Short Radiation Research Articles

Dose Rate Measurements in Pulsed Radiation Fields by Means of an Organic Scintillator

A deficiency in the implementation of current radiation protection is the determination of the ambient dose equivalent H*(10) and the directional dose equivalent H´(0.07) in pulsed radiation fields. Conventional dosimeter systems are not suitable for measurements in photon fields comprising short radiation pulses, which consequently leads to high detector loads in short time periods. Nevertheless, due to the implementation of advanced medical accelerators for cancer therapy, new medical diagnostic devices as well as various laser machining systems, there is an urgent need for suitable dosimeter systems for real time dosimetry. In this paper, a detector concept based on an organic scintillator and a full digital data analysis with the aim of developing a portable, battery powered measurement system is presented.

Short Radiative Lifetime and Non-Triplet Sensitization in Near-Infrared-Luminescent Yb(III) Complex with Tripodal Schiff Base.

We prepared Ln(III) (Ln=Eu, Gd, and Yb) complexes with a tripodal Schiff base, tris[2‐(5‐methylsalicylideneimino)ethyl]amine (H3L) and studied their photophysical properties. Upon ligand excitation, YbL showed Yb(III)‐centered luminescence in the near‐infrared region. While the overall quantum yield (0.60(1)%) of YbL in acetonitrile was moderate among the reported values for Yb(III) complexes, its radiative lifetime (0.33(2) ms) was significantly shorter than those reported previously. We propose that the ligand‐to‐metal charge‐transfer (LMCT) state mediated the sensitization in YbL. The emission and excitation spectra of EuL indicated the participation of the LMCT state in the sensitization. The radiative lifetime (0.84(7) ms) for EuL in the solid state was rather short compared to those of reported Eu(III) complexes. Our results show that the Yb(III) complex with the Schiff base ligand has two features: the short radiative lifetime and the non‐triplet sensitization path.

Laser-Assisted Sintering of Silver Nanoparticle Paste for Bonding of Silicon to DBC for High-Temperature Electronics Packaging

This article presents the development of a laser-assisted sintering method of a silver nanoparticle paste for bonding of a silicon chip to a direct bonded copper (DBC) substrate for high-temperature electronics packaging applications. The effects of the bonding parameters such as laser power, bonding pressure, and time on shear strength were studied. For comparison, samples using hotplate bonding were also produced and studied. Shear strength, cross section, and fracture surface analysis were carried out in reliability studies. The results show that shear strength of 10 MPa can be achieved at the bonding pressure of 3 MPa, laser power of 70 W, and a very short irradiation time of 1 min. The shear strength reached 20 MPa when the irradiation time was increased to 5 min. The research indicates that the shear strength can be improved by increasing the bonding pressure, laser power, and hence the sintering temperature and the irradiation time. The laser-assisted method with a short irradiation time of 5 min can produce the same level of shear strength as compared with the hotplate-based approach requiring a sintering time of tens of minutes. With the ability of fast and localized heating effect, the laser-assisted sintering method can improve the manufacturing efficiency for packaging of high-temperature electronics and sensors.

Clinical outcomes of transforaminal endoscopic lateral recess decompression by using the visualized drilled foraminoplasty and visualized reamed foraminoplasty: a comparison study

BackgroundLateral recess stenosis (LRS) is a common degenerative disease in the elderly. Since the rise of comorbidity is associated with increasing age, transforaminal endoscopic lateral recess decompression (TE-LRD) is advocated. The objective of this study was to compare the clinical outcomes of TE-LRD in patients with LRS via visualized drilled foraminoplasty (VDF) or visualized reamed foraminoplasty (VRF) technique.MethodsA total of 45 and 42 consecutive patients with limp or unilateral radiculopathy symptoms underwent TE-LRD using the VDF and VRF technique, respectively. The radiation exposure and operation time, time to return to work, and complications were compared between two groups. Their clinical outcomes were evaluated with the visual analogue scale (VAS) leg pain score, VAS back pain score, Oswestry Disability Index (ODI) and modified MacNab’s criteria.ResultsThe average values of radiation exposure and operative time in the VDF group were significantly higher than those in the VRF group (P < 0.05). The postoperative VAS and ODI scores in both groups were significantly improved compared with those before the operation (P < 0.05). In addition, the VAS score of the leg pain and ODI score in the VRF group were significantly lower than those in the VDF group at the 1-week follow-up (P < 0.05). The good-to-excellent rates of the VDF group and VRF group were 88.89 and 90.48%, respectively, whereas the complication occurrence rates were 6.67 and 4.76% in the VDF group and VRF group, respectively.ConclusionsTE-LRD performed by using VRF technique can be applied to treat LRS safely and effectively with short radiation exposure and operation time. This technique was comparable to the VDF technique with improved VAS leg pain and ODI scores in the short period after the operation. However, potential complications and risks still need to be considered.

