High-energy X-ray Beams Research Articles

Energy Absorption and Beam Damage during Microfocus Synchrotron X-ray Diffraction.

In this study, we combine in situ fast differential scanning calorimetry (FDSC) with synchrotron X-ray measurements to study simultaneously the structure and thermophysical properties of materials. Using the example of the organic compound BCH-52, we show that the X-ray beam can heat the sample and induce a shift of the heat-flow signal. The aim of this paper is to investigate the influence of radiation on sample behavior. The calorimetric data is used to quantify the absorbed beam energy and, together with the diffraction data, reveal an irreversible damage of the sample. The results are especially important for materials with high absorption coefficients and for high-energy X-ray and electron beams. Our findings illustrate that FDSC combined with X-ray diffraction is a suitable characterization method when beam damage must be minimized.

UMobileNetV2 model for semantic segmentation of gastrointestinal tract in MRI scans.

Gastrointestinal (GI) cancer is leading general tumour in the Gastrointestinal tract, which is fourth significant reason of tumour death in men and women. The common cure for GI cancer is radiation treatment, which contains directing a high-energy X-ray beam onto the tumor while avoiding healthy organs. To provide high dosages of X-rays, a system needs for accurately segmenting the GI tract organs. The study presents a UMobileNetV2 model for semantic segmentation of small and large intestine and stomach in MRI images of the GI tract. The model uses MobileNetV2 as an encoder in the contraction path and UNet layers as a decoder in the expansion path. The UW-Madison database, which contains MRI scans from 85 patients and 38,496 images, is used for evaluation. This automated technology has the capability to enhance the pace of cancer therapy by aiding the radio oncologist in the process of segmenting the organs of the GI tract. The UMobileNetV2 model is compared to three transfer learning models: Xception, ResNet 101, and NASNet mobile, which are used as encoders in UNet architecture. The model is analyzed using three distinct optimizers, i.e., Adam, RMS, and SGD. The UMobileNetV2 model with the combination of Adam optimizer outperforms all other transfer learning models. It obtains a dice coefficient of 0.8984, an IoU of 0.8697, and a validation loss of 0.1310, proving its ability to reliably segment the stomach and intestines in MRI images of gastrointestinal cancer patients.

Treatment Planning System in Radiotherapy: A Short Review

Treatment planning is the core in radiotherapy. The present study aimed to explore the relationship between treatment planning system and radiotherapy. Some of the important steps in radiation treatment planning system have been discussed in this paper such as patient positioning, contouring, and simulation of pre-treatment. Detailed information has been acquired by the author associated with dose calculations in different conditions,techniques used in beam modification. Since ionising radiation creates ions in the cells of the tissues where it travels through, hence it has the capability to treat cancercells. By taking away electrons from atoms and molecules, ions are created. It can therefore either eliminate the genes or inhibit their growth. The molecular processes leading to tissue damage illustrate that ionizing radiation not only globally affects biomolecules but also selectively alters various biomolecules in response to chemotherapy. Linear accelerator is abbreviated as LINAC. It produces high energy electron or X-ray beams using electricity. Although there are many applications for thesebeams, cancer treatment is one of them.

Time-Resolved Radioluminescence Dosimetry Applications and the Influence of Ge Dopants In Silica Optical Fiber Scintillators

