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Kasamatsu K, Matsuura T, Tanaka S, Takao S, Miyamoto N, Nam JM, Shirato H, Shimizu S, Umegaki K. The impact of dose delivery time on biological effectiveness in proton irradiation with various biological parameters. Med Phys 2020; 47:4644-4655. [PMID: 32652574 DOI: 10.1002/mp.14381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 05/31/2020] [Accepted: 06/19/2020] [Indexed: 12/14/2022] Open
Abstract
PURPOSE The purpose of this study is to evaluate the sublethal damage (SLD) repair effect in prolonged proton irradiation using the biophysical model with various cell-specific parameters of (α/β)x and T1/2 (repair half time). At present, most of the model-based studies on protons have focused on acute radiation, neglecting the reduction in biological effectiveness due to SLD repair during the delivery of radiation. Nevertheless, the dose-rate dependency of biological effectiveness may become more important as advanced treatment techniques, such as hypofractionation and respiratory gating, come into clinical practice, as these techniques sometimes require long treatment times. Also, while previous research using the biophysical model revealed a large repair effect with a high physical dose, the dependence of the repair effect on cell-specific parameters has not been evaluated systematically. METHODS Biological dose [relative biological effectiveness (RBE) × physical dose] calculation with repair included was carried out using the linear energy transfer (LET)-dependent linear-quadratic (LQ) model combined with the theory of dual radiation action (TDRA). First, we extended the dose protraction factor in the LQ model for the arbitrary number of different LET proton irradiations delivered sequentially with arbitrary time lags, referring to the TDRA. Using the LQ model, the decrease in biological dose due to SLD repair was systematically evaluated for spread-out Bragg peak (SOBP) irradiation in a water phantom with the possible ranges of both (α/β)x and repair parameters ((α/β)x = 1-15 Gy, T1/2 = 0-90 min). Then, to consider more realistic irradiation conditions, clinical cases of prostate, liver, and lung tumors were examined with the cell-specific parameters for each tumor obtained from the literature. Biological D99% and biological dose homogeneity coefficient (HC) were calculated for the clinical target volumes (CTVs), assuming dose-rate structures with a total irradiation time of 0-60 min. RESULTS The differences in the cell-specific parameters resulted in considerable variation in the repair effect. The biological dose reduction found at the center of the SOBP with 30 min of continuous irradiation varied from 1.13% to 14.4% with a T1/2 range of 1-90 min when (α/β)x is fixed as 10 Gy. It varied from 2.3% to 6.8% with an (α/β)x range of 1-15 Gy for a fixed value of T1/2 = 30 min. The decrease in biological D99% per 10 min was 2.6, 1.2, and 3.0% for the prostate, liver, and lung tumor cases, respectively. The value of the biological D99% reduction was neither in the order of (α/β)x nor prescribed dose, but both comparably contributed to the repair effect. The variation of HC was within the range of 0.5% for all cases; therefore, the dose distribution was not distorted. CONCLUSION The reduction in biological dose caused by the SLD repair largely depends on the cell-specific parameters in addition to the physical dose. The parameters should be considered carefully in the evaluation of the repair effect in prolonged proton irradiation.
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Affiliation(s)
- Koki Kasamatsu
- Graduate School of Biomedical Science and Engineering, Hokkaido University, Sapporo, Hokkaido, 0608638, Japan
| | - Taeko Matsuura
- Division of Quantum Science and Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, 0608628, Japan.,Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Hokkaido, 0608638, Japan.,Department of Medical Physics, Hokkaido University Hospital, Sapporo, Hokkaido, 0608648, Japan
| | - Sodai Tanaka
- Division of Quantum Science and Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, 0608628, Japan.,Department of Medical Physics, Hokkaido University Hospital, Sapporo, Hokkaido, 0608648, Japan
| | - Seishin Takao
- Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Hokkaido, 0608638, Japan.,Department of Medical Physics, Hokkaido University Hospital, Sapporo, Hokkaido, 0608648, Japan
| | - Naoki Miyamoto
- Division of Quantum Science and Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, 0608628, Japan.,Department of Medical Physics, Hokkaido University Hospital, Sapporo, Hokkaido, 0608648, Japan
| | - Jin-Min Nam
- Global Center for Biomedical Science and Engineering, Faculty of Medicine, Hokkaido University, Sapporo, Hokkaido, 0608648, Japan
| | - Hiroki Shirato
- Department of Proton Beam Therapy, Faculty of Medicine, Hokkaido University, Sapporo, Hokkaido, 0608648, Japan
| | - Shinichi Shimizu
- Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Hokkaido, 0608638, Japan.,Department of Medical Physics, Hokkaido University Hospital, Sapporo, Hokkaido, 0608648, Japan.,Department of Radiation Medical Science and Engineering, Faculty of Medicine, Hokkaido University, Sapporo, Hokkaido, 0608648, Japan
| | - Kikuo Umegaki
- Division of Quantum Science and Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, 0608628, Japan.,Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Hokkaido, 0608638, Japan.,Department of Medical Physics, Hokkaido University Hospital, Sapporo, Hokkaido, 0608648, Japan
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2
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Hill MA. Radiation Track Structure: How the Spatial Distribution of Energy Deposition Drives Biological Response. Clin Oncol (R Coll Radiol) 2020; 32:75-83. [PMID: 31511190 DOI: 10.1016/j.clon.2019.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/04/2019] [Accepted: 07/08/2019] [Indexed: 12/22/2022]
Abstract
Ionising radiation is incredibly effective at causing biological effects. This is due to the unique way energy is deposited along highly structured tracks of ionisation and excitation events, which results in correlation with sites of DNA damage from the nanometre to the micrometre scale. Correlation of these events along the track on the nanometre scale results in clustered damage, which not only results in the formation of DNA double-strand breaks (DSB), but also more difficult to repair complex DSB, which include additional damage within a few base pairs. The track structure varies significantly with radiation quality and the increase in relative biological effectiveness observed with increasing linear energy transfer in part corresponds to an increase in the probability and complexity of clustered DNA damage produced. Likewise, correlation over larger scales, associated with packing of DNA and associated chromosomes within the cell nucleus, can also have a major impact on the biological response. The proximity of the correlated damage along the track increases the probability of miss-repair through pairwise interactions resulting in an increase in probability and complexity of DNA fragments/deletions, mutations and chromosomal rearrangements. Understanding the mechanisms underlying the biological effectiveness of ionising radiation can provide an important insight into ways of increasing the efficacy of radiotherapy, as well as the risks associated with exposure. This requires a multi-scale approach for modelling, not only considering the physics of the track structure from the millimetre scale down to the nanometre scale, but also the structural packing of the DNA within the nucleus, the resulting chemistry in the context of the highly reactive environment of the nucleus, together with the subsequent biological response.
