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Background: The purpose was to assess the impact of irradiation technique type and beam energy on the mixed radiation field around the medical linear accelerator (linac) in terms of radiation quality and related radiation protection quantities. Materials and methods: Seven radiotherapeutic plans with Alderson-Rando anthropomorphic phantom [different techniques: conventional three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and intensity modulated arc therapy (IMAT), different beams: 6 MV or 18 MV, and their arrangements) were prepared for the case of prostate malignancy. Recombination chambers REM-2 and GW2 were positioned on the treatment couch 100 cm from the beam axis at the height of the isocentre. Recombination chambers REM-2 and GW2 were used for recombination index of radiation quality Q4 determination, measurement of total tissue dose Dt and calculation of gamma and neutron components to Dt. Estimation of Dt and Q4 allowed for the ambient dose equivalent H*(10) calculations for each plan. Results: For plans prepared with 6 MV beams, Q4 values within the limits of uncertainty were equal to one, which confirms the correctness of the measurement method. For plans implemented with 18 MV beams, the value of Q4 was in the range of 3.7-5.7. Comparison between treatment techniques indicates that the lowest exposure resulting from out-of-field doses comes from 6 MV IMAT (0.7 mSv), whereas the highest one is from 18 MV IMRT (55.1 mSv). Conclusion: With the recombination chambers technique it was confirmed that the choice of beam energy directly affects the generation of photoneutrons. The treatment plan technique can have a significant impact on the out-of-field dose. [ABSTRACT FROM AUTHOR]

The article is devoted to assessing the radiation quality formation of groundwater with anomalous excesses of 234U on example the Pre-Volga region (European part of Russia). It was found that exceeding the reference values of groundwater radiological toxicity in a number of cases is associated with anomalously high activity of 234U. Isotopic (2H, 18O) and chemical data indicate that the anomalous 234U/238U ratios are of cryogenic origin related to the effects of past climatic fluctuations on the aquifers. Such groundwater formed from thawed permafrost at extremely low uranium concentrations may have unsatisfactory radiological quality due to anomalous excesses of 234U. [ABSTRACT FROM AUTHOR]

Plants exhibit morphological plasticity in response to changes in the proportion of far-red radiation (FR). However, little is known about the response to a sudden increase of FR component. Cucumber seedlings were acclimatized to radiation without FR (FR-) for 1 - 5 d after germination, and then transferred to radiation containing FR (FR+) at levels similar to those in natural sunlight. Other seedlings were acclimatized to FR- or FR+, which was maintained continuously. The sudden increase in FR damaged the cotyledons and the first true leaf, especially when radiation was changed from FR- to FR+ at days 3 or 4 after germination. Necrosis of the damaged leaves may have resulted from inhibition of water flow in leaf xylem, because wilting and decreased stomatal conductance were observed simultaneously with leaf necrosis. Plants in the treatment groups that showed the most frequent damage showed two peaks in cotyledon elongation. This suggests that the leaves that had been acclimatized to FR- were easily damaged by the sudden promotion of leaf expansion caused by FR+.

Plants exhibit morphological plasticity in response to changes in the proportion of far-red radiation (FR). However, little is known about the response to a sudden increase of FR component. Cucumber seedlings were acclimatized to radiation without FR (FR-) for 1 - 5 d after germination, and then transferred to radiation containing FR (FR+) at levels similar to those in natural sunlight. Other seedlings were acclimatized to FR-or FR+, which was maintained continuously. The sudden increase in FR damaged the cotyledons and the first true leaf, especially when radiation was changed from FRto FR+ at days 3 or 4 after germination. Necrosis of the damaged leaves may have resulted from inhibition of water flow in leaf xylem, because wilting and decreased stomatal conductance were observed simultaneously with leaf necrosis. Plants in the treatment groups that showed the most frequent damage showed two peaks in cotyledon elongation. This suggests that the leaves that had been acclimatized to FR-were easily damaged by the sudden promotion of leaf expansion caused by FR+. [ABSTRACT FROM AUTHOR]

This work aims to establish some X-ray qualities recommended by the International Standard Organization (ISO) using the half-value layer (HVL) and Hp(10) dosimetry approaches. The HVL values of the following qualities N-60, N-80, N-100, N-150 and N-250 were determined using various attenuation layers. The obtained results were compared to those of reference X-ray beam qualities and a good agreement was found (difference less than 5% for all qualities). The GAMOS (Geant4-based Architecture for Medicine-Oriented Simulations) radiation transport Monte Carlo toolkit was employed to simulate the production of X-ray spectra. The characteristics HVLs, mean energy and the spectral resolution of simulated spectra have been calculated and turned out to be conform to the ISO reference ones (difference less than the limit allowed by ISO). Furthermore, the conversion coefficients from air kerma to personal dose equivalent for simulated and measured spectra were fairly similar (the maximum difference less than 4.2%).

