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Pfuhl T, Friedrich T, Scholz M. Comprehensive comparison of local effect model IV predictions with the particle irradiation data ensemble. Med Phys 2021; 49:714-726. [PMID: 34766635 DOI: 10.1002/mp.15343] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 10/18/2021] [Accepted: 10/21/2021] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The increased relative biological effectiveness (RBE) of ions is one of the key benefits of ion radiotherapy compared to conventional radiotherapy with photons. To account for the increased RBE of ions during the process of ion radiotherapy treatment planning, a robust model for RBE predictions is indispensable. Currently, at several ion therapy centers the local effect model I (LEM I) is applied to predict the RBE, which varies with biological and physical impacting factors. After the introduction of LEM I, several model improvements were implemented, leading to the current version, LEM IV, which is systematically tested in this study. METHODS As a comprehensive RBE model should give consistent results for a large variety of ion species and energies, the particle irradiation data ensemble (PIDE) is used to systematically validate the LEM IV. The database covers over 1100 photon and ion survival experiments in form of their linear-quadratic parameters for a wide range of ion types and energies. This makes the database an optimal tool to challenge the systematic dependencies of the RBE model. After appropriate filtering of the database, 571 experiments were identified and used as test data. RESULTS The study confirms that the LEM IV reflects the RBE systematics observed in measurements well. It is able to reproduce the dependence of RBE on the linear energy transfer (LET) as well as on the αγ /βγ ratio for several ion species in a wide energy range. Additionally, the systematic quantitative analysis revealed precision capabilities and limits of the model. At lower LET values, the LEM IV tends to underestimate the RBE with an increasing underestimation with increasing atomic number of the ion. At higher LET values, the LEM IV overestimates the RBE for protons or helium ions, whereas the predictions for heavier ions match experimental data well. CONCLUSIONS The LEM IV is able to predict general RBE characteristics for several ion species in a broad energy range. The accuracy of the predictions is reasonable considering the small number of input parameters needed by the model. The detailed quantification of possible systematic deviations, however, enables to identify not only strengths but also limitations of the model. The gained knowledge can be used to develop model adjustments to further improve the model accuracy, which is on the way.
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Affiliation(s)
- Tabea Pfuhl
- Biophysics Department, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany.,Institute for Solid State Physics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Thomas Friedrich
- Biophysics Department, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany
| | - Michael Scholz
- Biophysics Department, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany
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Selva A, Bianchi A, Conte V. Experimental nanodosimetry: Track structure of 80 MeV boron ions. RADIAT MEAS 2021. [DOI: 10.1016/j.radmeas.2021.106660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Ngcezu SA, Rabus H. Investigation into the foundations of the track-event theory of cell survival and the radiation action model based on nanodosimetry. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2021; 60:559-578. [PMID: 34427743 PMCID: PMC8551112 DOI: 10.1007/s00411-021-00936-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 08/14/2021] [Indexed: 06/13/2023]
Abstract
This work aims at elaborating the basic assumptions behind the "track-event theory" (TET) and its derivate "radiation action model based on nanodosimetry" (RAMN) by clearly distinguishing between effects of tracks at the cellular level and the induction of lesions in subcellular targets. It is demonstrated that the model assumptions of Poisson distribution and statistical independence of the frequency of single and clustered DNA lesions are dispensable for multi-event distributions because they follow from the Poisson distribution of the number of tracks affecting the considered target volume. It is also shown that making these assumptions for the single-event distributions of the number of lethal and sublethal lesions within a cell would lead to an essentially exponential dose dependence of survival for practically relevant values of the absorbed dose. Furthermore, it is elucidated that the model equation used for consideration of repair within the TET is based on the assumption that DNA lesions induced by different tracks are repaired independently. Consequently, the model equation is presumably inconsistent with the model assumptions and requires an additional model parameter. Furthermore, the methodology for deriving model parameters from nanodosimetric properties of particle track structure is critically assessed. Based on data from proton track simulations it is shown that the assumption of statistically independent targets leads to the prediction of negligible frequency of clustered DNA damage. An approach is outlined how track structure could be considered in determining the model parameters, and the implications for TET and RAMN are discussed.