The quality of treatment delivery as prescribed in radiotherapy is exceptionally important. One element that helps provide quality assurance is the ability to carry out time-resolved radiotherapy dose measurements. Reports on doped silica optical fibers scintillators using radioluminescence (RL) based radiotherapy dosimetry have indicated merits, especially regarding robustness, versatility, wide dynamic range, and high spatial resolution. Topping the list is the ability to provide time-resolved measurements, alluding to pulse-by-pulse dosimetry. For effective time-resolved dose measurements, high temporal resolution is enabled by high-speed electronics and scintillator material offering sufficiently fast rise and decay time. In the present work, we examine the influence of Ge doping on the RL response of Ge-doped silica optical fiber scintillators. We particularly look at the size of the Ge-doped core relative to the fiber diameter, and its associated effects as it is adjusted from single-mode fiber geometry to a large core-to-cladding ratio structure. The primary objective is to produce a structure that facilitates short decay times with a sufficiently large yield for time-resolved dosimetry. RL characterization was carried out using a high-energy clinical X-ray beam (6 MV), delivered by an Elekta Synergy linear accelerator located at the Advanced Medical and Dental Institute, Universiti Sains Malaysia (USM). The Ge-doped silica optical fiber scintillator samples, fabricated using chemical vapor deposition methods, comprised of large core and small core optical fiber scintillators with high and low core-to-cladding ratios, respectively. Accordingly, these samples having different Ge-dopant contents offer distinct numbers of defects in the amorphous silica network. Responses were recorded for six dose-rates (between 35 MU/min and 590 MU/min), using a photomultiplier tube setup with the photon-counting circuit capable of gating time as small as 1 μs. The samples showed linear RL response, with differing memory and afterglow effects depending on its geometry. Samples with a large core-to-cladding ratio showed a relatively short decay time (<1 ms). The results suggest a contribution of Ge-doping in affecting the triplet states of the SiO2 matrix, thereby reducing phosphorescence effects. This is a desirable feature of scintillating glass materials that enables avoiding the pulse pile-up effect, especially in high dose-rate applications. These results demonstrate the potential of Ge-doped optical-fiber scintillators, with a large core-to-cladding ratio for use in time-resolved radiation dosimetry.

The NMIJ air kerma primary standard for high energy x-ray beams in 300–450 kV

Accurate radiation dosimetry is required for radiation protection in various environments. Therefore, dosemeters and dose-rate meters must be calibrated in standard radiation fields. The National Metrology Institute of Japan (NMIJ) expands the energy range of x-ray reference field measurement up to 450 kV using a cylindrical graphite-walled cavity ionization chamber. Departure from the condition of the Spencer-Attix cavity theory was evaluated by comparing the measurement results obtained using the cavity ionization and the free-air ionization chambers, which are used as the primary standard up to a tube voltage of 250 kV. The calibration coefficients found using the spherical ionization chamber were in good agreement with those obtained by the free-air ionization chamber within relative standard uncertainties (k = 1) for N-200 and N-250 x-ray fields. Consistent calibration coefficients were obtained in the energy range 300–450 kV.

Feasibility study of a chlorophyll dosimeter for high energy X-ray beam used in radiotherapy

Feasibility study of a chlorophyll dosimeter for high energy X-ray beam used in radiotherapy

Variation of 4 MV X-ray dose rate in fractionated irradiation strongly impacts biological endothelial cell response in vitro

Purpose Even though X-ray beams are widely used in medical diagnosis or radiotherapy, the comparisons of their dose rates are scarce. We have recently demonstrated in vitro (clonogenic assay, cell viability, cell cycle, senescence) and in vivo (weight follow-up of animals and bordering epithelium staining of lesion), that for a single dose of irradiation, the relative biological effectiveness (RBE) deviates from 1 (up to twofold greater severe damage at the highest dose rate depending on the assay) when increasing the dose rate of high energy X-ray beams. Material and methods To further investigate the impact of the dose rate on RBE, in this study, we performed in vitro fractionated irradiations by using the same two dose rates (0.63 and 2.5 Gy.min−1) of high-energy X-rays (both at 4 MV) on normal endothelial cells (HUVECs). We investigated the viability/mortality, characterized radiation-induced senescence by using flow cytometry and measured gene analysis deregulations on custom arrays. Results The overall results enlighten that, in fractionated irradiations when varying the dose rate of high-energy X-rays, the RBE of photons deviates from 1 (up to 2.86 for viability/mortality experiments performed 21 days postirradiation). Conclusion These results strengthen the interest of multiparametric analysis approaches in providing an accurate evaluation of the outcomes of irradiated cells in support of clonogenic assays, especially when such assays are not feasible.