• We analyzed differences in the effects induced by cranial exposure to protons or photons in a radiosensitive mouse model to identify and mechanistically understand differences in their biology. • Approximately the same apoptotic levels after protons or photons suggest a comparable early cellular response of the cerebellum to the two radiation types. • Similar kinetics of MB development were induced following irradiation with 3 Gy of protons or photons. Lens sparing by protons was observed, consistent with their physical properties. • Changes in expression of neurogenesis genes in hippocampus of similarly treated WT mice were radiation type-specific, mainly involving synaptic plasticity for protons and angiogenesis for photons. Notably, different features in neuroinflammation were observed, prevalently astrogliosis for protons and microgliosis for photons. Medulloblastoma (MB) is a common primary brain cancer in children. Proton therapy in pediatric MB is intensively studied and widely adopted. Compared to photon, proton radiations offer potential for reduced toxicity due to the characteristic Bragg Peak at the end of their path in tissue. The aim of this study was to compare the effects of irradiation with the same dose of protons or photons in Patched1 heterozygous knockout mice, a murine model predisposed to cancer and non-cancer radiogenic pathologies, including MB and lens opacity. TOP-IMPLART is a pulsed linear proton accelerator for proton therapy applications. We compared the long-term health effects of 3 Gy of protons or photons in neonatal mice exposed at postnatal day 2, during a peculiarly susceptible developmental phase of the cerebellum, lens, and hippocampus, to genotoxic stress. Experimental testing of the 5 mm Spread-Out Bragg Peak (SOBP) proton beam, through evaluation of apoptotic response, confirmed that both cerebellum and hippocampus were within the SOBP irradiation field. While no differences in MB induction were observed after irradiation with protons or photons, lens opacity examination confirmed sparing of the lens after proton exposure. Marked differences in expression of neurogenesis-related genes and in neuroinflammation, but not in hippocampal neurogenesis, were observed after irradiation of wild-type mice with both radiation types. Conclusion. In-vivo experiments with radiosensitive mouse models improve our mechanistic understanding of the dependence of brain damage on radiation quality, thus having important implications in translational research. [ABSTRACT FROM AUTHOR]

Different from conventional radiotherapy (CONV-RT), FLASH radiotherapy (FLASH-RT) delivers a single high dose at a mean dose rate ≥40 ​Gy/s in milliseconds to achieve similar tumor control to CONV-RT while sparing normal tissues from detrimental injury. It provides an intriguing perspective in improving clinical outcomes for tumor patients as well as a novel way to enhance the differential responses between normal and tumor tissues. However, its mechanisms remain largely unclear. In this paper, we review the currently available publications on FLASH-RT and parse the probable mechanisms of three major aspects including the production of reactive oxygen species, DNA damage response, and immunoreaction. Experiments specifically designed to disclose the intrinsic difference between normal and malignant cells in response to FLASH-RT and CONV-RT are necessary to prove these hypotheses.

Objective. There is an increasing interest in calculating and measuring linear energy transfer (LET) spectra in particle therapy in order to assess their impact in biological terms. As such, the accuracy of the particle fluence energy spectra becomes paramount. This study focuses on quantifying energy depositions of distinct proton, helium, carbon, and oxygen ion beams using a silicon pixel detector developed at CERN to determine LET spectra in silicon. Approach. While detection systems have been investigated in this pursuit, the scarcity of detectors capable of providing per-ion data with high spatial and temporal resolution remains an issue. This gap is where silicon pixel detector technology steps in, enabling online tracking of single-ion energy deposition. The used detector consisted of a 300 µ m thick silicon sensor operated in partial depletion. Main results. During post-processing, artifacts in the acquired signals were identified and methods for their corrections were developed. Subsequently, a correlation between measured and Monte Carlo-based simulated energy deposition distributions was performed, relying on a two-step recalibration approach based on linear and saturating exponential models. Despite the observed saturation effects, deviations were confined below 7% across the entire investigated range of track-averaged LET values in silicon from 0.77 keV µ m -1 to 93.16 keV µ m -1 . Significance. Simulated and measured mean energy depositions were found to be aligned within 7%, after applying artifact corrections. This extends the range of accessible LET spectra in silicon to clinically relevant values and validates the accuracy and reliability of the measurements. These findings pave the way towards LET-based dosimetry through an approach to translate these measurements to LET spectra in water. This will be addressed in a future study, extending functionality of treatment planning systems into clinical routine, with the potential of providing ion-beam therapy of utmost precision to cancer patients., (Creative Commons Attribution license.)