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Affiliation(s)
| | - Hans Rabus
- Physikalisch-Technische Bundesanstalt (PTB), 10587, Berlin, Germany.
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Vasi F, Schneider U. First measurements of ionization cluster-size distributions with a compact nanodosimeter. Med Phys 2021; 48:2566-2571. [PMID: 33506490 DOI: 10.1002/mp.14738] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 11/24/2020] [Accepted: 01/11/2021] [Indexed: 12/27/2022] Open
Abstract
PURPOSE A nanodosimeter is a type of detector which measures single ionizations in a small gaseous volume in order to obtain ionization cluster size probability distributions for characterization of radiation types. Working nanodosimeter detectors are usually bulky machines which require a lot of space. In this work, the authors present a compact ceramic nanodosimeter detector and report on first measurements of cluster size distributions of 5 MeV alpha particles. METHODS Single ionization measurements are achieved by applying a weak electric field to collect positive ions in a hole in a ceramic plate. Inside the ceramic plate, due to a strong electric field, the ions are accelerated and produce impact-ionizations. The resulting electron avalanche is detected in a read-out electrode. A Bayesian unfolding algorithm is then applied to the experimentally obtained cluster size distributions to reconstruct the true cluster size distributions. RESULTS Experimentally obtained cluster size distributions by the compact nanodosimeter detector are presented. The reconstructed cluster size distributions agreed well with Monte Carlo simulated cluster size distributions for small volumes (diameter = 2.5 nm). For larger volumes, discrepancies between the reconstructed cluster size distributions and cluster size distributions from Monte Carlo simulations were observed. CONCLUSIONS For the first time, ionization cluster size probability distributions could be obtained by a small and compact nanodosimeter detector. This signifies the achievement of a critical step toward the wide application of nanodosimetric characterization of radiation types including in clinical environments.
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Affiliation(s)
- Fabiano Vasi
- Radiotherapy Hirslanden, Zurich, Switzerland.,Department of Physics, University of Zurich, Zurich, Switzerland
| | - Uwe Schneider
- Radiotherapy Hirslanden, Zurich, Switzerland.,Department of Physics, University of Zurich, Zurich, Switzerland
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Schneider U, Vasi F, Schmidli K, Besserer J. A model of radiation action based on nanodosimetry and the application to ultra-soft X-rays. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2020; 59:439-450. [PMID: 32277259 DOI: 10.1007/s00411-020-00842-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 03/30/2020] [Indexed: 06/11/2023]
Abstract
A radiation action model based on nanodosimetry is presented. It is motivated by the finding that the biological effects of various types of ionizing radiation lack a consistent relation with absorbed dose. It is postulated that the common fundamental cause of these effects is the production of elementary sublesions (DSB), which are created at a rate that is proportional to the probability to produce more than two ionisations within a volume of 10 base pairs of the DNA. The concepts of nanodosimetry allow for a quantitative characterization of this process in terms of the cumulative probability F2. The induced sublesions can interact in two ways to produce lethal damage. First, if two or more sublesions accumulate in a locally limited spherical volume of 3-10 nm in diameter, clustered DNA damage is produced. Second, consequent interactions or rearrangements of some of the initial damage over larger distances (~ µm) can produce additional lethal damage. From the comparison of theoretical predictions deduced from this concept with experimental data on relative biological effectiveness, a cluster volume with a diameter of 7.5 nm could be determined. It is shown that, for electrons, the predictions agree well with experimental data over a wide energy range. The only free parameter needed to model cell survival is the intersection cross-section which includes all relevant cell-specific factors. Using ultra-soft X-rays it could be shown that the energy dependence of cell survival is directly governed by the nanodosimetric characteristics of the radiation track structure. The cell survival model derived in this work exhibits exponential cell survival at a high dose and a finite gradient of cell survival at vanishing dose, as well as the dependence on dose-rate.