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Affiliation(s)
- M A Hill
- MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford, UK.
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3
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Asavei T, Bobeica M, Nastasa V, Manda G, Naftanaila F, Bratu O, Mischianu D, Cernaianu MO, Ghenuche P, Savu D, Stutman D, Tanaka KA, Radu M, Doria D, Vasos PR. Laser-driven radiation: Biomarkers for molecular imaging of high dose-rate effects. Med Phys 2019; 46:e726-e734. [PMID: 31357243 PMCID: PMC6899889 DOI: 10.1002/mp.13741] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 04/11/2019] [Accepted: 07/03/2019] [Indexed: 12/15/2022] Open
Abstract
Recently developed short‐pulsed laser sources garner high dose‐rate beams such as energetic ions and electrons, x rays, and gamma rays. The biological effects of laser‐generated ion beams observed in recent studies are different from those triggered by radiation generated using classical accelerators or sources, and this difference can be used to develop new strategies for cancer radiotherapy. High‐power lasers can now deliver particles in doses of up to several Gy within nanoseconds. The fast interaction of laser‐generated particles with cells alters cell viability via distinct molecular pathways compared to traditional, prolonged radiation exposure. The emerging consensus of recent literature is that the differences are due to the timescales on which reactive molecules are generated and persist, in various forms. Suitable molecular markers have to be adopted to monitor radiation effects, addressing relevant endogenous molecules that are accessible for investigation by noninvasive procedures and enable translation to clinical imaging. High sensitivity has to be attained for imaging molecular biomarkers in cells and in vivo to follow radiation‐induced functional changes. Signal‐enhanced MRI biomarkers enriched with stable magnetic nuclear isotopes can be used to monitor radiation effects, as demonstrated recently by the use of dynamic nuclear polarization (DNP) for biomolecular observations in vivo. In this context, nanoparticles can also be used as radiation enhancers or biomarker carriers. The radiobiology‐relevant features of high dose‐rate secondary radiation generated using high‐power lasers and the importance of noninvasive biomarkers for real‐time monitoring the biological effects of radiation early on during radiation pulse sequences are discussed.
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Affiliation(s)
- Theodor Asavei
- Extreme Light Infrastructure - Nuclear Physics ELI-NP, "Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania
| | - Mariana Bobeica
- Extreme Light Infrastructure - Nuclear Physics ELI-NP, "Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania
| | - Viorel Nastasa
- Extreme Light Infrastructure - Nuclear Physics ELI-NP, "Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania.,National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, RO-077125, Bucharest-Magurele, Romania
| | - Gina Manda
- Cellular and Molecular Medicine Department, "Victor Babes" National Institute of Pathology, 99-101 Splaiul Independentei, Bucharest, 050096, Romania
| | - Florin Naftanaila
- Carol Davila University of Medicine and Pharmacy Bucharest, Dr Carol Davila Central Mil University Emergency Hospital, 88th Mircea Vulcanescu Str, Bucharest, Romania.,Amethyst Radiotherapy Clinic, Dr Odaii 42, Otopeni, Romania
| | - Ovidiu Bratu
- Carol Davila University of Medicine and Pharmacy Bucharest, Dr Carol Davila Central Mil University Emergency Hospital, 88th Mircea Vulcanescu Str, Bucharest, Romania
| | - Dan Mischianu
- Carol Davila University of Medicine and Pharmacy Bucharest, Dr Carol Davila Central Mil University Emergency Hospital, 88th Mircea Vulcanescu Str, Bucharest, Romania
| | - Mihail O Cernaianu
- Extreme Light Infrastructure - Nuclear Physics ELI-NP, "Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania
| | - Petru Ghenuche
- Extreme Light Infrastructure - Nuclear Physics ELI-NP, "Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania
| | - Diana Savu
- Department of Life and Environmental Physics, Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania
| | - Dan Stutman
- Extreme Light Infrastructure - Nuclear Physics ELI-NP, "Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania.,National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, RO-077125, Bucharest-Magurele, Romania.,Johns Hopkins University, 3400 N Charles St, Baltimore, Maryland, 21218, USA
| | - Kazuo A Tanaka
- Extreme Light Infrastructure - Nuclear Physics ELI-NP, "Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania
| | - Mihai Radu
- Department of Life and Environmental Physics, Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania
| | - Domenico Doria
- Extreme Light Infrastructure - Nuclear Physics ELI-NP, "Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania.,Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, Belfast, BT7 1NN, United Kingdom
| | - Paul R Vasos