Cancer is an important long-term risk for astronauts exposed to protons and high-energy charged particles during travel and residence on asteroids, the moon, and other planets. NASA's Biomedical Critical Path Roadmap defines the carcinogenic risks of radiation exposure as one of four type I risks. A type I risk represents a demonstrated, serious problem with no countermeasure concepts, and may be a potential "show-stopper" for long duration spaceflight. Estimating the carcinogenic risks for humans who will be exposed to heavy ions during deep space exploration has very large uncertainties at present. There are no human data that address risk from extended exposure to complex radiation fields. The overarching goal in this area to improve risk modeling is to provide biological insight and mechanistic analysis of radiation quality effects on carcinogenesis. Understanding mechanisms will provide routes to modeling and predicting risk and designing countermeasures. This white paper reviews broad issues related to experimental models and concepts in space radiation carcinogenesis as well as the current state of the field to place into context recent findings and concepts derived from the NASA Space Radiation Program.

Purpose: The purpose of this study was to investigate for the first time the performance of a synthetic single crystal diamond detector for the microdosimetric characterization of clinical 62 MeV ocular therapy proton beams. Methods: A novel diamond microdosimeter with a well‐defined sensitive volume was fabricated and tested with a monoenergetic and spread‐out Bragg peak (SOBP) of the CATANA therapeutic proton beam in Catania, Italy. The whole sensitive volume of the detector has an active planar‐sectional area of 100 µm × 100 µm and a thickness of approximately 6.3 um. Microdosimetric measurements were performed at several water equivalent depths, corresponding to positions of clinical relevance. From the measured spectra, microdosimetric quantities such as the frequency mean lineal energy (y¯F), dose mean lineal energy (y¯D) as well as microdosimetric relative biological effectiveness (RBEµ) values were derived for each depth along both a pristine Bragg curve and SOBP. Finally, Geant4 Monte Carlo simulations were performed modeling the detector geometry and CATANA beamline in order to calculate the average linear energy transfer (LET) values in the diamond active layer and water. Results: The microdosimetric spectra acquired by the diamond microdosimeter show different shapes as a function of the water equivalent depths. No spectral distortion, due to pile‐up events and polarization effects, was observed. The experimental spectra have a very low detection threshold due to the electronic noise during the irradiation of about 1 keV/μm. The y¯F and y¯D values were in agreement with expected trends, showing a sharp increase in mean lineal energy at the distal edge of the Bragg peak. In addition, a good agreement between the mean lineal energy values and the calculated average LET ones was also observed. Finally, the RBE values evaluated with the diamond microdosimeter were in excellent agreement with those obtained with a mini tissue equivalent proportional counter as well as with radiobiological measurements in the same proton beam field. Conclusions: The microdosimetric performance of the tested synthetic single crystal diamond microdosimeter clearly indicates its suitability for quality assurance in clinical proton therapy beam. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the radiation quality dependence of the response of commercial semiconductor‐based dosimeters, and to estimate potential errors and uncertainties related to different measurement and calibration scenarios. Methods: All measurement results were compared to reference values measured at the IAEA dosimetry laboratory which is traceable to the international system of units (SI). Energy dependence of the response of eight semiconductor dosimeters were determined for five different anode‐filter combinations and tube voltages from 25 to 35 kV. For systems capable of deriving half value layer (HVL) and tube voltage from measurements, calibration coefficients for these measurements were calculated. Results: For six dosimeters, the maximum deviations from the reference value of the air kerma measurement were within ±5% as required by IEC 61674. Calibration coefficients for radiation qualities (anode‐filter and tube voltage combinations) relative to reference radiation quality Mo‐Mo 28 kV deviate up to 12%. HVL and tube voltage measurements exhibited deviations up to 11% and 10%, respectively. Conclusions: The air kerma responses of modern semiconductor dosimeters have a small energy dependence. However, no dosimeter tested complied with the accuracy limits stated by the manufacturer for tube voltage measurements, and only two dosimeters complied with the limits for HVL measurements. Absolute measurement of HVL and tube voltage with semiconductor dosimeters have to be verified for actual clinical radiation conditions on clinical mammography systems. Semiconductor dosimeters can be used for quality control measurements if individual calibration coefficients are available for the radiation condition applied. If other conditions are applied, additional uncertainty needs to be considered, particularly in the case of HVL and tube voltage measurements. [ABSTRACT FROM AUTHOR]

