1,721,020 research outputs found
EDUCATION AND TRAINING IN EUROPE TO SUPPORT LOW-DOSE RADIATION PHYSICS AND RADIOBIOLOGY
No full textThe success of any research programme is dependent on a continuing influx of new expertise, and continuing education to ensure the newest technologies and methods are exploited. In the past decade, a strategic approach has been used to build up the research expertise in the area of radiation protection and risk estimation. The High Level Expert Group (HLEG, www.hleg.de) in their 2009 report on European low-dose research asserted that education and training were key components in the development and maintenance of expertise for research into the risks from low-levels of ionising radiation. Following their recommendations, a Euratom-funded Network of Excellence (DoReMi, www.doremi-noe.net) was setup to develop a platform of European research institutions to coordinate the research programme and develop expertise in the area. We present here the activities initiated by DoReMi and currently continued by CONCERT (www.concert-h2020.eu) in support of education and training in the scientific areas underpinning radiation protection research
INVESTIGATION INTO THE PROBABILITY FOR MISCOUNTING IN FOCI-BASED ASSAYS
No full textWhen early radiation damage to biological systems is studied based on the formation of foci at the location of DNA double-strand breaks, the foci observed in irradiated cells either may be induced by ionizing radiation (IR) interactions or they may be due to other causes that lead to observation of foci also in unirradiated cells. Generally, to take account of the latter, additional samples are taken where the exposure to IR is skipped in the protocol. The data analysis relies on statistical independence of the frequency distributions of background and radiation-induced foci. In microscopy, however, the observed spatial patterns of foci are 2D projections of the spatial distributions of foci in the observed cell nuclei. This may lead to missing foci when scoring their number, particularly if projections of foci overlap or coincide. This paper investigates to what extent the statistical independence of the frequency distribution of the number of foci coming from IR interaction or other causes is compromised by foci overlapping
Neutrons in proton pencil beam scanning: Parameterization of energy, quality factors and RBE
No full textThe biological effectiveness of neutrons produced during proton therapy in
inducing cancer is unknown, but potentially large. In particular, since neutron
biological effectiveness is energy dependent, it is necessary to estimate,
besides the dose, also the energy spectra, in order to obtain quantities which
could be a measure of the biological effectiveness and test current models
and new approaches against epidemiological studies on cancer induction after
proton therapy. For patients treated with proton pencil beam scanning, this
work aims to predict the spatially localized neutron energies, the effective
quality factor, the weighting factor according to ICRP, and two RBE values,
the first obtained from the saturation corrected dose mean lineal energy and
the second from DSB cluster induction.
A proton pencil beam was Monte Carlo simulated using GEANT. Based
on the simulated neutron spectra for three different proton beam energies
a parameterization of energy, quality factors and RBE was calculated. The
pencil beam algorithm used for treatment planning at PSI has been extended
using the developed parameterizations in order to calculate the spatially
localized neutron energy, quality factors and RBE for each treated patient.
The parameterization represents the simple quantification of neutron
energy in two energy bins and the quality factors and RBE with a satisfying
precision up to 85 cm away from the proton pencil beam when compared
to the results based on 3D Monte Carlo simulations. The root mean square
error of the energy estimate between Monte Carlo simulation based results
and the parameterization is 3.9%. For the quality factors and RBE estimates
it is smaller than 0.9%. The model was successfully integrated into the PSI
treatment planning system.
It was found that the parameterizations for neutron energy, quality factors
and RBE were independent of proton energy in the investigated energy range
of interest for proton therapy. The pencil beam algorithm has been extended
using the developed parameterizations in order to calculate the neutron energy,
quality factor and RBE
Track Structure-Based Simulations on DNA Damage Induced by Diverse Isotopes
No full textDiverse isotopes such as 2H, 3He, 10Be, 11C and 14C occur in nuclear reactions in ion beam radiotherapy, in cosmic ray shielding, or are intentionally accelerated in dating techniques. However, only a few studies have specifically addressed the biological effects of diverse isotopes and were limited to energies of several MeV/u. A database of simulations with the PARTRAC biophysical tool is presented for H, He, Li, Be, B and C isotopes at energies from 0.5 GeV/u down to stopping. The doses deposited to a cell nucleus and also the yields per unit dose of single- and double-strand breaks and their clusters induced in cellular DNA are predicted to vary among diverse isotopes of the same element at energies < 1 MeV/u, especially for isotopes of H and He. The results may affect the risk estimates for astronauts in deep space missions or the models of biological effectiveness of ion beams and indicate that radiation protection in 14C or 10Be dating techniques may be based on knowledge gathered with 12C or 9Be
Track-structure simulations of energy deposition patterns to mitochondria and damage to their DNA
Full text linkPURPOSE:
Mitochondria have been implicated in initiating and/or amplifying the biological effects of ionizing radiation not mediated via damage to nuclear DNA. To help elucidate the underlying mechanisms, energy deposition patterns to mitochondria and radiation damage to their DNA have been modelled.
METHODS:
Track-structure simulations have been performed with PARTRAC biophysical tool for 60Co γ-rays and 5 MeV α-particles. Energy deposition to the cell's mitochondria has been analyzed. A model of mitochondrial DNA reflecting experimental information on its structure has been developed and used to assess its radiation-induced damage.
RESULTS:
Energy deposition to mitochondria is highly inhomogeneous, especially at low doses. Although a dose-dependent fraction of mitochondria sees no energy deposition at all, the hit ones receive rather high amounts of energy. Nevertheless, only little damage to mitochondrial DNA occurs, even at large doses.
CONCLUSION:
Mitochondrial DNA does not represent a critical target for radiation effects. Likely, the key role of mitochondria in radiation-induced biological effects arises from the communication between mitochondria and/or with the nucleus. Through this signaling, initial modifications in a few heavily hit mitochondria seem to be amplified to a massive long-term effect manifested in the whole cell or even tissue
Reaction mechanim interplay in determing the biological effectiveness of neutrons as a fucntion of energy
No full textPerturbation of cellular signaling cascades modulated by ionizing radiation and environmental stress
No full textCellular signaling plays a central role in the regulation of several cell functions, which can be perturbed by different external stimuli, including environmental stress and ionizing radiation. The dysregulation of intra- and extracellular mechanisms may alter the correct behaviour of cells. The aim of this work was to investigate the activation of strongly interlaced intracellular signaling pathways, following the exposure to low- and medium-doses of X-rays, with a focus on the mechanisms involved in the inflammatory- and apoptotic-related responses. In particular, the temporal dynamics of the ERK1/2 and PKB/AKT pathways and their possible dose dependences were investigated. The presented results indicate a clear dose dependence of such pathways only at early time points, suggesting a fast response of the system to X-rays and the need for further studies at shorter times after exposures
Perturbation of intra- and extra- cellular signalling cascade by ionizing radiation and environmental stress
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