On single-crystal total scattering data reduction and correction protocols for analysis in direct space

Data reduction and correction steps and processed data reproducibility in the emerging single-crystal total-scattering-based technique of three-dimensional differential atomic pair distribution function (3D-ΔPDF) analysis are explored. All steps from sample measurement to data processing are outlined using a crystal of CuIr2S4 as an example, studied in a setup equipped with a high-energy X-ray beam and a flat-panel area detector. Computational overhead as pertains to data sampling and the associated data-processing steps is also discussed. Various aspects of the final 3D-ΔPDF reproducibility are explicitly tested by varying the data-processing order and included steps, and by carrying out a crystal-to-crystal data comparison. Situations in which the 3D-ΔPDF is robust are identified, and caution against a few particular cases which can lead to inconsistent 3D-ΔPDFs is noted. Although not all the approaches applied herein will be valid across all systems, and a more in-depth analysis of some of the effects of the data-processing steps may still needed, the methods collected herein represent the start of a more systematic discussion about data processing and corrections in this field.

A portable NIR fluorimeter directly quantifies singlet oxygen generated by nanostructures for Photodynamic Therapy

This paper reports on the setting up and calibration of a portable NIR fluorimeter specifically developed for quantitative direct detection of the highly reactive singlet oxygen (1O2) chemical specie, of great importance in Photodynamic therapies. This quantification relies on the measurement of fluorescence emission of 1O2, which is peaked in the near-infrared (NIR) at λ=1270nm.In recent years, several nanostructures capable of generating reactive oxygen species (ROS) when activated by penetrating radiation (X-rays, NIR light) have been developed to apply Photodynamic Therapy (PDT) to tumours in deep tissue, where visible light cannot penetrate. A bottleneck in the characterization of these nanostructures is the lack of a fast and reliable technique to quantitatively assess their performances in generating ROS, and in particular 1O2. For instance, the widely used PDT “Singlet Oxygen Sensor Green” kit suffers from self-activation under X-ray irradiation.To solve this difficulty, we propose here direct detection of 1O2 by spectroscopic means, using an apparatus developed by us around a recent thermoelectrically-cooled InGaAs single photon avalanche photodiode (SPAD). The SPAD is coupled to a custom-made integrating sphere designed for use under irradiation with high-energy X-ray beams from clinical Radiotherapy sources. We determine the detection threshold for our apparatus, which turns to be ∼9·1081O2 in realistic experimental condition and for measurements extending to 1 min of integration. After calibrations on standard photosensitizers, we demonstrate the potentiality of this instrument characterizing some photosensitizing nanostructures developed by us.

Ge-doped silica optical fibre for Time Resolved Radiation Dosimetry

Time-resolved radiation dosimetry in radiotherapy helps determine the quality of delivery of patient prescribed doses. Earlier reports on doped silica optical fibres as scintillators in radioluminescence (RL) based radiation dosimetry have indicated particular merits, including versatility, robustness, high spatial resolution, wide dynamic range, and the ability for real-time measurements. Time-resolved radiation dosimetry requires high temporal resolution, enabled using a suitable scintillator and high-speed electronics. We report on the potential of Ge-doped optical fibres as a suitable scintillator to be adopted for use in a time-resolved radiation dosimetry system. High-energy clinical X-ray beams (6 MV) were used to irradiate the Ge-doped optical fibre samples. RL responses were recorded for six dose-rates (between 100 MU/min and 600 MU/min) delivered by a Varian 2100 C/D linear accelerator. The photon-counting circuit gating time was set at its shortest capability of 100 μs? The Ge-doped optical-fibre scintillator showed linear RL response, with minimal observable memory and afterglow and plateau effects. The fluorescence lifetime analysis, demonstrate a calculated rise time of 590.1 ns and a decay time of 0.423 μs, indicating superior performance compared to other scintillator forms. These results demonstrate the potential for the Ge-doped optical-fibre scintillator to be used in a time-resolved radiation dosimetry system.