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: To investigate for the first time the potentialities of obtaining microdosimetric measurements in scanned clinical carbon‐ion beams using synthetic single crystal diamond detector and to verify the spectral conversion methods. Methods: Microdosimetric measurements were performed at different depths in a water phantom at the therapeutic scanned carbon‐ion beam of the National Center of Oncological Hadrontherapy (CNAO) in Pavia, using waterproof encapsulated diamond microdosimeter developed at "Tor Vergata" University. A monoenergetic carbon‐ion beam of 195 MeV/μ scanned over a square field of 2 × 2 cm2 was used. Experimental microdosimetric spectra were compared with those obtained with a propane‐filled Tissue Equivalent Proportional Counters (TEPCs) microdosimeter in the same facility at the same conditions. To this purpose, the spectra in diamond were converted to the spectra that would have been collected with a propane‐filled cylindrical sensitive volume by means of a novel analytic methodology, recently developed at MedAustron. Results: The microdosimetric spectra acquired by the diamond microdosimeter show different shapes in the 10 keV µm−1 ÷ 103 keV µm−1 lineal‐energy range at different water depths. In spite of the high counting rate, no spectral distortion, due to pile‐up events and polarization effects, were observed. The experimental spectra have a low detection threshold of about 6 keV µm−1 due to the electronic noise in the irradiation room. The comparison between the spectra converted to propane from diamond detector and the spectra collected directly with propane‐filled TEPC shows a good agreement in the whole lineal‐energy range. Furthermore this comparison confirms that diamond detector response is LET independent. The frequency‐ and dose‐mean lineal energy values were also assessed for all spectra. The frequency‐mean values obtained with diamond microdosimeter at different depths scales rather well with the absorbed dose values. Conclusions: Microdosimetric characterization of a synthetic single crystal diamond detector in high‐energy scanned carbon‐ion beams was performed. The results of the present study showed that this detector is suitable for microdosimetry of clinical carbon ion beams. In addition, the good agreement between the converted diamond spectra and those obtained with TEPC provides the first experimental validation of the spectra conversion methodologies as valuable tools for the comparison of spectra collected with different detectors. [ABSTRACT FROM AUTHOR]

Until recently, radiation effects have been considered to be mainly due to nuclear DNA damage and their management by repair mechanisms. However, molecular biology studies reveal that the outcomes of exposures to ionizing radiation (IR) highly depend on activation and regulation through other molecular components of organelles that determine cell survival and proliferation capacities. As typical epigenetic-regulated organelles and central power stations of cells, mitochondria play an important pivotal role in those responses. They direct cellular metabolism, energy supply and homeostasis as well as radiation-induced signaling, cell death, and immunological responses. This review is focused on how energy, dose and quality of IR affect mitochondria-dependent epigenetic and functional control at the cellular and tissue level. Low-dose radiation effects on mitochondria appear to be associated with epigenetic and non-targeted effects involved in genomic instability and adaptive responses, whereas high-dose radiation effects (>1 Gy) concern therapeutic effects of radiation and long-term outcomes involving mitochondria-mediated innate and adaptive immune responses. Both effects depend on radiation quality. For example, the increased efficacy of high linear energy transfer particle radiotherapy, e.g., C-ion radiotherapy, relies on the reduction of anastasis, enhanced mitochondria-mediated apoptosis and immunogenic (antitumor) responses.

The major part of energy deposition of ionizing radiation is caused by secondary electrons, independent of the primary radiation type. However, their spatial concentration and their spectral properties strongly depend on the primary radiation type and finally determine the pattern of molecular damage e.g. to biological targets as the DNA, and thus the final effect of the radiation exposure. To describe the physical and to predict the biological consequences of charged ion irradiation, amorphous track structure approaches have proven to be pragmatic and helpful. There, the local dose deposition in the ion track is equated by considering the emission and slowing down of the secondary electrons from the primary particle track. In the present work we exploit the model of Kiefer and Straaten and derive the spectral composition of secondary electrons as function of the distance to the track center. The spectral composition indicates differences to spectra of low linear energy transfer (LET) photon radiation, which we confirm by a comparison with Monte Carlo studies. We demonstrate that the amorphous track structure approach provides a simple tool for evaluating the spectral electron properties within the track structure. Predictions of the LET of electrons across the track structure as well as the electronic dose build-up effect are derived. Implications for biological effects and corresponding predicting models based on amorphous track structure are discussed., (Creative Commons Attribution license.)