Feasibility of dosimetric measurements using Al2O3:C OSL dosimeter during fluoroscopy-guided procedures

This study investigated the feasibility of dosimetric measurements using Al2O3:C optically stimulated luminescence (OSL) dosimeters during fluoroscopy-guided procedures. The linearity and energy dependence of Al2O3:C OSL dosimeters were evaluated, and the air kerma rate at the operator’s position was measured. The response of Al2O3:C OSL dosimeters to short, repetitive irradiations was compared to that of long uninterrupted irradiation. The change in response of the Al2O3:C OSL dosimeter under automatic exposure rate control (AERC) was evaluated with the use of various thicknesses of polymethyl-methacrylate (PMMA) plates (15–30 cm). The Al2O3:C OSL dosimeters could detect 5 µGy and showed good linearity in doses of ≥10 µGy (R2: 0.997–0.999, p < 0.001). The relative response of the Al2O3:C OSL dosimeter normalised to that of 36.8 keV was 0.828–1.101 at the energies investigated (30.6–46.0 keV). The air kerma rate at the operator’s position was estimated to be 2.61–7.17 µGy min−1 depending on the heights representing different body parts. Repetitive short irradiations had no significant impact on the relative response of the Al2O3:C OSL dosimeters (p > 0.05). Despite a high energy dependence on the low energy beam used in fluoroscopy, the change in relative response of the Al2O3:C OSL dosimeter under AERC was within 5.7% depending on the thickness of the PMMA plates. Dosimetric measurement using Al2O3:C OSL dosimeters for patients and operators is feasible. However, one should be cautious about high standard deviations when measuring small doses of ≤20 µGy using Al2O3:C OSL dosimeters. It is essential to perform intensive bleaching before measuring very small doses to minimise pre-irradiation counts.

The European Joint Research Project UHDpulse - Metrology for advanced radiotherapy using particle beams with ultra-high pulse dose rates.

UHDpulse - Metrology for advanced radiotherapy using particle beams with ultra-high pulse dose rates is a recently started European Joint Research Project with the aim to develop and improve dosimetry standards for FLASH radiotherapy, very high energy electron (VHEE) radiotherapy and laser-driven medical accelerators. This paper gives a short overview about the current state of developments of radiotherapy with FLASH electrons and protons, very high energy electrons as well as laser-driven particles and the related challenges in dosimetry due to the ultra-high dose rate during the short radiation pulses. We summarize the objectives and plans of the UHDpulse project and present the 16 participating partners.

The biology of corneal cross-linking derived from ultraviolet light and riboflavin

Over the past 20 years, corneal crosslinking (CXL) has been used by surgeons to halt progression in eyes with keratoconus. We reviewed the literature regarding the mechanism of action of CXL, the role of each of its components the strong biologic reaction, and their effects on cell interaction, proteins involved, wound healing, and cytotoxic reaction. CXL surgery involves a photochemical response in which ultraviolet light at a given wavelength and riboflavin participate. The combination of irradiation with UVA light and riboflavin leads to an intense process of apoptosis of keratocytes in the anterior stroma. Differences in light irradiation, as well as the importance of riboflavin and its vehicle, were also detailed. The surgery creates additional chemical bonds between the amino terminals of the collagen side chains and the proteoglycans of the extracellular matrix. A photosensitization reaction catalyzed by riboflavin classically involves the production of singlet oxygen. Microstructure studies show changes in the size of the fibril and potentially in the interfibrillar space, that the most significant changes related to the stiffening effect of CXL occur in the anterior third of the cornea and that short irradiation times, especially below 5 min, may not have the same biological effect. Changes in the riboflavin vehicle, with the incorporation of Hydroxypropyl methylcellulose as a carrier, can lead to faster diffusion and a more intense photochemical reaction. These are findings that can impact the optimal adjustment of irradiation time according to the riboflavin (and its carrier) used. Many studies have suggested that CXL is safe and effective in the standard and accelerated protocols that have been used by surgeons. After the initial depletion of anterior keratocytes, keratocyte density seems to return to average 6–12 months after surgery when corneas are examined with the confocal microscope.

