Dosimetry and Quality Control in Electron Beam Processing

2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document on Optimal Use of Ionizing Radiation in Cardiovascular Imaging: Best Practices for Safety and Effectiveness.

A vibration-acoustic method for diagnostics and monitoring of production processes such as cutting metals makes it possible compared with other methods to reduce the requirement for measuring equipment and it provides a computer representation of the results observed. The set of equipment suggested has low cost and it exhibits considerable flexibility compared with existing equipment.

<p indent="0mm">Ultra-high dose rate radiotherapy (FLASH-RT) has emerged as a hot topic in the field of radiotherapy in recent years. A series of experimental data indicate that FLASH-RT can effectively kill tumors while significantly spare normal tissues from radiation damage. This unique phenomenon is known as the FLASH effect. Whether the FLASH effect is triggered or not is influenced by various factors, including physical parameters and biochemical parameters. Physical parameters include dose rate, total dose, dose fractionation strategy, and beam structure, whereas biochemical parameters include tissue oxygenation level, tissue type, and biological endpoint. Adjusting these parameters can have differing degrees of impact on tissue responses to FLASH-RT. For instance, experimental data indicate that, compared to conventional radiation therapy (CONV-RT), FLASH-RT with an average dose rate exceeding <sc>100 Gy/s</sc> can completely protect mice’s cognitive function. However, this protective effect diminishes as the dose rate decreases and disappears when the dose rate falls below <sc>30 Gy/s.</sc> A review of published data suggests that the degree of reduction in normal tissue toxicity by FLASH-RT is influenced by the dose in a single fraction. Higher single doses result in greater reductions in toxicity, but excessively high doses can trigger severe late-stage adverse effects, which warrant caution. For beam structure and radiation type, the types of radiation currently used in preclinical FLASH-RT research include low-energy electrons, very high energy electrons (VHEE), low-energy X-rays, high-energy X-rays, protons, and heavy ions. Overall, the biological effects of FLASH-RT produced by different types of radiation are similar and consistent. However, the technical routes used to generate FLASH-RT beams reported in the literature vary widely, and the beam structures used in different studies differ significantly. It is necessary to clearly describe the detailed beam structure information used in experiments, including dose, dose rate, irradiation time, pulse repetition frequency, pulse width, and single pulse dose. Regarding biochemical factors, oxygen concentration is one of the key factors affecting radiobiological effects. The biological effects of FLASH-RT are also regulated by oxygen content, but it is worth investigating the differential responses of normal and tumor tissues to changes in oxygen content induced by FLASH-RT. The radiation sensitivity of different tissues and organs varies, leading to differences in the benefits gained from FLASH-RT. Additionally, the choice of study endpoints significantly impacts the conclusions of preclinical research on the biological effects of FLASH-RT. For instance, using different markers of DNA damage or analyzing acute versus late-phase indicators post-radiotherapy may yield different conclusions. This study will systematically analyze the effects of physical and biochemical parameters on the FLASH effect based on published experimental data, and the findings will provide useful suggestions for further research on FLASH biological effects.

Radiation-induced biological bystander effects have become a well-established phenomenon associated with the interaction of radiation with cells. These so-called bystander effects have been seen across a variety of end points for both high and low linear energy transfer (LET) radiations, utilizing a variety of dose rates and radiation sources. In this study, the effect of dose rate and different low LET sources on the bystander cell survival fraction (SF) was examined. The cell line investigated was the human keratinocyte HPV-G. The bystander response was measured via clonogenic assay after medium transfer protocol. Cells were irradiated using 60Co γ-rays and 20 MeV electrons at doses of 0.5, 5 and 10 Gy with varying dose rates. Both γ and electron irradiation decreased recipient SF at 0.5 Gy and 5 Gy, respectively. Subsequent recovery of the SF to control levels for 10 Gy was observed. There was no dose rate dependence for 60Co irradiation. A significant difference in the survival fraction was observed for electron irradiation at 10 Gy and a high dose rate. Furthermore, survival fractions were compared between 60Co and 20 MeV electron irradiations. This showed a significant increase in the survival fraction ‘recovery’ at 10 Gy for a 60Co dose rate of 1.1 Gy min−1 compared to 20 MeV electrons at 1.0 Gy min−1. No such difference was observed when comparing at higher dose rates. Lastly, increases in survival fraction at 10 Gy were abolished and the SF decreased by the plating of increased numbers of recipient cells. Such evidence may help gain insight into the nature and mechanism(s) surrounding bystander signal production, how these phenomena are tested and their eventual application in a clinical setting.