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Affiliation(s)
- Uwe Schneider
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland.
- Radiotherapy Hirslanden, Witellikerstrasse 40, 8032, Zurich, Switzerland.
| | - Fabiano Vasi
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland
- Radiotherapy Hirslanden, Witellikerstrasse 40, 8032, Zurich, Switzerland
| | - Kevin Schmidli
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland
- Radiotherapy Hirslanden, Witellikerstrasse 40, 8032, Zurich, Switzerland
| | - Jürgen Besserer
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland
- Radiotherapy Hirslanden, Witellikerstrasse 40, 8032, Zurich, Switzerland
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Walsh L, Schneider U, Fogtman A, Kausch C, McKenna-Lawlor S, Narici L, Ngo-Anh J, Reitz G, Sabatier L, Santin G, Sihver L, Straube U, Weber U, Durante M. Research plans in Europe for radiation health hazard assessment in exploratory space missions. LIFE SCIENCES IN SPACE RESEARCH 2019; 21:73-82. [PMID: 31101157 DOI: 10.1016/j.lssr.2019.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Revised: 04/09/2019] [Accepted: 04/11/2019] [Indexed: 05/04/2023]
Abstract
The European Space Agency (ESA) is currently expanding its efforts in identifying requirements and promoting research towards optimizing radiation protection of astronauts. Space agencies use common limits for tissue (deterministic) effects on the International Space Station. However, the agencies have in place different career radiation exposure limits (for stochastic effects) for astronauts in low-Earth orbit missions. Moreover, no specific limits for interplanetary missions are issued. Harmonization of risk models and dose limits for exploratory-class missions are now operational priorities, in view of the short-term plans for international exploratory-class human missions. The purpose of this paper is to report on the activity of the ESA Topical Team on space radiation research, whose task was to identify the most pertinent research requirements for improved space radiation protection and to develop a European space radiation risk model, to contribute to the efforts to reach international consensus on dose limits for deep space. The Topical Team recommended ESA to promote the development of a space radiation risk model based on European-specific expertise in: transport codes, radiobiological modelling, risk assessment, and uncertainty analysis. The model should provide cancer and non-cancer radiation risks for crews implementing exploratory missions. ESA should then support the International Commission on Radiological Protection to harmonize international models and dose limits in deep space, and guarantee continuous support in Europe for accelerator-based research configured to improve the models and develop risk mitigation strategies.
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Affiliation(s)
- L Walsh
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland
| | - U Schneider
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland
| | | | - C Kausch
- GSI Helmholtzzentrum für Schwerionenforschung, Biophysics Department, Darmstadt, Germany
| | | | - L Narici
- Department of Physics, University Tor Vergata, and INFN, Roma-2 Section, Rome, Italy
| | - J Ngo-Anh
- ESA-ESTEC, Nordwijk, the Netherlands
| | - G Reitz
- Nuclear Physics Institute, Czech Academy of Sciences, Prague, Czechia; Radiation Biology, Institue for Aerospace Medicine, DLR, Cologne, Germany
| | - L Sabatier
- Fundamental Research Division, D3P, CEA, Paris-Saclay, France
| | - G Santin
- ESA-ESTEC, Nordwijk, the Netherlands
| | - L Sihver
- Atominstitut, Technische Universität Wien, Wien, Austria; MedAustron, Wiener Neustadt, Austria
| | | | - U Weber
- GSI Helmholtzzentrum für Schwerionenforschung, Biophysics Department, Darmstadt, Germany
| | - M Durante
- GSI Helmholtzzentrum für Schwerionenforschung, Biophysics Department, Darmstadt, Germany; Technische Universität Darmstadt, Darmstadt, Germany.
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