- Extreme Light Infrastructure - Nuclear Physics ELI-NP, "Horia Hulubei" National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, Bucharest-Magurele, Romania.,Research Institute of the University of Bucharest (ICUB), 36-46 B-dul M. Kogalniceanu, RO-050107, Bucharest, Romania
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Friedland W, Kundrát P, Schmitt E, Becker J, Ilicic K, Greubel C, Reindl J, Siebenwirth C, Schmid TE, Dollinger G. MODELING STUDIES ON DICENTRICS INDUCTION AFTER SUB-MICROMETER FOCUSED ION BEAM GRID IRRADIATION. RADIATION PROTECTION DOSIMETRY 2019; 183:40-44. [PMID: 30726972 DOI: 10.1093/rpd/ncy266] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 11/22/2018] [Indexed: 06/09/2023]
Abstract
The biophysical simulation tool PARTRAC contains modules for DNA damage response representing non-homologous end joining of DNA double-strand breaks (DSB) and the formation of chromosomal aberrations. Individual DNA ends from the induced DSB are followed regarding both their enzymatic processing and spatial mobility, as is needed for chromosome aberrations to arise via ligating broken ends from different chromosomes. In particular, by tracking the genomic locations of the ligated fragments and the positions of centromeres, the induction of dicentrics can be modeled. In recent experiments, the impact of spatial clustering of DNA damage on dicentric yields has been assessed in AL human-hamster hybrid cells: Defined numbers of 20 MeV protons (linear energy transfer, LET 2.6 keV/μm), 45 MeV Li ions (60 keV/μm) and 55 MeV C ions (310 keV/μm) focused to sub-μm spot sizes were applied with the ion microbeam SNAKE in diverse grid modes, keeping the absorbed dose constant. The impact of the μm-scaled spatial distribution of DSB (focusing effect) has thus been separated from nm-scaled DSB complexity (LET effect). The data provide a unique benchmark for the model calculations. Model and parameter refinements are described that enabled the simulations to largely reproduce both the LET-dependence and the focusing effect as well as the usual biphasic rejoining kinetics. The predictive power of the refined model has been benchmarked against dicentric yields for photon irradiation.
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Affiliation(s)
- W Friedland
- Department of Radiation Sciences, Institute of Radiation Protection, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstr. 1, Neuherberg, Germany
| | - P Kundrát
- Department of Radiation Sciences, Institute of Radiation Protection, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstr. 1, Neuherberg, Germany
| | - E Schmitt
- Department of Radiation Sciences, Institute of Radiation Protection, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstr. 1, Neuherberg, Germany
| | - J Becker
- Department of Radiation Sciences, Institute of Radiation Protection, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstr. 1, Neuherberg, Germany
| | - K Ilicic
- Department of Radiation Oncology, Technische Universität München, Ismaninger Str. 22, Munich, Germany
| | - C Greubel
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, Neubiberg, Germany
| | - J Reindl
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, Neubiberg, Germany
| | - C Siebenwirth
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, Neubiberg, Germany
| | - T E Schmid
- Department of Radiation Oncology, Technische Universität München, Ismaninger Str. 22, Munich, Germany
- Institute of Innovative Radiation Therapy, Department of Radiation Sciences, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstr. 1, Neuherberg, Germany
| | - G Dollinger
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, Neubiberg, Germany
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5
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DNA damage interactions on both nanometer and micrometer scale determine overall cellular damage. Sci Rep 2018; 8:16063. [PMID: 30375461 PMCID: PMC6207695 DOI: 10.1038/s41598-018-34323-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 09/30/2018] [Indexed: 02/06/2023] Open
Abstract
DNA double strand breaks (DSB) play a pivotal role for cellular damage, which is a hazard encountered in toxicology and radiation protection, but also exploited e.g. in eradicating tumors in radiation therapy. It is still debated whether and in how far clustering of such DNA lesions leads to an enhanced severity of induced damage. Here we investigate - using focused spots of ionizing radiation as damaging agent - the spatial extension of DNA lesion patterns causing cell inactivation. We find that clustering of DNA damage on both the nm and µm scale leads to enhanced inactivation compared to more homogeneous lesion distributions. A biophysical model interprets these observations in terms of enhanced DSB production and DSB interaction, respectively. We decompose the overall effects quantitatively into contributions from these lesion formation processes, concluding that both processes coexist and need to be considered for determining the resulting damage on the cellular level.