Monitoring of production process as a whole is currently possible with the progressive forms of computer simulation and displaying. The paper describes conceptual solution of improved diagnostic mapping of production process with use of the technology of augmented reality. The solution presents the powerful tool for visualization of diagnostic data useful mainly in the area of inspection, control and management of production operation.

High-energy electron, proton, neutron, photon and ion irradiation of semiconductor diodes and solar cells has long been a topic of considerable interest in the field of semiconductor device fabrication. The inevitable damage production during the process of irradiation is used to study and engineer the defects in semiconductors. In a strong radiation environment in space, the electrical performance of solar cells is degraded due to direct exposure to energetically charged particles. A considerable amount of work has been reported on the study of radiation damage in various solar cell materials and devices in the recent past. In most cases, high-energy heavy ions damage the material by producing a large amount of extended defects, but high-energy light ions are suitable for producing and modifying the intrinsic point defects. The defects can play a variety of electronically active roles that affect the electrical, structural and optical properties of a semiconductor. This review article aims to present an overview of the advancement of research in the modification of glassy semiconducting thin films using different types of radiations (light, proton and swift heavy ions). The work which has been done in our laboratory related to irradiation induced effects in semiconducting thin films will also be compared with the existing literature.

The formalism of form factors is the basis for the describing the coherent radiation of bunches that comprise relativistic charged particles. The general theory of coherent radiation for synchrotron and bremsstrahlung radiation, when radiation is generated directly by charged particles, but not by the material of a target, was developed long ago. However, there is no general model of coherent radiation for such polarization radiation as transition, diffraction and other types of radiation, when the radiation is generated by the material of a target polarized by the electromagnetic field of relativistic particles. This often causes the misapplication of the form factors of synchrotron radiation to other types of radiation. In this paper, we suggest the simplified algorithm for construction of form factors for different types of polarization radiation of relativistic electrons in the material of a target.

The development of Flexible Optoelectronic Organic Sensor for Infrared Detection (FOOS-IR), using an optically transparent substrate material and organic semiconductor materials, has been widely utilized by the electronic industry when producing new technological products. The greatest interest in studying organic semiconductor materials has been connected to its already known potential applications, such as: batteries, organic solar cells, flexible organic solar cells, organic light emitting diodes, organic sensors and others. Infrared is a type of electromagnetic radiation that has a frequency lower than that of red light and, therefore, is not within the visible electromagnetic spectrum. For this reason, this radiation cannot be perceived by the human eye. Infrared radiation originates from molecular vibration, which generates oscillations in the electrical charges that make up atoms and causes the emission of radiation, so this type of radiation is associated with heat. In this work, we developed a flexible organic optoelectronic sensor capable of detecting and determining the rate of radiation dose emitted by different sources of infrared radiation. The sensors were developed using optically transparent substrate with Nanostructured thin film layers of Poly(9-Vinylcarbazole) covered by a layer of Poly(P-Phenylene Vinylene) with nanostructured fullerene (C60) and Polyaniline-X1. The samples were characterized by UV-Vis Spectroscopy, Electrical Measurements and Scanning Electron Microscopy. With the results obtained from this study can be developed infrared sensitive OLEDs for applications in night vision systems and infrared technologies in security.

