Densely ionizing radiation has always been a main topic in radiobiology. In fact, α-particles and neutrons are sources of radiation exposure for the general population and workers in nuclear power ...plants. More recently, high-energy protons and heavy ions attracted a large interest for two applications: hadrontherapy in oncology and space radiation protection in manned space missions. For many years, studies concentrated on measurements of the relative biological effectiveness (RBE) of the energetic particles for different end points, especially cell killing (for radiotherapy) and carcinogenesis (for late effects). Although more recently, it has been shown that densely ionizing radiation elicits signalling pathways quite distinct from those involved in the cell and tissue response to photons. The response of the microenvironment to charged particles is therefore under scrutiny, and both the damage in the target and non-target tissues are relevant. The role of individual susceptibility in therapy and risk is obviously a major topic in radiation research in general, and for ion radiobiology as well. Particle radiobiology is therefore now entering into a new phase, where beyond RBE, the tissue response is considered. These results may open new applications for both cancer therapy and protection in deep space.
Motion in radiotherapy: particle therapy Bert, C; Durante, M
Physics in medicine & biology,
2011-Aug-21, 2011-08-21, 20110821, Letnik:
56, Številka:
16
Journal Article
Recenzirano
Charged particle beam radiotherapy requires dedicated measures to compensate for the dosimetric influence of inter- and intra-fractional target motion. Independent of the delivery technique, these ...measures have to incorporate the strong influence of the radiological depth on the delivered dose. For scanned beam delivery, interference effects of target motion and scanned beam can further cause under-dosage of the clinical target volume despite using margins. Within the scope of this review, published data with respect to motion management in scattered as well as scanned beam treatment delivery will be summarized. Based on a section covering the dosimetric impact of organ motion, motion management during treatment planning, patient positioning, treatment delivery and treatment validation will be summarized. For scattered beam delivery, the concepts and data are often based on clinical usage since treatment of moving tumors has been performed for several years. In the field of scanned beam delivery, the report focuses on the results of research on countermeasures of the interference effect. Clinical application of these techniques can be expected in the near future.
A possible dose enhancement effect by proton or electron irradiation in the vicinity of nanoparticles consisting of different high Z atomic materials has been investigated using the track structure ...Monte Carlo code TRAX. In the simulations, Fe, Ag, Gd, Pt and Au nanoparticles (r = 22 and 2 nm) were irradiated with monoenergetic proton beams at energies of therapeutic interest (2, 80 and 300 MeV) and 44 keV electrons. Due to the large number of electrons in atoms with high atomic numbers, many electrons can be released in Auger cascades in addition to the primary ionization process. The potential additional nanoscopic radial dose contributions in the presence of metallic nanoparticles are assessed by comparison with liquid water and water simulated with the same density as the metallic materials. We find a noticeable impact of Auger electrons emitted from the nanoparticles. Special focus has been given to the assessment of complete sets of low-energy electron cross sections for the nanoparticle materials.
Intensity modulated particle therapy (IMPT) with carbon ions can generate highly conformal treatment plans; however, IMPT is limited in robustness against range and positioning uncertainty. This is ...particularly true for moving targets, even though all motion states of a 4DCT are considered in 4D-IMPT. Here, we expand 4D-IMPT to include robust non-linear RBE-weighted optimization to explore its potential in improving plan robustness and sparing critical organs. In this study, robust 4D-optimization-based on worst-case optimization on 9 scenarios-was compared to conventional 4D-optimization with PTV margins using 4D dose calculation and robustness analysis for 21 uncertainty scenarios. Slice-by-slice rescanning was used for motion mitigation. Both 4D-optimization strategies were tested on a cohort of 8 multi-lesion lung cancer patients with the goal of prioritizing OAR sparing in a hypofractionated treatment plan. Planning objectives were to keep the OAR volume doses below corresponding limits while simultaneously achieve CTV coverage with D95% ≥ 95 %. For the conventional plans, average D95% was at 98.7% which fulfilled the target objective in 83.2% of scenarios. For the robust plans, average D95% was reduced to 97.6% which still fulfilled the target objective in 80.7% of cases, but led to significantly improved overall OAR sparing: Volume doses were below the limits in 96.2% of cases for the conventional and 99.5% for the robust plans. When considering the particularly critical smaller airways only, fulfillment rates could be increased from 76.2% to 96% for the robust plans. This study has shown that plan robustness of 4D-IMPT could be improved by using robust 4D-optimization, offering greater control over uncertainties in the actual delivered dose. In some cases, this required sacrificing target coverage for the benefit of better OAR sparing.
