a third high energy ray simultaneously. The single phase TPC (Time Projection Chamber) under construction, containing nearly 200 kg of xenon, is designed to measure most of the Compton interactions in the active area with a sub-millimetre position resolution and a good energy resolution of 4% on 511 keV photopeak. The intersection of the Compton cone surface from the third ray with the line of response from the two annihilation rays allows to localize the radionuclide with a precision (FWHM) of about 1 cm along this line. The large field of view of such a liquid xenon camera combined with the 3 imaging technique will provide a good quality image while keeping the injected activity at a very low level. XEMIS2 will be installed in the Nantes University Hospital in order to demonstrate its capability to image small animals injected with a low activity of only 20 kBq in 20 mn acquisition time. To achieve this goal, a precise measurement of the ionization signal is provided by a pixelized anode, shielded by a Frisch Grid and read out by a low noise front-end electronics. In addition, new cryogenic and purification subsystems have been tested, allowing safe recovery of xenon in liquid phase at flow rates of about 1 ton per hour.

Key physics mechanism of the research reactor based slow positron source

In the world there have been built five reactor based slow positron sources producing very intense beams, of which, the NEPOMUC source generates the highest intensity about 3109 e+/s after updated. The beam intensity depends on the power of the core, the converter material, and the moderator geometry. It is important to have good knowledge of the influencing factors and relevant processes for building a positron source in China Mianyang Research Reactor (CMRR). In this paper, the basic mechanism and several pivotal processes are studied and modeled, including the high energy ray induced fast positron generated in target, the moderation of fast positron to slow positron, the emission of slow positron from surface, the extraction of slow positron from surface to external grid, and finally the focusing and transport by beam optic system. The beam intensity at the end of the solenoid can be deduced as I = Emth 12, where 1 is the slow positron extraction efficiency from moderators, 2 is the efficiency of lens extraction and solenoid transportation, and Emth is the slow positron emission rate from surface. The value of Emth can be expressed as Emth= AP 2L+e+pbmod, where A is the effective surface area of the moderator, P is the generating rate of the fast positron in unit volume, L+ is the slow positron diffusion length, e+ is the branching ratio of surface positron ( 0.25), i.e. the ratio of positrons reaching the surface to that emitted freely, pbmod ( 0.4) is the probability of the emitted moderated positron. Therefore, attention should be paid to the values of P, L+, 2 and A to enhance the beam intensity. P is in proportion to the neutron absorption rate by cadmium, which requires higher neutron flux of incidence. L+ is sensitive to the moderator material and its annealing condition. For the well annealed single crystal tungsten, the value of L+ is about 100 nm, while for that annealed at 1600 ℃, it decreases to only 40 nm. The value of 1 is related to the moderator depth/width ratio, the extraction voltage, and the moderator back layout. Although deeper ring can enlarge the moderator area A, the average extraction efficiency 1 decreases obviously. Considering the product of 1 and A, the recommended depth/width ratio is 3 : 1. Validations are performed by employing two types of experimental results, including several isotope slow positron sources and the PULSTAR reactor based source. The calculated efficiencies of isotope sources match well with the experimental measured results, which verifies our basic model and parameters. With these parameters and models, the intensity of PULSTAR reactor based positron source at system exit is calculated to be 5.8108e+/s, which matches well with the reported measured value of (0.5-1.1)109e+/s. Some suggestions are made and will be considered in our future design of positron source.

Rac1 is a potential target to circumvent radioresistance.

Radiation therapy is a main treatment for many types of cancer that uses high-energy rays to destroy cancer cells. The most types of radiation commonly used for cancer treatment include X-rays, gamma rays and charged particles.

Recent advances in rare earth scintillation crystals

Rare earth scintillation crystals act as an important media of radiation detection that could convert high-energy rays or high-energy particles to ultraviolet/visible fluorescence pulse. From the perspective of the periodic table, the rare earth scintillation crystals can be divided into rare earth halide and rare earth oxide compounds. In this review, we summarize the basic scintillation properties and crystallographic structure characteristics of some typical rare earth scintillation crystals. Rare earth ions exhibit excellent luminescent properties due to their unique 4 f electronic structure. Among the lanthanide ions, Ce3+, Pr3+, Eu2+ are chosen as efficient activator ions since they usually show spin- and parity-allowed 5 d ® 4 f transitions. The 4 f orbits of rare earth ions are shielded by filled 5 s and 5 p shells, while 5 d orbits are strongly affected by the surrounding without any shielding effect. The scintillation properties are therefore determined by the composition and structure of rare earth scintillation crystals. On the other hand, some rare earth ions, such as Y3+, La3+and Lu3+, are optically inactive, which can be regard as the ideal chemical compositions of matrix materials. An insight into the rare earth scintillation crystals is provided from the view of composition design and bulk crystal growth. We also discuss the patent protection of rare earth scintillation crystals in China. Future prospects of rare earth scintillation crystals have been briefly mentioned.