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6
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Hill MA. Track to the future: historical perspective on the importance of radiation track structure and DNA as a radiobiological target. Int J Radiat Biol 2018; 94:759-768. [PMID: 29219655 PMCID: PMC6113897 DOI: 10.1080/09553002.2017.1387304] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 09/22/2017] [Accepted: 09/27/2017] [Indexed: 12/04/2022]
Abstract
PURPOSE Understanding the mechanisms behind induced biological response following exposure to ionizing radiation is not only important in assessing the risk associated with human exposure, but potentially can help identify ways of improving the efficacy of radiotherapy. Over the decades, there has been much discussion on what is the key biological target for radiation action and its associated size. It was already known in the 1930s that microscopic features of radiation significantly influenced biological outcomes. This resulted in the development of classic target theory, leading to field of microdosimetry and subsequently nanodosimetry, studying the inhomogeneity and stochastics of interactions, along with the identification of DNA as a key target. CONCLUSIONS Ultimately, the biological response has been found to be dependent on the radiation track structure (spatial and temporal distribution of ionization and excitation events). Clustering of energy deposition on the nanometer scale has been shown to play a critical role in determining biological response, producing not just simple isolated DNA lesions but also complex clustered lesions that are more difficult to repair. The frequency and complexity of these clustered damage sites are typically found to increase with increasing LET. However in order to fully understand the consequences, it is important to look at the relative distribution of these lesions over larger dimensions along the radiation track, up to the micrometer scale. Correlation of energy deposition events and resulting sites of DNA damage can ultimately result in complex gene mutations and complex chromosome rearrangements following repair, with the frequency and spectrum of the resulting rearrangements critically dependent on the spatial and temporal distribution of these sites and therefore the radiation track. Due to limitations in the techniques used to identify these rearrangements it is likely that the full complexity of the genetic rearrangements that occur has yet to be revealed. This paper discusses these issues from a historical perspective, with many of these historical studies still having relevance today. These can not only cast light on current studies but guide future studies, especially with the increasing range of biological techniques available. So, let us build on past knowledge to effectively explore the future.
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Affiliation(s)
- Mark A. Hill
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, ORCRB Roosevelt Drive, Oxford, UK
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7
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Chaikh A, Calugaru V, Bondiau PY, Thariat J, Balosso J. Impact of the NTCP modeling on medical decision to select eligible patient for proton therapy: the usefulness of EUD as an indicator to rank modern photon vs proton treatment plans. Int J Radiat Biol 2018; 94:789-797. [DOI: 10.1080/09553002.2018.1486516] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Abdulhamid Chaikh
- Department of Radiation Oncology and Medical Physics, Grenoble Alpes University Hospital (CHUGA), Grenoble, France
- France HADRON National Research Infrastructure, IPNL, Lyon, France
- Laboratoire de Physique Corpusculaire IN2P3/ENSICAEN—UMR6534—Unicaen—Normandy University, Caen, France
| | | | | | - Juliette Thariat
- Laboratoire de Physique Corpusculaire IN2P3/ENSICAEN—UMR6534—Unicaen—Normandy University, Caen, France
- Department of Radiation Oncology, Centre François Baclesse, Caen, France
| | - Jacques Balosso
- Department of Radiation Oncology and Medical Physics, Grenoble Alpes University Hospital (CHUGA), Grenoble, France
- France HADRON National Research Infrastructure, IPNL, Lyon, France
- Department of Radiation Oncology, Centre François Baclesse, Caen, France
- University Grenoble-Alpes, Grenoble, France
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Ilicic K, Combs SE, Schmid TE. New insights in the relative radiobiological effectiveness of proton irradiation. Radiat Oncol 2018; 13:6. [PMID: 29338744 PMCID: PMC5771069 DOI: 10.1186/s13014-018-0954-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 01/05/2018] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Proton radiotherapy is a form of charged particle therapy that is preferentially applied for the treatment of tumors positioned near to critical structures due to their physical characteristics, showing an inverted depth-dose profile. The sparing of normal tissue has additional advantages in the treatment of pediatric patients, in whom the risk of secondary cancers and late morbidity is significantly higher. Up to date, a fixed relative biological effectiveness (RBE) of 1.1 is commonly implemented in treatment planning systems with protons in order to correct the physical dose. This value of 1.1 comes from averaging the results of numerous in vitro experiments, mostly conducted in the middle of the spread-out Bragg peak, where RBE is relatively constant. However, the use of a constant RBE value disregards the experimental evidence which clearly demonstrates complex RBE dependency on dose, cell- or tissue type, linear energy transfer and biological endpoints. In recent years, several in vitro studies indicate variations in RBE of protons which translate to an uncertainty in the biological effective dose delivery to the patient. Particularly for regions surrounding the Bragg peak, the more localized pattern of energy deposition leads to more complex DNA lesions. These RBE variations of protons bring the validity of using a constant RBE into question. MAIN BODY This review analyzes how RBE depends on the dose, different biological endpoints and physical properties. Further, this review gives an overview of the new insights based on findings made during the last years investigating the variation of RBE with depth in the spread out Bragg peak and the underlying differences in radiation response on the molecular and cellular levels between proton and photon irradiation. Research groups such as the Klinische Forschergruppe Schwerionentherapie funded by the German Research Foundation (DFG, KFO 214) have included work on this topic and the present manuscript highlights parts of the preclinical work and summarizes the research activities in this context. SHORT CONCLUSION In summary, there is an urgent need for more coordinated in vitro and in vivo experiments that concentrate on a realistic dose range of in clinically relevant tissues like lung or spinal cord.