Parallel-Stacked Flexible Organic Light-Emitting Diodes for Wearable Photodynamic Therapeutics and Color-Tunable Optoelectronics.

Deformable organic light-emitting diode (OLED) based optoelectronic devices hold promise for various wearable applications including biomedical systems and displays, but current OLED technologies require high voltage and lack the power needed for wearable photodynamic therapy (PDT) applications and wearable displays. This paper presents a parallel-stacked OLED (PAOLED) with high power, more than 100 mW/cm2, at low voltage (<8 V). The current dispersion ratio can be tuned by optimizing the structure of the individual OLEDs stacked to create the PAOLED, allowing control of the PAOLED's wavelength shapes, current efficiency, and power. In this study, a fabricated PAOLED operated reliably for 100 h at a high power of 35 mW/cm2. Confirming its potential application to PDT, the measured singlet oxygen generation ratio of the PAOLED was found to be 3.8 times higher than the reference OLED. The high-power PAOLED achieved a 24% reduction in melanoma cancer cell viability after a short (0.5 h) irradiation. In addition, a white light PAOLED with color tuning was realized through OLED color combination, and a high brightness of over 30 000 cd/m2 was realized, below 8.5 V. In conclusion, the PAOLED was demonstrated to be suitable for a variety of low-voltage, high-power wearable optoelectronic applications.

Rapidly Visible-Light-Mediated Photogelations for One-Step Engineering Multifunctional Tough Hydrogel Tubes.

Hydrogel tubes as one kind of perfusable tubular materials, show promising applications in a wide spectrum of fields. However, there is still a great challenge to design a rapid, biocompatible, and straightforward strategy for one-step engineering tough hydrogel tubes, which have excellent mechanical properties, unique resilience, and multiple functions. Herein, we explore visible-light-mediated orthogonal photochemistry to achieve the fabrication of tough hydrogel tubes with double networks via a coaxial-nozzle spinning technique under short blue-light irradiation (∼20 s). The as-prepared tubes are tough (2.3 MJ m-3) and have mechanical strength (∼300 kPa) with a critical strain of 16, good fatigue resistance, and resilience (>95% within 3 min). These perfusable tubular hydrogels not only can be knitted and assembled to complicated 2D/3D structures, but also are designed to fabricate functional tubes in one step with the applications in fields of smart materials, soft electronics, and sensors.

Dynamics and Emission of Relativistic Magnetic Dipoles of a Laser Cluster Plasma

It has been shown that the irradiation of a gas target with nanoclusters by a short (tens of femtoseconds), relativistically intense, circularly polarized laser pulse results in the appearance of magnetic dipoles, which are oriented in the direction of the propagation of the laser pulse and produce a quasi-static regular magnetic field with an amplitude to tenths of the field of the initial laser pulse. At a sufficient concentration of clusters, after the end of the laser pulse, the magnetic moments of the dipoles undergo vibrations and the magnetic field oscillates, which is accompanied by the appearance of a short (few-cycle) secondary terahertz radiation. The condition for the appearance of such a short terahertz pulse is that the cyclotron frequency of an electron on average over the volume of the magnetic field is higher than the inverse lifetime of the cluster.