Lorentz Invariance Violation: Modification of the Compton Scattering and the GZK Cutoff and Other Effects

This paper deals with the violation of Lorentz symmetry. The approach is based on Compton scattering which becomes modified due to a modified dispersion relation arising from a minimum spacetime cut off as in modern Quantum Gravity approaches. With this amendment, we find that two high-energy rays of different energies develop a time-lag. This time separation becomes prominent when the energies of the considered photons is ≥ 1GeV. Extending our approach to gamma rays of cosmic origin we predict that they undergo innumerable such scattering processes before reaching us. Therefore, it accounts for the time-lag phenomena of gamma ray bursts (GRB)’s which have been claimed to be observed. Also, we find that resorting to the modified Snyder-Sidharth Hamiltonian it is possible to extend the GZK cut off beyond its normal limit, 1020eV. Some observations of ultra high energy cosmic rays support this. This extends the limits of special theory of relativity.

An idea for the future proton detection of (p,2p) reactions with the R3B set-up at FAIR

The R3B Collaboration has a long experience in probing exotic nuclei via quasi-free scattering reactions. To continue these studies a new array capable of detecting protons and gamma rays of high energy is currently being developed, the CALIFA (R3B CALorimeterfor In Flight γ arrays and high energy charged pArticles). This contribution reports on the current solution for the forward Endcap of the CALIFA detector and on the latest test results.

Radiotherapy-induced skin reactions: assessment and management

Radiotherapy, the use of high-energy rays to either kill cancer cells or treat some benign tumours, is undoubtedly a positive intervention. However, as the primary mode of action in radiotherapy treatment is the killing of cells to prevent replication, other non-cancerous cells may be affected. For example, up to 85% of patients will experience some form of skin reaction, which will range from local erythema to moist desquamation. Such reactions are not only distressing and painful for the patient, if severe enough, they may warrant a halt in treatment. This article outlines the aims and nature of radiotherapy, and then discusses the aetiology of skin reactions, risk factors for reaction, and assessment tools. Management interventions will also be shown, with emphasis on silicone dressings.

Innovative Design of Variable Visual Field Collimator Based on Conflict Resolution Theory of TRIZ

Collimators are used in radiosurgery or radiotherapy systems to accurately focus their high-energy rays on the target to avoid causing damage to the collateral healthy tissues. With the development of conformal radiotherapy techniques, variable visual field collimators (VVFC) are widely used and many designs of VVFC have been proposed. However, these designs still exhibit different deficiencies, e.g. unable to completely eliminate the radiation leakage due to the inter-block gaps. Therefore, in this paper, an innovative design of VVFC is proposed through analyzing the original VVFC, determining the conflicts and solving them using the inventive problem solving methods (TRIZ). Compared with the existing designs of VVFC, the proposed design enables the selection of suitable size of field for the treatment of different size of targets, and completely eliminates the radiation leakage due to inter-block gaps.

MiRNAs as Biomarkers for Brain Metastasis of Breast Cancer

Due to the rapid development of high-resolution imaging that allows clinicians to detect a primary tumor at an early stage, the survival of breast cancer patients has been significantly prolonged in the past decades. However, more than 90% of cancer deaths are still attributed to metastatic disease, and around 30% of patients with advanced stages of breast cancer develop brain metastasis [1,2]. Despite this clinical importance, the exact molecular mechanism of brain metastasis is as yet poorly understood, and we still lack a biomarker that helps in diagnosis and prognosis of this dreadful disease. Two subtypes of breast cancers have been shown to demonstrate a strong brain metastatic phenotype, HER2-positive and triple-negative (ER - PR - HER2 - ) tumors, and the median survival of these two subtypes are 3.7 and 9 months, respectively, compared with 15 months in the luminal subtype [3]. The consequences of brain metastasis are devastating, and the most common symptoms are constant headache, sensory disorder and seizures, which drastically impair the quality of life of both patients and their families. The primary approaches to treat patients with brain metastases include radiation therapy and surgery. However, due to the potentially serious side effects, technique feasibility needs to be taken into consideration before successful treatment. In the case of radiation therapy, stereotactic radiosurgery (SRS) and whole-brain radiotherapy (WBRT) are the most commonly used clinically, and in which high energy rays suppress tumor cell growth; however, these treatments may generate severe damage to the brain, such as physical trauma and cognitive malfunctions. Surgery is another option that only applies to patients with one or a few small lesions located in accessible regions. Chemotherapies have been widely used in treating both primary and metastatic tumors, and their effectiveness greatly depends on the stages

Results from KASCADE–Grande

The KASCADE–Grande experiment, located at Karlsruhe Institute of Technology (Germany) is a multi-component extensive air-shower experiment devoted to the study of cosmic rays and their interactions at primary energies 1014–1018eV. Main goals of the experiment are the measurement of the all-particle energy spectrum and mass composition in the 1016–1018eV range by sampling charged (Nch) and muon (Nμ) components of the air shower. The method to derive the energy spectrum and its uncertainties, as well as the implications of the obtained result, is discussed. An overview of the analyses performed by KASCADE–Grande to derive the mass composition of the measured high-energy comic rays is presented as well.