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Affiliation(s)
- K Ilicic
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, 81675, München, Germany.,Institute of Innovative Radiotherapy, Helmholtz Zentrum München, Neuherberg, Germany
| | - S E Combs
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, 81675, München, Germany.,Institute of Innovative Radiotherapy, Helmholtz Zentrum München, Neuherberg, Germany.,Deutsches Konsortium für Translationale Krebsforschung (DKTK), Partner Site Munich, Munich, Germany
| | - T E Schmid
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, 81675, München, Germany. .,Institute of Innovative Radiotherapy, Helmholtz Zentrum München, Neuherberg, Germany.
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Meyer J, Stewart RD, Smith D, Eagle J, Lee E, Cao N, Ford E, Hashemian R, Schuemann J, Saini J, Marsh S, Emery R, Dorman E, Schwartz J, Sandison G. Biological and dosimetric characterisation of spatially fractionated proton minibeams. Phys Med Biol 2017; 62:9260-9281. [PMID: 29053105 DOI: 10.1088/1361-6560/aa950c] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The biological effectiveness of proton beams varies with depth, spot size and lateral distance from the beam central axis. The aim of this work is to incorporate proton relative biological effectiveness (RBE) and equivalent uniform dose (EUD) considerations into comparisons of broad beam and highly modulated proton minibeams. A Monte Carlo model of a small animal proton beamline is presented. Dose and variable RBE is calculated on a per-voxel basis for a range of energies (30-109 MeV). For an open beam, the RBE values at the beam entrance ranged from 1.02-1.04, at the Bragg peak (BP) from 1.3 to 1.6, and at the distal end of the BP from 1.4 to 2.0. For a 50 MeV proton beam, a minibeam collimator designed to produce uniform dose at the depth of the BP peak, had minimal impact on the open beam RBE values at depth. RBE changes were observed near the surface when the collimator was placed flush with the irradiated object, due to a higher neutron contribution derived from proton interactions with the collimator. For proton minibeams, the relative mean RBE weighted entrance dose (RWD) was ~25% lower than the physical mean dose. A strong dependency of the EUD with fraction size was observed. For 20 Gy fractions, the EUD varied widely depending on the radiosensitivity of the cells. For radiosensitive cells, the difference was up to ~50% in mean dose and ~40% in mean RWD and the EUD trended towards the valley dose rather than the mean dose. For comparative studies of uniform dose with spatially fractionated proton minibeams, EUD derived from a per-voxel RWD distribution is recommended for biological assessments of reproductive cell survival and related endpoints.
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Affiliation(s)
- Juergen Meyer
- Department of Radiation Oncology, University of Washington, 1959 NE Pacific Street, Box 356043, Seattle, WA 98195, United States of America
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10
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Increased cell survival and cytogenetic integrity by spatial dose redistribution at a compact synchrotron X-ray source. PLoS One 2017; 12:e0186005. [PMID: 29049300 PMCID: PMC5648152 DOI: 10.1371/journal.pone.0186005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Accepted: 09/22/2017] [Indexed: 11/24/2022] Open
Abstract
X-ray microbeam radiotherapy can potentially widen the therapeutic window due to a geometrical redistribution of the dose. However, high requirements on photon flux, beam collimation, and system stability restrict its application mainly to large-scale, cost-intensive synchrotron facilities. With a unique laser-based Compact Light Source using inverse Compton scattering, we investigated the translation of this promising radiotherapy technique to a machine of future clinical relevance. We performed in vitro colony-forming assays and chromosome aberration tests in normal tissue cells after microbeam irradiation compared to homogeneous irradiation at the same mean dose using 25 keV X-rays. The microplanar pattern was achieved with a tungsten slit array of 50 μm slit size and a spacing of 350 μm. Applying microbeams significantly increased cell survival for a mean dose above 2 Gy, which indicates fewer normal tissue complications. The observation of significantly less chromosome aberrations suggests a lower risk of second cancer development. Our findings provide valuable insight into the mechanisms of microbeam radiotherapy and prove its applicability at a compact synchrotron, which contributes to its future clinical translation.
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Friedland W, Schmitt E, Kundrát P, Dingfelder M, Baiocco G, Barbieri S, Ottolenghi A. Comprehensive track-structure based evaluation of DNA damage by light ions from radiotherapy-relevant energies down to stopping. Sci Rep 2017; 7:45161. [PMID: 28345622 PMCID: PMC5366876 DOI: 10.1038/srep45161] [Citation(s) in RCA: 118] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 02/21/2017] [Indexed: 12/15/2022] Open
Abstract
Track structures and resulting DNA damage in human cells have been simulated for hydrogen, helium, carbon, nitrogen, oxygen and neon ions with 0.25–256 MeV/u energy. The needed ion interaction cross sections have been scaled from those of hydrogen; Barkas scaling formula has been refined, extending its applicability down to about 10 keV/u, and validated against established stopping power data. Linear energy transfer (LET) has been scored from energy deposits in a cell nucleus; for very low-energy ions, it has been defined locally within thin slabs. The simulations show that protons and helium ions induce more DNA damage than heavier ions do at the same LET. With increasing LET, less DNA strand breaks are formed per unit dose, but due to their clustering the yields of double-strand breaks (DSB) increase, up to saturation around 300 keV/μm. Also individual DSB tend to cluster; DSB clusters peak around 500 keV/μm, while DSB multiplicities per cluster steadily increase with LET. Remarkably similar to patterns known from cell survival studies, LET-dependencies with pronounced maxima around 100–200 keV/μm occur on nanometre scale for sites that contain one or more DSB, and on micrometre scale for megabasepair-sized DNA fragments.