To investigate experimentally, if FLASH irradiation depletes oxygen within water for different radiation types such as photons, protons, and carbon ions. This study presents measurements of the oxygen consumption in sealed, 3D-printed water phantoms during irradiation with x-rays, protons, and carbon ions at varying dose rates up to 340Gy/s. The oxygen measurement was performed using an optical sensor allowing for noninvasive measurements. Oxygen consumption in water only depends on dose, dose rate, and linear energy transfer (LET) of the irradiation. The total amount of oxygen depleted per 10Gy was found to be 0.04% atm - 0.18% atm for 225kV photons, 0.04% atm - 0.25% atm for 224MeV protons, and 0.09% atm - 0.17% atm for carbon ions. Consumption depends on dose rate by an inverse power law and saturates for higher dose rates because of self-interactions of radicals. Higher dose rates yield lower oxygen consumption. No total depletion of oxygen was found for clinical doses. FLASH irradiation does consume oxygen, but not enough to deplete all the oxygen present. For higher dose rates, less oxygen was consumed than at standard radiotherapy dose rates. No total depletion was found for any of the analyzed radiation types for 10Gy dose delivery using FLASH.

Patients who undergo radiation therapy (RT), particularly fractionated courses, often develop lymphopenia. Clinical outcome for various cancer types, including brain tumors, identifies lymphopenia as a negative prognostic factor. The mechanism for RT induced lymphopenia is unclear. Simulated models suggest the volume of blood flowing through a radiation field could play a crucial role in death of radiosensitive lymphocytes. FLASH RT is ultrahigh dose rate administration of RT, &amp;gt;100 times faster dose rate than standard RT that has been observed to improve the therapeutic ratio in preclinical models by preferential normal tissue sparing. Hypothesized mechanisms include chemical reactions depleting oxygen in well oxygenated normal cells creating radioresistance, differing pro-inflammatory signaling impacting tumor and normal tissue, and less impact on circulating immune cells consequent to decreased proportion exposed during a treatment session which may enhance antineoplastic response. We designed the novel FLASH kV x-ray cabinet system for preclinical laboratory research (FLASH-SARRP) to deliver ultra-high dose rates up to 100 Gy/s as well as conventional dose rates of 1.0 Gy/s to facilitate comparative studies. A custom designed docking system was developed to reproducibly position and immobilize mouse for stereotactic radiation of the brain. Dose and dose rate measurements were performed with calibrated Gafchromic EBT3 film in solid water with 0.025 mm additional copper filter. FLASH-SARRP system delivered kV x-rays at an average dose-rate of 79.2±2.1Gy/s corresponding to 10 mm depth in the immobilized mouse brain. For the delivery of 15 Gy, treatment duration was 0.2 seconds for FLASH RT administration whereas it was 244 seconds for conventional dose rate. We successfully designed a high-precision platform to study partial brain x-ray FLASH effects in mice and studies are ongoing to assess differential impact on normal brain tissue, circulating cytokines, and immune cell populations for single dose and fractionated administration of FLASH and standard radiotherapy.