Bremsstrahlung dose of strontium-89 in therapy application

There has been an increased interest in strontium-89 (Sr-89) therapy, which emits relatively high-energy (1.495 MeV) beta rays. The production in vivo bremsstrahlung radiation sufficient for external imaging and this radiation hazard warrants evaluation. The bremsstrahlung (secondary radiation) of Sr-89 has been traditionally ignored in internal dosimetry calculation. We have estimated the bremsstrahlung dose of Sr-89 source in the muscle and bone to body the various body organs (such as adrenals, brain, breasts, gallbladder wall, LLI wall, small intestine, stomach, ULI wall, heart wall, kidneys, liver, lungs, muscle, ovaries, pancreas, red marrow, bone surfaces, skin, spleen, testes, thymus, thyroid, urine bladder wall, uterus, fetus, placenta, and total body) from distributed sources of Sr-89 in the muscle and bone. In the present study, muscle and bone is considered as source organs. The bremsstrahlung dose of Sr-89 source in a muscle is less than that of cortical bone. In both muscle and bone medium, bremsstrahlung dose decreases with distance. These estimated values show that the bremsstrahlung radiation absorbed dose contribution from an organ to itself is very small, but contribution to other organs is not always negligible especially when large amounts of Sr-89 may be involved as in therapy applications.

Luminescent Properties of Eu<sup>3+</sup>-Doped HfO<sub>2</sub> Powders Prepared by Combustion

Scintillators are ideal candidates used in detectors for X-ray ,γ-ray and high energy ray , and have been widely applied in nuclear medicine , high energy physics ,geologic survey , security inspection and material flaw detection. The high density of HfO2 is an attractive compound for host lattice activated by rare earth for applications as scintillating materials. This paper reported the synthesis of Eu3+ doped HfO2 nanopowders by chemical self-combustion method at low temperature. Analytical grade Eu(NO3)3 and high pure HfOCl2 were used as raw materials. The requisite amount of urea and glycine as the mixed fuel were added to the mixed solution. A little EDTA was used as a complexant. The mixed solution was dried at 200°C, and fired at 450°C. The powders synthesized by self-combustion were then calcined at 800°C to profit the crystal growth and improve the luminescent properties. XRD, TEM were employed to analyze the phase composition and the characteristics of as-obtained powders. The TEM images display typical nano-structured morphology of Eu3+ doped HfO2. Analysis of XRD indicates that Eu3+ doped HfO2 nanopowders are cubic phase. The excitation and emission spectra were analyzed by the fluorescence photometer. There are two peaks in emission spectra .One is at 595nm, and another is at 614nm. The luminescent properties also reveal the structure of cubic phase.

Irradiation stability and cytotoxicity of gold nanoparticles for radiotherapy

Gold nanoparticles are promising as a kind of novel radiosensitizer in radiotherapy. If gold nanoparticles are shown to have good irradiation stability and biocompatibility, they would play an important role in radiotherapy. In this work, we investigated irradiation effects of gold nanoparticles under 2-10 kR gamma irradiation and cytotoxicity of gold nanoparticles with human K562 cells by using Cell Titre-Glo luminescent cell viability assay. The results revealed that gamma irradiation had not induced any obvious instability and size variations in gold nanoparticles. We found that gold nanoparticles showed excellent radiation hardness with an absorbed dose conversation factor of 9.491 rad/R. Meanwhile, the surface plasmon resonance of gold nanoparticles was enhanced obviously after 2-10 kR gamma irradiation. Subsequently, cytotoxicity tests indicated that the extremely high concentration of gold nanoparticles could cause a sharp decrease in K562 cell viability, while the low concentration of gold nanoparticles had no obvious influence on the cell viability. Our results revealed that gold nanoparticles were stable under high-energy ray irradiation and showed concentration-dependent cytotoxicity.

The HERO project for the study of high-energy primary cosmic radiation

Proposals for the High-Energy Ray Observatory (HERO) comprising scientific equipment with increased power availability are presented. Under the long exposure (>7 years), it is proposed to investigate the spectrum and charge composition of cosmic-ray nuclei up to E0 ∼ 1016 eV and to determine the behavior of the energy spectrum in the energy regions >100 GeV for cosmic-ray electrons and >50 GeV for γ radiation. The geometrical factor of the apparatus is 6.0–9.0 m2 sr depending on the type of particles.

Radiation-chemical synthesis of tetrafluoroethylene telomers and their use for preparation of thin protective fluoropolymer coatings

The specific features and possibilities of preparation of protective coatings and composite materials based on fluoromonomers using high-energy rays (60Co γ-rays, fast electrons) were analyzed. The emphasis was placed on synthesis and application of tetrafluoroethylene telomers in acetone. The structure and properties of telomers were examined by IR and NMR spectroscopy, as well as by X-ray diffraction analysis and diathermy. The radiation initiation allows preparation of new products with a broad spectrum of functional properties and opens wider prospects for technological application of fluoromonomers.