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Affiliation(s)
- W Friedland
- Institute of Radiation Protection, Department of Radiation Sciences, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany
| | - E Schmitt
- Institute of Radiation Protection, Department of Radiation Sciences, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany
| | - P Kundrát
- Institute of Radiation Protection, Department of Radiation Sciences, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany
| | - M Dingfelder
- Department of Physics, East Carolina University, Greenville, NC, USA
| | - G Baiocco
- Department of Physics, University of Pavia, Pavia, Italy
| | - S Barbieri
- Department of Physics, University of Pavia, Pavia, Italy
| | - A Ottolenghi
- Department of Physics, University of Pavia, Pavia, Italy
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12
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Schmid TE, Greubel C, Dollinger G, Schmid E. The influence of reference radiation photon energy on high-LET RBE: comparison of human peripheral lymphocytes and human-hamster hybrid A L cells. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2017; 56:79-87. [PMID: 28144741 DOI: 10.1007/s00411-016-0680-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 12/27/2016] [Indexed: 06/06/2023]
Abstract
The relative biological effectiveness (RBE) based on the induction of dicentrics in any cell type is principally an important information for the increasing application of high-LET radiation in cancer therapy. Since the standard system of human lymphocytes for measuring dicentrics are not compatible with our microbeam irradiation setup where attaching cells are essential, we used human-hamster hybrid AL cells which do attach on foils and fulfil the special experimental requirement for microbeam irradiations. In this work, the dose-response of AL cells to photons of different energy, 70 and 200 kV X-rays and 60Co γ-rays, is characterized and compared to human lymphocytes. The total number of induced dicentrics in AL cells is approximately one order of magnitude smaller. Despite the smaller α and β parameters of the measured linear-quadratic dose-response relationship, the α/β-ratio versus photon energy dependence is identical within the accuracy of measurement for AL cells and human lymphocytes. Thus, the influence of the reference radiation used for RBE determination is the same. For therapy relevant doses of 2 Gy (60Co equivalent), the difference in RBE is around 20% only. These findings indicate that the biological effectiveness in AL cells can give important information for human cells, especially for studies where attaching cells are essential.
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Affiliation(s)
- T E Schmid
- Institute of Innovative Radiotherapy, Helmholtz Zentrum München, Munich, Germany.
- Klinikum rechts der Isar, Department of Radiation Oncology, Technische Universität München, 81675, Munich, Germany.
| | - C Greubel
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577, Neubiberg, Germany
| | - G Dollinger
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577, Neubiberg, Germany
| | - E Schmid
- BioMedizinisches Centrum, Lehrstuhl Zellbiologie, Anatomie III, University of Munich, 80336, Munich, Germany
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13
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Reindl J, Girst S, Walsh DWM, Greubel C, Schwarz B, Siebenwirth C, Drexler GA, Friedl AA, Dollinger G. Chromatin organization revealed by nanostructure of irradiation induced γH2AX, 53BP1 and Rad51 foci. Sci Rep 2017; 7:40616. [PMID: 28094292 PMCID: PMC5240115 DOI: 10.1038/srep40616] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 12/07/2016] [Indexed: 11/28/2022] Open
Abstract
The spatial distribution of DSB repair factors γH2AX, 53BP1 and Rad51 in ionizing radiation induced foci (IRIF) in HeLa cells using super resolution STED nanoscopy after low and high linear energy transfer (LET) irradiation was investigated. 53BP1 and γH2AX form IRIF with same mean size of (540 ± 40) nm after high LET irradiation while the size after low LET irradiation is significantly smaller. The IRIF of both repair factors show nanostructures with partial anti-correlation. These structures are related to domains formed within the chromatin territories marked by γH2AX while 53BP1 is mainly situated in the perichromatin region. The nanostructures have a mean size of (129 ± 6) nm and are found to be irrespective of the applied LET and the labelled damage marker. In contrast, Rad51 shows no nanostructure and a mean size of (143 ± 13) nm independent of LET. Although Rad51 is surrounded by 53BP1 it strongly anti-correlates meaning an exclusion of 53BP1 next to DSB when decision for homologous DSB repair happened.