Generation of an Attosecond Pulse Based on Collective Spontaneous Radiation Emission of a Layer of Three-Level Atoms Excited by a Pair of Unipolar Pulses

A method of coherent controlling the polarization of a medium has been proposed recently for the generation of extremely short pulses. The method is based on the excitation of atomic polarization oscillations and their subsequent stop using a pair of ultrashort pulses. The so-called stopped pulse of the polarization of a medium, which arises in the interval between its excitation and deexcitation, can be a source of an extremely short radiation pulse. In this work, the above-indicated possibility of generation of an isolated attosecond ultraviolet pulse in a three-level resonant medium whose parameters correspond to a hydrogen atom excited by a pair of unipolar X-ray pulses is considered theoretically. In this case, the generation mechanism is of the antenna-type, that is, it is caused by the collective spontaneous emission of pre-phased atoms in the absence of a noticeable decay of their free polarization.

Quantitative Assessment of Endosomal Escape of Various Endocytosed Polymer-Encapsulated Molecular Cargos upon Photothermal Heating.

Encapsulated molecular cargos are efficiently endocytosed by cells. For cytosolic delivery, understanding the dynamic process of cargos release from the carrier vehicles used for encapsulation and the lysosomes where the carrier vehicles are trapped (which in general is the bottleneck), followed by diffusion in the cytosol is important for improving drug/gene delivery strategies. A methodology is reported to image this process on a millisecond scale and to quantitatively analyze the data. Polyelectrolyte capsules with embedded gold nanostars to encapsulate 43 fluorescent molecular cargos with diverse properties, ranging from small fluorophores to fluorescently labeled proteins, siRNA, etc., are used. By short laser irradiation intracellular release of the molecular cargos from endocytosed capsules into the cytosol is triggered, and their intracellular spreading is imaged. Most of the released molecular cargos evenly distribute inside the entire cell, while others are enriched in certain cell compartments. The time the different molecular cargos take to distribute within cells, i.e., the spreading time, is used as a quantifier. Quantitative analysis reveals that intracellular spread cannot be described by free diffusion, but is determined by interaction of the molecular cargo with intracellular components.

Impact of Lymphopenia on Survival for Elderly Patients with Glioblastoma: A Secondary Analysis of the CCTG CE.6 (EORTC 26062-22061, TROG03.01) Randomized Clinical Trial

Lymphopenia (LMP) may lead to worse outcomes for patients with glioblastoma (GBM). This study is a secondary analysis of the CCTG CE.6 trial evaluating the impact of chemotherapy and radiation on LMP, as well as the association of LMP with overall survival. CCTG clinical trial CE.6 randomized elderly GBM patients (≥ 65 yrs) to short course radiation alone (RT) or short course radiation with temozolomide (RT + TMZ). In this study LMP (mild-mod: grade 1-2; severe: grade 3-4) was defined per CTCAE v3.0 criteria, and measured at baseline, 1 wk and 4 wks post-RT. Pre-selected key factors for the analysis included age, sex, ECOG, extent of resection, MGMT methylation, MMSE, and steroid use. Multinomial logistic regression models were used to identify factors associated with LMP and multivariable Cox regression models were used to study effect of LMP on survival. A total of 562 patients were included for analysis (281 RT vs 281 RT+TMZ). At baseline, both arms (RT vs RT+TMZ) had similar rates of mild-mod (21.4% vs 21.4%) and severe (3.2% vs 2.9%) LMP. The 1 wk post-RT LMP rates were also similar (p = 0.25). However, RT+TMZ pts were more likely to develop both mild-mod LMP (18.2% vs 27.9%) and severe LMP (1.8% vs 9.3%) [p < 0.001] at 4 wks post-RT. Developing mild-mod and severe LMP post-RT were both associated with baseline LMP (p < 0.001) and RT+TMZ (p < 0.001). Severe LMP at 4 wks post-RT was also associated with biopsy only (p < 0.02). After adjusting for confounding factors, 4 wks post-RT LMP was not significantly associated with PFS or OS regardless of severity. However, baseline LMP (HR 1.3) was significantly associated with worse OS (HR: 1.30, 95% C.I.: 1.05-1.62, p = 0.02), regardless of MGMT status. Other factors significantly associated with worse outcome included: males (HR 1.41), biopsy only (HR 1.59), and lower MMSE (HR 1.03). Short course RT alone does not lead to LMP after treatment. Development of LMP post-RT is associated with addition of TMZ and baseline LMP. However, only baseline LMP is associated with worse OS regardless of MGMT status. This may be considered as a prognostic biomarker for elderly GBM patients and warrants further validation.