Probing Multiconfigurational States by Spectroscopy: The Cerium XAS L3 -edge Puzzle.

Invited for the cover of this issue are Prof. Jochen Autschbach and Dr. Dumitru-Claudiu Sergentu of State University of New York at Buffalo, and Dr. Corwin H. Booth of Lawrence Berkeley National Laboratory. The image depicts high-energy X-ray beams as lightnings probing Ce at the L3 edge in the iconic covalent-bonded Ce(C8 H8 )2 and in CeO2 . The mountain peaks in the background represent the double-peaked L3 edges. The peaks turn out to be intuitively interpreted in terms of localized orbitals and hence metal oxidation states. Read the full text of the article at 10.1002/chem.202100145.

Sedation and anesthesia of pediatric patient for External beam radiotherapy (XRT)

BACKGROUND: External beam radiation delivers a beam of high-energy x-rays to a patient's tumor site, Ιn order to destroy the cancer cells. External beam radiation gets its name from the fact that the beams come from an external source (a machine called a linear accelerator) and are aimed at the site of the tumor.AIM: was to obtain the most recent guideline in sedation and anesthesia of pediatric patient for External beam radiotherapy (XRT). Providing sedation anesthesia techniques during the performance of diagnostic and therapeutic procedures οn children decreases anxiety, discomfort, and pain and may improve child wellbeing. Immobilization is a pre-requisite for accurate radiotherapy. SUBJECTS and METHODS: This is a review article, the search was performed in MEDLINE , Embase , Pubmed, and CINHAL. RESULTS: Anesthetic drugs can be used in sub-anesthetic doses to cause sedation but, because they are potent, the difference between sedative and anesthetic doses is too small and airway skills are required too often for non-anesthetists to use them.C0NCLUSION: Sedation and anesthesia of pediatric patients have serious associated risks, as hypoventilation, apnea airway obstruction and cardiopulmonary impairment or depression. These risks should be avoided, diagnosed rapidly and treated appropriately. Medical practitioners responsible for the sedation process should know the nature of the sedatives and their side-effects. They should be able to detect and manage complications.This study was approved by the institutional ethical committee.

Two-dimensional Wide-Angle X-ray Scattering on a Cm-doped borosilicate glass in a beryllium container.

The two-dimensional wide-angle X-ray diffraction technique was applied to a Cm-doped borosilicate glass in a beryllium container. The experiment involved a high-energy X-ray beam and an image plate. It is shown that it is possible to extract the structure factor of the radioactive glass successfully from diffraction patterns and compare it with that of the pristine one. Striking differences appear under the first diffraction peak, revealing new sub-structures for the radioactive glass. It is suggested that they could be related to structural changes in the medium-range order, in particular the size distribution of rings or chains under the influence of mixed interactions between the glass network, α-particles and recoil nuclei.

Operating a graphite calorimeter in quasi-isothermal mode under high-energy x-ray beams

In this study, we developed a semi-active method to run a graphite calorimeter in the quasi-isothermal mode under high-energy x-ray beams. The rate of energy imparted by the beam during irradiation was compensated mainly by removing the electrical heating power based on the pre-calculation and in part by an active automated algorithm, as well, while the temperature of the calorimeter core was kept constant. Irradiations were performed under the linear electron accelerator x-ray beams at 6, 8, 10, 15, and 18 MV. A simple model was applied to analyze the results. The energy imparted to the core was determined with an uncertainty level of 0.2%–0.3%, and the results were reaffirmed by comparing it with that obtained by the quasi-adiabatic mode. The normalized root-mean-square deviation to the mean from the quasi-adiabatic mode was 0.11%, and the associated uncertainty was 0.16% taking into account the correlation of the uncertainty components. This level of agreement showed that the present method is practical for the high-energy x-ray dosimetry.

Ion-Mediated Cross-linking of Biopolymers Confined at Liquid/Liquid Interfaces Probed by In Situ High-Energy Grazing Incidence X-ray Photon Correlation Spectroscopy.