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Affiliation(s)
- Judith Reindl
- Angewandte Physik und Messtechnik, Universitaet der Bundeswehr Muenchen, Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany
| | - Stefanie Girst
- Angewandte Physik und Messtechnik, Universitaet der Bundeswehr Muenchen, Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany
| | - Dietrich W M Walsh
- Angewandte Physik und Messtechnik, Universitaet der Bundeswehr Muenchen, Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany.,Department of Radiation Oncology, Technische Universitaet Muenchen, 81675 Munich, Germany
| | - Christoph Greubel
- Angewandte Physik und Messtechnik, Universitaet der Bundeswehr Muenchen, Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany
| | - Benjamin Schwarz
- Angewandte Physik und Messtechnik, Universitaet der Bundeswehr Muenchen, Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany
| | - Christian Siebenwirth
- Angewandte Physik und Messtechnik, Universitaet der Bundeswehr Muenchen, Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany.,Department of Radiation Oncology, Technische Universitaet Muenchen, 81675 Munich, Germany
| | - Guido A Drexler
- Department of Radiation Oncology, Ludwig-Maximilians-Universitaet Muenchen, 80336 Munich, Germany
| | - Anna A Friedl
- Department of Radiation Oncology, Ludwig-Maximilians-Universitaet Muenchen, 80336 Munich, Germany
| | - Günther Dollinger
- Angewandte Physik und Messtechnik, Universitaet der Bundeswehr Muenchen, Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany
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14
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Hill MA. Fishing for radiation quality: chromosome aberrations and the role of radiation track structure. RADIATION PROTECTION DOSIMETRY 2015; 166:295-301. [PMID: 25883310 DOI: 10.1093/rpd/ncv151] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The yield of chromosome aberrations is not only dependent on dose but also on radiation quality, with high linear energy transfer (LET) typically having a greater biological effectiveness per unit dose than those of low-LET radiation. Differences in radiation track structure and cell morphology can also lead to quantitative differences in the spectra of the resulting chromosomal rearrangements, especially at low doses associated with typical human exposures. The development of combinatorial fluorescent labelling techniques (such as mFISH and mBAND) has helped to reveal the complexity of rearrangements, showing increasing complexity of observed rearrangements with increasing LET but has a resolution limited to ∼10 MBp. High-LET particles have not only been shown to produce clustered sites of DNA damage but also produce multiple correlated breaks along its path resulting in DNA fragments smaller than the resolution of these techniques. Additionally, studies have shown that the vast majority of radiation-induced HPRT mutations were also not detectable using fluorescent in situ hybridisation (FISH) techniques, with correlation of breaks along the track being reflected in the complexity of mutations, with intra- and inter-chromosomal insertions, and inversions occurring at the sites of some of the deletions. Therefore, the analysis of visible chromosomal rearrangements observed using current FISH techniques is likely to represent just the tip of the iceberg, considerably underestimating the extent and complexity of radiation induced rearrangements.
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Affiliation(s)
- M A Hill
- CRUK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, ORCRB Roosevelt Drive, Oxford OX3 7DQ, UK
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15
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Friedland W, Kundrát P, Schmitt E. Modelling proton bunches focussed to submicrometre scales: low-LET radiation damage in high-LET-like spatial structure. RADIATION PROTECTION DOSIMETRY 2015; 166:34-37. [PMID: 25883304 DOI: 10.1093/rpd/ncv146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Microbeam experiments approximating high-LET tracks by bunches of lower-LET particles focussed to submicrometre scales (Schmid et al. 2012, Phys. Med. Biol. 57, 5889) provide an unprecedented benchmark for models of biological effects of radiation. PARTRAC track structure-based Monte Carlo simulations have verified that focussed 20 MeV proton bunches resemble the radial dose distributions of single 55 MeV carbon ions as used in the experiments. However, the predicted yields of double-strand break and short (<1 kbp) DNA fragments by focussed protons correspond to homogeneous proton irradiation and are much smaller than for carbon tracks. The calculated yields of dicentrics overestimate the effect of focussing but reproduce the fourfold difference between carbon ions and homogeneously distributed protons. The extent to which focussed low-LET particles approximate high-LET radiation is limited by the achievable focussing: submicrometre focussing of proton bunches cannot reproduce local nanometre clustering, i.e. DNA damage complexity characteristic of high-LET radiation.
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Affiliation(s)
- W Friedland
- Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany
| | - P Kundrát
- Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany
| | - E Schmitt
- Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany
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16
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Schmid TE, Friedland W, Greubel C, Girst S, Reindl J, Siebenwirth C, Ilicic K, Schmid E, Multhoff G, Schmitt E, Kundrát P, Dollinger G. Sub-micrometer 20MeV protons or 45MeV lithium spot irradiation enhances yields of dicentric chromosomes due to clustering of DNA double-strand breaks. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2015; 793:30-40. [PMID: 26520370 DOI: 10.1016/j.mrgentox.2015.07.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 07/25/2015] [Indexed: 10/23/2022]
Abstract
In conventional experiments on biological effects of radiation types of diverse quality, micrometer-scale double-strand break (DSB) clustering is inherently interlinked with clustering of energy deposition events on nanometer scale relevant for DSB induction. Due to this limitation, the role of the micrometer and nanometer scales in diverse biological endpoints cannot be fully separated. To address this issue, hybrid human-hamster AL cells have been irradiated with 45MeV (60keV/μm) lithium ions or 20MeV (2.6keV/μm) protons quasi-homogeneously distributed or focused to 0.5×1μm(2) spots on regular matrix patterns (point distances up to 10.6×10.6μm), with pre-defined particle numbers per spot to provide the same mean dose of 1.7Gy. The yields of dicentrics and their distribution among cells have been scored. In parallel, track-structure based simulations of DSB induction and chromosome aberration formation with PARTRAC have been performed. The results show that the sub-micrometer beam focusing does not enhance DSB yields, but significantly affects the DSB distribution within the nucleus and increases the chance to form DSB pairs in close proximity, which may lead to increased yields of chromosome aberrations. Indeed, the experiments show that focusing 20 lithium ions or 451 protons per spot on a 10.6μm grid induces two or three times more dicentrics, respectively, than a quasi-homogenous irradiation. The simulations reproduce the data in part, but in part suggest more complex behavior such as saturation or overkill not seen in the experiments. The direct experimental demonstration that sub-micrometer clustering of DSB plays a critical role in the induction of dicentrics improves the knowledge on the mechanisms by which these lethal lesions arise, and indicates how the assumptions of the biophysical model could be improved. It also provides a better understanding of the increased biological effectiveness of high-LET radiation.