Photothermal Effect of Superparamagnetic Fe3O4 Nanoparticles Irradiated by Near-Infrared Laser

Fe3O4 nanoparticles (NPs) have been widely used in biomedicine due to their unique magnetism, biocompatibility, and biodegradability. Magnetic hyperthermia of Fe3O4 NPs for cancer treatment has attracted more attention. However, it could interfere with magnetic field-sensitive devices of patients, such as pacemakers. Therefore, it is necessary to find a new method for clinical therapy. In this study, the superparamagnetic Fe3O4 NPs were fabricated. Visible-near-infrared absorption spectra indicated that the Fe3O4 NPs have near-infrared absorption. The influences of Fe3O4 NP concentrations, power density, and wavelength of near-infrared laser irradiation on the photothermal performance of Fe3O4 NPs were investigated. The results revealed that high concentrations, large power density, and short irradiation wavelength could improve the photothermal performance of Fe3O4 NPs. The temperature variation and the absorption intensity simultaneously determined the photothermal transduction efficiency of Fe3O4 NPs. The application of the photothermal performance of Fe3O4 NPs would provide a new opportunity for clinic cancer treatment.

The use of ultrasound and ozone therapy in the complex treatment of periodontitis

Physiotherapy makes it possible to effectively influence all the links in the pathogenesis of periodontitis. The use of ultrasound plays a special role in the treatment of periodontal diseases. With the help of ultrasonic vibrations, drugs (ultraphonophoresis) can be introduced into the tissue. For its implementation, water and oil solutions of medicinal substances are used. In periodontal practice, ultrasound is most often used to remove dental plaque. It is of scientific interest to use low-frequency ultrasound in combination or in combination with physical factors that have a pronounced antibacterial effect, such as ozone . High oxidizing properties of ozone provide its therapeutic effect, manifested in disinfecting, metabolic, immunomodulating and deodorizing effects. When conducting local ozone therapy in the oral cavity, it is necessary to accurately dose the concentration of ozone, therefore, in our opinion, the use of ozonized solutions and oils in dentists is safer and more promising. The combined and combined effects in the treatment of periodontitis of low-frequency ultrasound and ozone therapy, in the production of ozone using short ultraviolet radiation, will provide a comprehensive therapeutic effect, which consists in suppressing the vital activity of pathogenic microorganisms and stimulating metabolic processes in the tissues of the macroorganism.

Functionalized graphene oxide nanosheets with unique three-in-one properties for efficient and tunable antibacterial applications

Developing antibiotics-independent antibacterial agents is of great importance since antibiotic therapy faces great challenges from drug resistance. Graphene oxide (GO) is a promising agent due to its natural antibacterial mechanisms, such as sharp edge-mediated cutting effect. However, the antibacterial activity of GO is limited by its negative charge and low photothermal effect. Herein, the amino-functionalized GO nanosheets (AGO) with unique three-in-one properties were synthesized. Three essential properties (positive charge, strong photothermal effect, and natural cutting effect) were integrated into AGO. The positive charge (30 mV) rendered AGO a strong interaction force with model pathogen Streptococcus mutans (330 nN). The natural cutting effect of 100 µg·mL−1 AGO caused 27% loss of bacterial viability after incubation for 30 min. Most importantly, upon the near-infrared irradiation for just 5 min, the three-in-one properties of AGO caused 98% viability loss. In conclusion, the short irradiation period and the tunable antibacterial activity confer the three-in-one AGO a great potential for clinical use.

Nickel ferrite nanoenabled graphene oxide (NiFe2O4@GO) as photoactive nanocomposites for water treatment.