As manifested in biological cell membranes, the confinement of chemical reactions at the 2D interfaces significantly improves the reaction efficacy. The interface between two liquid phases is used in various key processes in industries, such as in food emulsification and floatation. However, monitoring the changes in the mechanics and dynamics of molecules confined at the liquid/liquid interfaces still remains a scientific challenge because it is nontrivial to access the interface buried under a liquid phase. Herein, we report the in situ monitoring of the cross-linking of polyalginate mediated by Ca2+ ions at the oil/water interface by grazing incidence X-ray photon correlation spectroscopy (GIXPCS). We first optimized the reaction conditions with the aid of interfacial shear rheology and then performed GIXPCS using a high-energy synchrotron X-ray beam (22 keV) that guarantees sufficiently high transmittance through the oil phase. The intensity autocorrelation functions implied that the formation of a percolated network of polyalginate is accompanied by increasing relaxation time. Moreover, the relaxation rate scales linearly with the momentum transfer parallel to the interface, suggesting that the process is driven by hyperdiffusive propagation but not by Brownian diffusion. Our data indicated that high-energy GIXPCS has potential for in situ monitoring of changes in the dynamics of polymers confined between two liquid phases.

Influence of a shape of gold nanoparticles on the dose enhancement in the wide range of gold mass concentration for high-energy X-ray beams from a medical linac.

This work is focused on the Monte Carlo microdosimetric calculations taking into account the influence of the AuNPs' shape, size and mass concentration on the radiation dose enhancement for the high-energy 6 MV and 18 MV X-ray therapeutic beams from a medical linac. Due to a high atomic number and the photoelectric effect, gold nanoparticles can significantly enhance doses of ionizing radiation. However, this enhancement depends upon several parameters, such as, inter alia, nanoparticles' shape etc. The simulated system was composed of the therapeutic beam, a water phantom with the target volume (with and without AuNPs) located at the depth of the maximum dose, i.e. at 1.5 cm for the 6 MV beam and at 3.5 cm for the 18 MV one. In the study the GEANT4 code was used because it makes it possible to get a very short step of simulation which is required in case of simulating the radiation interactions with nanostructures. The dependence between the dose increase and the mass concentration of gold was determined and described by a simple mathematical formula for three different shapes of gold nanoparticles - two nanorods of different sizes and a flat 2D structure. The dose increase with the saturation occurring with the increasing mass concentration of gold was observed. It was found that relatively large cylindrical gold nanoparticles can limit the increase of the dose absorbed in the target volume much more than the large 2D gold nanostructure.

Prediction of radiation-induced malfunction for cardiac implantable electronic devices (CIEDs).

Cardiac implantable electronic devices (CIEDs) were believed to possess a tolerance dose to malfunction during radiotherapy. Although recent studies have qualitatively suggested neutrons as a cause of malfunction, numerical understanding has not been reached. The purpose of this work is to quantitatively clarify the contribution of secondary neutrons from out-of-field irradiation to the malfunction of CIEDs as well as to deduce the frequency of malfunctions until completion of prostate cancer treatment as a typical case. Measured data were gathered from the literature and were re-analyzed. Firstly, linear relationship for a number of malfunctions to the neutron dose was suggested by theoretical consideration. Secondly, the accumulated number of malfunctions of CIEDs gathered from the literature was compared with the prescribed dose, scattered photon dose, and secondary neutron dose for analysis of their correlation. Thirdly, the number of malfunctions during a course of prostate treatment with high-energy X-ray, passive proton, and passive carbon-ion beams was calculated while assuming the same response to malfunctions, where X-rays consisted of 6-MV, 10-MV, 15-MV, and 18-MV beams. Monte Carlo simulation assuming simple geometry was performed for the distribution of neutron dose from X-ray beams, where normalization factors were applied to the distribution so as to reproduce the empirical values. Linearity between risk and neutron dose was clearly found from the measured data, as suggested by theoretical consideration. The predicted number of malfunctions until treatment completion was 0, 0.02±0.01, 0.30±0.08, 0.65±0.17, 0.88±0.50, and 0.14±0.04 when 6-MV, 10-MV, 15-MV, 18-MV, passive proton, and passive carbon-ion beams, respectively, were employed, where the single model response to a malfunction of 8.6±2.1Sv- 1 was applied. Numerical understanding of the malfunction of CIEDs has been attained for the first time. It has been clarified that neutron dose is a good scale for the risk of CIEDs in radiotherapy. Prediction of the frequency of malfunction as well as discussion of the risk to CIEDs in radiotherapy among the multiple modalities have become possible. Because the present study quantitatively clarifies the neutron contribution to malfunction, revision of clinical guidelines is suggested.