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Affiliation(s)
- T E Schmid
- Department of Radiation Oncology, Technische Universität München, Germany.
| | - W Friedland
- Institute of Radiation Protection, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany
| | - C Greubel
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany
| | - S Girst
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany
| | - J Reindl
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany
| | - C Siebenwirth
- Department of Radiation Oncology, Technische Universität München, Germany; Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany
| | - K Ilicic
- Department of Radiation Oncology, Technische Universität München, Germany
| | - E Schmid
- Department for Anatomy and Cell Biology, Ludwig-Maximilians Universität München, Germany
| | - G Multhoff
- Department of Radiation Oncology, Technische Universität München, Germany
| | - E Schmitt
- Institute of Radiation Protection, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany
| | - P Kundrát
- Institute of Radiation Protection, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany
| | - G Dollinger
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany
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17
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Microdosimetry spectra and relative biological effectiveness of 15 and 30 MeV proton beams. Appl Radiat Isot 2015; 97:101-105. [DOI: 10.1016/j.apradiso.2014.12.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 11/16/2014] [Accepted: 12/18/2014] [Indexed: 11/17/2022]
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18
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Drexler GA, Siebenwirth C, Drexler SE, Girst S, Greubel C, Dollinger G, Friedl AA. Live cell imaging at the Munich ion microbeam SNAKE - a status report. Radiat Oncol 2015; 10:42. [PMID: 25880907 PMCID: PMC4341815 DOI: 10.1186/s13014-015-0350-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 02/03/2015] [Indexed: 01/16/2023] Open
Abstract
Ion microbeams are important tools in radiobiological research. Still, the worldwide number of ion microbeam facilities where biological experiments can be performed is limited. Even fewer facilities combine ion microirradiation with live-cell imaging to allow microscopic observation of cellular response reactions starting very fast after irradiation and continuing for many hours. At SNAKE, the ion microbeam facility at the Munich 14 MV tandem accelerator, a large variety of biological experiments are performed on a regular basis. Here, recent developments and ongoing research projects at the ion microbeam SNAKE are presented with specific emphasis on live-cell imaging experiments. An overview of the technical details of the setup is given, including examples of suitable biological samples. By ion beam focusing to submicrometer beam spot size and single ion detection it is possible to target subcellular structures with defined numbers of ions. Focusing of high numbers of ions to single spots allows studying the influence of high local damage density on recruitment of damage response proteins.
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Affiliation(s)
- Guido A Drexler
- Department of Radiation Oncology, Ludwig-Maximilians-Universität München, Munich, Germany.
| | - Christian Siebenwirth
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, Munich, Germany.
| | - Sophie E Drexler
- Department of Radiation Oncology, Ludwig-Maximilians-Universität München, Munich, Germany.
| | - Stefanie Girst
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany.
| | - Christoph Greubel
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany.
| | - Günther Dollinger
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany.
| | - Anna A Friedl
- Department of Radiation Oncology, Ludwig-Maximilians-Universität München, Munich, Germany.
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Paganetti H. Relative biological effectiveness (RBE) values for proton beam therapy. Variations as a function of biological endpoint, dose, and linear energy transfer. Phys Med Biol 2014; 59:R419-72. [PMID: 25361443 DOI: 10.1088/0031-9155/59/22/r419] [Citation(s) in RCA: 591] [Impact Index Per Article: 59.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Proton therapy treatments are based on a proton RBE (relative biological effectiveness) relative to high-energy photons of 1.1. The use of this generic, spatially invariant RBE within tumors and normal tissues disregards the evidence that proton RBE varies with linear energy transfer (LET), physiological and biological factors, and clinical endpoint. Based on the available experimental data from published literature, this review analyzes relationships of RBE with dose, biological endpoint and physical properties of proton beams. The review distinguishes between endpoints relevant for tumor control probability and those potentially relevant for normal tissue complication. Numerous endpoints and experiments on sub-cellular damage and repair effects are discussed. Despite the large amount of data, considerable uncertainties in proton RBE values remain. As an average RBE for cell survival in the center of a typical spread-out Bragg peak (SOBP), the data support a value of ~1.15 at 2 Gy/fraction. The proton RBE increases with increasing LETd and thus with depth in an SOBP from ~1.1 in the entrance region, to ~1.15 in the center, ~1.35 at the distal edge and ~1.7 in the distal fall-off (when averaged over all cell lines, which may not be clinically representative). For small modulation widths the values could be increased. Furthermore, there is a trend of an increase in RBE as (α/β)x decreases. In most cases the RBE also increases with decreasing dose, specifically for systems with low (α/β)x. Data on RBE for endpoints other than clonogenic cell survival are too diverse to allow general statements other than that the RBE is, on average, in line with a value of ~1.1. This review can serve as a source for defining input parameters for applying or refining biophysical models and to identify endpoints where additional radiobiological data are needed in order to reduce the uncertainties to clinically acceptable levels.
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Affiliation(s)
- Harald Paganetti
- Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, 30 Fruit Street, Boston, MA 02114, USA
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