Nanocomposite materials can enhance the capabilities of water treatment processes such as photocatalysis. In this work, novel light-driven nanocatalysts were synthesized by using nickel ferrite (NiFe2O4) to nanoenable graphene oxide (GO) substrates. GO is an emerging 2D nanomaterial with high conductivity and adsorption properties. Moreover, the electric properties of GO improve photocatalytic performance by promoting charge carrier separation. Results of the characterization of the nickel ferrite nanoenabled graphene oxide (NiFe2O4@GO) nanocomposites demonstrate that homogeneous and stable photocatalysts were produced. The as-synthesized nanocatalysts enabled complete decolorization of the colored water matrix in short irradiation times of 150 min using minimal catalyst loading at 0.5 g L-1. The selective hook and destroy mechanism reduced the competitive effect of co-existing ions in solution. Furthermore, the use of specific scavengers helped to elucidate the degradation mechanisms of organic dye methylene blue by NiFe2O4@GO nanocomposites.

The prolonged gamma ray enhancement and the short radiation burst events observed in thunderstorms at Tien Shan

We report the observation results of the hard radiation flashes which accompanied the lightning discharges above the mountains of Northern Tien Shan. Time series of the counting rate intensity, numerical estimations of absolute flux, and energy distribution of accelerated electrons and of (20−2000) keV gamma rays were obtained at the height of 3700 m a. s. l., immediately within thunderclouds, and in closest vicinity (≲100 m) to discharge region. Two different kinds of radiation emission events are presented here: a relatively prolonged rise of gamma ray intensity with minute-scale duration (the thunderstorm ground enhancement, TGE) which has preceded a negative field variation, and a short sub-millisecond radiation burst, which accompanied a close lightning discharge in thundercloud. It was revealed also an indication to positron generation in thunderclouds at the time of gamma ray emission, as well as modulation of the neutron counting rate in Tien Shan neutron monitor which was operating at a (1.5–2) km order distance from the region of lightning development.

Dry pasteurization of paprika (Capsicum annuum L.) by short time intensive microwave-infrared radiation: Inactivation of Salmonella Typhimurium and Aspergillus flavus considering quality degradation kinetics

The inactivation of S. Typhimurium and A. flavus along with quality degradation kinetics was studied during combined microwave-infrared (MW-IR) heating of paprika. The spatial changes in the distribution of temperature and variation in water activity (aw) of the paprika samples resulted in a 7.389 log reduction in S. Typhimurium, and 6.182 log reduction in A. flavus. During heating, the deterioration of red pigments was more pronounced compared to that of the yellow pigments. The alteration of color was observed to be due to the increase in a large number of brown pigments. The inhibition of DPPH radicals accelerated with an increase in the power level of MW-IR radiation; the inhibition rate increased from 0.0859 to 0.1485 s−1. Also, the pungency of dried paprika was found to increase due to moisture reduction, inactivation of peroxidase, and the short-duration of heating.

Impact of radiotherapy on circulating lymphocyte subsets in patients with esophageal cancer.

Radiotherapy (RT) can affect the immune function of patients with cancer. The purpose of this study was to investigate the effect of RT on lymphocyte and its subsets in patients with esophageal cancer (EC).All patients received RT with a mean dose of 5369 cGy (gray). Blood parameters were measured in 31 patients on 3 occasions (before, at the end of radiotherapy, and at 3 months follow-up). The whole blood count and lymphocyte subsets were measured and correlated with short time efficiency and radiation dose parameters.White blood count (WBC) and lymphocyte count (ALC) were greatly decreased at the end of radiotherapy, and the percentages of CD3+, CD3+CD8+ T cells were significantly increased, on the other hand, a decrease in the CD4/CD8 ratio was observed. The percentages of CD3-CD16/56+NK cells and CD19+ B cell were decreased at the end of RT compared with prior RT. The percentages of CD3+ T cells before RT and the WBC and ALC count after RT can be used as prognostic indicators for survival. The PTV dose can cause significant changes in lymphocytes count after RT. CD3+T cells after RT were significantly correlated with mean heart dose and heart V50.Our study identified that RT causes changes in lymphocyte subsets, and these changes may indicate differences in immune function between individuals. Radiotherapy plan should be designed to minimize normal tissue dose to reduce the impact on WBC and lymphocytes.