The Facility for Antiproton and Ion Research (FAIR) will be the accelerator-based flagship research facility in many basic sciences and their applications in Europe for the coming decades. FAIR will ...open up unprecedented research opportunities in hadron and nuclear physics, in atomic physics and nuclear astrophysics as well as in applied sciences like materials research, plasma physics and radiation biophysics with applications towards novel medical treatments and space science. FAIR is currently under construction as an international facility at the campus of the GSI Helmholtzzentrum for Heavy-Ion Research in Darmstadt, Germany. While the full science potential of FAIR can only be harvested once the new suite of accelerators and storage rings is completed and operational, some of the experimental detectors and instrumentation are already available and will be used starting in summer 2018 in a dedicated research program at GSI, exploiting also the significantly upgraded GSI accelerator chain. The current manuscript summarizes how FAIR will advance our knowledge in various research fields ranging from a deeper understanding of the fundamental interactions and symmetries in nature to a better understanding of the evolution of the Universe and the objects within.
Clinical Indications for Carbon Ion Radiotherapy Mohamad, O.; Yamada, S.; Durante, M.
Clinical oncology (Royal College of Radiologists (Great Britain)),
20/May , Letnik:
30, Številka:
5
Journal Article
Recenzirano
Compared with photon and proton therapy, carbon ion radiotherapy (CIRT) offers potentially superior dose distributions, which may permit dose escalation with the potential for improved sparing of ...adjacent normal tissues. CIRT has increased biological effectiveness leading to increased tumour killing compared with other radiation modalities. Here we review these biophysical properties and provide a comprehensive evaluation of the current clinical evidence available for different tumour types treated with CIRT. We suggest that patient selection for CIRT should move away from the traditional viewpoint, which confines use to deep-seated hypoxic tumours that are adjacent to radiosensitive structures. A more integrated translational approach is required for the future as densely ionising C-ions elicit a distinct signal response pathway compared with sparsely ionising X-rays. This makes CIRT a biologically distinct treatment compared with conventional radiotherapy.
Foundation species such as redwoods, seagrasses and corals are often long‐lived and clonal. Genets may consist of hundreds of members (ramets) and originated hundreds to thousands of years ago. As ...climate change and other stressors exert selection pressure on species, the demography of populations changes. Yet, because size does not indicate age in clonal organisms, demographic models are missing data necessary to predict the resilience of many foundation species. Here, we correlate somatic mutations with genet age of corals and provide the first, preliminary estimates of genet age in a colonial animal. We observed somatic mutations at five microsatellite loci in rangewide samples of the endangered coral, Acropora palmata (n = 3352). Colonies harboured 342 unique mutations in 147 genets. Genet age ranged from 30 to 838 years assuming a mutation rate of 1.195−04 per locus per year based on colony growth rates and 236 to 6500 years assuming a mutation rate of 1.542−05 per locus per year based on sea level changes to habitat availability. Long‐lived A. palmata genets imply a large capacity to tolerate past environmental change, and yet recent mass mortality events in A. palmata suggest that capacity is now being frequently exceeded.
Despite evidence that consumers appreciate freedom of choice, they also enjoy recommendation systems, subscription services, and marketplace encounters that seemingly occur by chance. This article ...proposes that enjoyment can, in some contexts, be higher than that in contexts involving choice. This occurs as a result of feelings of serendipity that arise when a marketplace encounter is positive, unexpected, and attributed to some degree of chance. A series of studies shows that feelings of serendipity positively influence an array of consumer outcomes, including satisfaction and enjoyment, perceptions of meaningfulness of an experience, likelihood of recommending a company, and likelihood of purchasing additional products from the company. The findings show that strategies based on serendipity are even more effective when consumers perceive that randomness played a role in how an encounter occurred, and not effective when the encounter is negative, the encounter occurs deterministically (i.e., planned by marketers to target consumers), and consumers perceive that they have enough knowledge to make their own choices. Altogether, this research suggests that marketers can influence customer satisfaction by structuring marketplace encounters to appear more serendipitous, as opposed to expected or entirely chosen by the consumer.
Natural fibre composite have a potential to be widely applied in the alternative to a fibreglass composites in sustainable energy impact absorption structures. In this study, the behaviour of hemp ...fibre epoxy composites subjected to a low-velocity impact loading, using an instrumented falling weight impact equipment, is presented. Two types of hemp reinforcements were used: unidirectional and bi-directional fabric and three balanced laminates (0 degree /90 degree ) different in thickness were studied: 4 plies, 8 plies, 12 plies. The results were compared. The laminates were fabricated by RIFT process using a common epoxy matrix. The reached volumetric fibre percentage Vf was not too high. It assumed a value of 34% for the unidirectional reinforcement and an average value of 30% for the bidirectional one. Some laminates were impregnated by PLA resin at the aim to obtain a completely natural system. The impact behaviour was analysed carrying out tests impacting square specimens, 100100mm, with a hemispherical tup geometry with a diameter of 19.8mm and a velocity of 4.0m/s. Both penetration and indentation tests were performed at the aim to investigate about the damage start and evolution. The impact induced damage, characterised by an optical microscope, includes matrix cracking, delamination, fibre breakage and fibre pullout. An interesting compressed central zone of the laminate under the impact point was noted.
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