Brachytherapy (BT) deals with high gradient internal dose irradiation made up of a complex system where the source is placed nearby the tumor to destroy cancerous cells. A primary concern of clinical safety in BT is quality assurance to ensure the best matches between the delivered and prescribed doses targeting small volume tumors and sparing surrounding healthy tissues. Hence, the purpose of this study is to evaluate the performance of a point size inorganic scintillator detector (ISD) in terms of high dose rate brachytherapy (HDR-BT) treatment. A prototype of the dose verification system has been developed based on scintillating dosimetry to measure a high dose rate while using an 192 Ir BT source. The associated dose rate is measured in photons/s employing a highly sensitive photon counter (design data: 20 photons/s). Dose measurement was performed as a function of source-to-detector distance according to TG43U1 recommendations. Overall measurements were carried out inside water phantoms keeping the ISD along the BT needle; a minimum of 0.1cm distance was maintained between each measurement point. The planned dwell times were measured accurately from the difference of two adjacent times of transit. The ISD system performances were also evaluated in terms of dose linearity, energy dependency, scintillation stability, signal-to-noise ratio (SNR), and signal-to-background ratio (SBR). Finally, a comparison was presented between the ISD measurements and results obtained from TG43 reference dataset. The detection efficiency of the ISD was verified by measuring the planned dwell times at different dwell positions. Measurements demonstrated that the ISD has a perfectly linear behavior with dose rate (R2 =1) and shows high SNR (>35) and SBR (>36) values even at the lowest dose rate investigated at around 10cm from the source. Standard deviation (1σ) remains within 0.03% of signal magnitude, and less than 0.01% STEM signal was monitored at 0.1cm source-to-detector distance. Stability of 0.54% is achieved, and afterglow stays less than 1% of the total signal in all the irradiations. Excellent symmetrical behavior of the dose rate regarding source position was observed at different radiation planes. Finally, a comparison with TG-43 reference dataset shows that corrected measurements agreed with simulation data within 1.2% and 1.3%, and valid for the source-to-detector distance greater than 0.25cm. The proposed ISD in this study anticipated that the system could be promoted to validate with further clinical investigations. It allows an appropriate dose verification with dwell time estimation during source tracking and suitable dose measurement with a high spatial resolution both nearby (high dose gradient) and far (low dose gradient) from the source position.

Defect size dependence of critical current density enhancement for irradiated YBa 2Cu 3O 7−δ

Health Physics instruments are used to measure the risk which may be incurred by an individual exposed to a given radiation field. The response of the instrument sensors will differ markedly from actual human risk factors for a variety of reasons, and this requires the use of instrument modifications and conversion factors. The values of these conversion factors continue to be updated and will likely change in the future. To accommodate the effects of different types of radiation and new conversion and usage factors, new instruments should be able to determine the type, energy distribution, and direction of incoming radiation and then apply the proper weighting factors to determine relative human risk. Such instrumentation will need to utilize modern sensor elements and microprocessor electronics.

The effects of gamma rays and electron beams on the germination, outgrowth and the synthesis of protein and RNA of Bacillus pumilus spores were investigated to clarify the difference in the effects of the two types of radiations on bacterial spores. Gamma irradiation facilitated the germination to a slightly larger degree than electron irradiation. The outgrowth, growth and the synthesis of protein and RNA were inhibited by gamma irradiation to a greater extent than electron irradiation, when the spores were irradiated at the same dose. However, the effects of the two types of radiations were the same when the spores were irradiated with electron beams at a dose 30% higher than gamma rays. The results indicate that the effects of electron beams on bacterial spores and those of gamma rays are qualitatively the same but quantitatively different.

In this paper, we present a calculation method for the radiation response eigenvalue based on a monolithic active pixel sensor. By comparing the statistical eigenvalues of different regions of a pixel array in bright and dark environments, the linear relationship between the statistical eigenvalues obtained by different algorithms and the radiation dose rate was studied. Additionally, a dose rate characterization method based on the analysis of the eigenvalues of the MAPS response signal was proposed. The experimental results show that in the dark background environment, the eigenvalues had a good linear response in the region of any gray value in the range of 10–30. In the color images, due to the difference in the background gray values in adjacent color regions, the radiation response signal in dark regions was confused with the image information in bright regions, resulting in the loss of response signal and affecting the analysis results of the radiation response signal. For the low dose rate radiation field, as the radiation response signal was too weak and there was background dark noise, it was necessary to accumulate frame images to obtain a sufficient response signal. For the intense radiation field, the number of response events in a single image was very high, and only two consecutive frames of image data needed to be accumulated to meet the statistical requirements. The binarization method had a good characterization effect for the radiation at a low dose rate, and the binarization processing and the total gray value statistics of the response data at a high dose rate could better characterize the radiation dose rate. The calibration experiment results show that the binarization processing method can meet the requirements of using a MAPS for wide-range detection.