• Adding far red to blue and red radiation increased leaf expansion and shoot mass. • Far-red effects were pronounced under a high blue-to-red ratio and low light. • Far-red enrichment increased radiation capture and thus promoted crop growth. • Inclusion of far-red radiation can be useful for indoor production of plants. Although outside the photosynthetic photon flux density (PPFD) waveband (400–700 nm), far-red (FR; 700–800 nm) radiation regulates photomorphogenesis and photochemistry, thereby meriting consideration in sole-source plant-lighting applications. We investigated how FR radiation interacted with the ratio of blue (B; 400–500 nm) to red (R; 600–700 nm) radiation (B:R) (experiment I) and PPFD (experiment II) to regulate seedling growth under sole-source lighting. We postulated that adding FR radiation to B + R radiation would increase leaf expansion and thus radiation capture to promote whole-plant photosynthesis, but that FR effects would depend on B:R and PPFD. In experiment I, lettuce (Lactuca sativa) 'Rex' and 'Cherokee' and basil (Ocimum basilicum) 'Genovese' were continuously irradiated by 180 μmol m–2 s–1 of B and/or R radiation [B 30 R 150 (low B:R), B 90 R 90 (high B:R), R 180 , or B 180 , where subscripts indicate respective photon flux densities in μmol m–2 s–1] with or without 30 μmol m–2 s–1 of FR radiation. Twelve and 16 days after seed sow for lettuce and basil, respectively, the addition of FR radiation increased leaf length and shoot weight of all crops with more pronounced impacts under high B:R than low B:R. It also increased root dry weight of basil and lettuce 'Cherokee'. Adding FR to B + R radiation reduced specific chlorophyll content in lettuce by 10–20%, but not in basil. Red pigmentation of lettuce 'Cherokee' increased with increasing B:R but decreased with the inclusion of FR radiation. In experiment II, we grew lettuce 'Rex' (for 8 days) and 'Rouxai' (for 10 days) under B 90 R 90 (low PPFD) or B 180 R 180 (high PPFD) at the same B:R with or without FR radiation at 30 or 75 μmol m–2 s–1. Additional FR radiation increased lettuce shoot weight and extension growth but reduced relative specific chlorophyll content under both PPFDs, although FR effects were attenuated under the high PPFD. Shoot dry weight, relative specific chlorophyll content, and red foliage pigmentation increased with PPFD. We conclude that FR enrichment improves photosynthetic radiation capture and thus promotes crop growth under sole-source lighting, and that its effects are especially pronounced under high B:R and a low PPFD. [ABSTRACT FROM AUTHOR]

Copyright of Momento: Revista de Física is the property of Universidad Nacional de Colombia, Departamento de Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is widely accepted that, in chromosome-aberration induction, the (mis-)rejoining probability of two chromosome fragments depends on their initial distance, r . However, several aspects of these “proximity effects” need to be clarified, also considering that they can vary with radiation quality, cell type and dose. A previous work performed by the BIANCA (BIophysical ANalysis of Cell death and chromosome Aberrations) biophysical model has suggested that, in human lymphocytes and fibroblasts exposed to low-LET radiation, an exponential function of the form exp(-r/r 0 ), which is consistent with free-end (confined) diffusion, describes proximity effects better than a Gaussian function. Herein, the investigation was extended to intermediate- and high-LET. Since the r 0 values (0.8 μm for lymphocytes and 0.7 μm for fibroblasts) were taken from the low-LET study, the results were obtained by adjusting only one model parameter, i.e. the yield of “Cluster Lesions” (CLs), where a CL was defined as a critical DNA damage producing two independent chromosome fragments. In lymphocytes, the exponential model allowed reproducing both dose-response curves for different aberrations (dicentrics, centric rings and excess acentrics), and values of F-ratio (dicentrics to centric rings) and G-ratio (interstitial deletions to centric rings). In fibroblasts, a good correspondence was found with the dose-response curves, whereas the G-ratio (and, to a lesser extent, the F-ratio) was underestimated. With increasing LET, F decreased and G increased in both cell types, supporting their role as “fingerprints” of high-LET exposure. A dose-dependence was also found at high LET, where F increased with dose and G decreased, possibly due to inter-track effects. We therefore conclude that, independent of radiation quality, in lymphocytes an exponential function can describe proximity effects at both inter- and intra-chromosomal level; on the contrary, in fibroblasts further studies (experimental and theoretical) are needed to explain the strong bias for intra-arm relative to inter-arm exchanges. [ABSTRACT FROM AUTHOR]

RQT is the standard for radiation conditions in computed tomography. It simulates a beam unrelieved of a CT scanner . The camera pencil ionization dosimeter is used in CT. The LNMRI become known characterization of RQT radiation conditions and the secondary standard calibration for type pencil ionisation chambers in its lab. The obtained beam has the characteristics required by IEC 61267. The results of the calibration presented combined uncertainty expanded to 95.45% from 2.22%.