Monte Carlo studies on dose conversion factors from graphite to water for high energy X-ray beams

An evaluation of the dose conversion factor from graphite to water is essential to measure the absorbed dose to water using a graphite calorimeter. However, it is difficult to obtain the conversion factors from measurements. In the present study, Monte Carlo (MC) studies were performed to evaluate the absorbed dose conversion factor from graphite to water. Based on the Electron Gamma Shower MC codes from National Research Council Canada, the modeling of the medical linear accelerator gantry at the Korea Research Institute of Standards and Science (KRISS) was optimized to obtain phase space files for evaluation of the absorbed dose conversion factor from graphite to water. The evaluated dose conversion factors for the KRISS graphite calorimeter were in the range of 1.040–1.085 for beams of 6–25 MV. A linear correlation between the dose conversion factors and tissue phantom ratio in water at depths of 20 cm and 10 cm (TPR20,10) of each X-ray beam was observed. To understand sensitivity of the obtained dose conversion factors, case studies were performed under different conditions in the simulation, such as different electron stopping power, assumed graphite bulk density, and different MC code. The uncertainties of the dose conversion factors will be finalized considering the results of sensitivity studies in the present study and additional studies in the future.

The nondestructive measurement of strain distributions in air plasma sprayed thermal barrier coatings as a function of depth from entire Debye-Scherrer rings.

The residual strain distribution has been measured as a function of depth in both top coat and bond coat in as-received and heat-treated air plasma sprayed thermal barrier coating samples. High-energy synchrotron X-ray beams were used in transmission to produce full Debye-Scherrer rings whose non-circular aspect ratio gave the in-plane and out-of-plane strains far more efficiently than the sin2ψ method. The residual strain in the bond coat is found to be tensile and the strain in the β phase of the as-received sample was measured. The residual strains observed in the top coat were generally compressive (increasing towards the interface), with two kinds of nonlinear trend. These was a 'jump' feature near the interface, and in some cases there was another 'jump' feature near the surface. It is shown how these trend differences can be correlated to cracks in the coating.

Bilateral comparison of the absorbed dose to water in high energy X-ray beams between the KRISS and the NMIJ

The Korea Research Institute of Standards and Science (KRISS) established a new standard of the absorbed dose to water in LINAC X-ray beams. To confirm the equivalence of the new standard with other national metrology institutes (NMIs), a bilateral comparison study of the absorbed dose to water in high energy X-ray beams was performed between the KRISS and the National Metrology Institute of Japan (NMIJ). The comparison was made in-directly. Three transfer chambers were calibrated in the high energy X-ray beams by both laboratories and the calibration coefficients were compared. The average ratios of the calibration coefficients of the three transfer chambers obtained by the KRISS to those obtained by the NMIJ were 1.004, 1.006, 1.006, 1.007 for 6, 10, 15 and 18 MV X-ray beams, respectively. The calibration coefficients obtained at the KRISS were higher than those at the NMIJ but they were in good agreement within the expanded uncertainty of 1.0% (k = 2). The results of this study will be used as the evidence for the KRISS standard being comparable with those of other NMIs, temporarily, in the interim period up to finalizing a key comparison study, BIPM.RI(I)–K6 managed by the Consultative Committee for Ionizing Radiation.