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Chen D, Motlagh SAO, Stappen FV, Labarbe R, Bell B, Kim M, Teo BKK, Dong L, Zou W, Diffenderfer ES. Secondary neutron dosimetry for conformal FLASH proton therapy. Med Phys 2024; 51:5081-5093. [PMID: 38597815 DOI: 10.1002/mp.17050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 03/12/2024] [Accepted: 03/13/2024] [Indexed: 04/11/2024] Open
Abstract
BACKGROUND Cyclotron-based proton therapy systems utilize the highest proton energies to achieve an ultra-high dose rate (UHDR) for FLASH radiotherapy. The deep-penetrating range associated with this high energy can be modulated by inserting a uniform plate of proton-stopping material, known as a range shifter, in the beam path at the nozzle to bring the Bragg peak within the target while ensuring high proton transport efficiency for UHDR. Aluminum has been recently proposed as a range shifter material mainly due to its high compactness and its mechanical properties. A possible drawback lies in the fact that aluminum has a larger cross-section of producing secondary neutrons compared to conventional plastic range shifters. Accordingly, an increase in secondary neutron contamination was expected during the delivery of range-modulated FLASH proton therapy, potentially heightening neutron-induced carcinogenic risks to the patient. PURPOSE We conducted neutron dosimetry using simulations and measurements to evaluate excess dose due to neutron exposure during UHDR proton irradiation with aluminum range shifters compared to plastic range shifters. METHODS Monte Carlo simulations in TOPAS were performed to investigate the secondary neutron production characteristics with aluminum range shifter during 225 MeV single-spot proton irradiation. The computational results were validated against measurements with a pair of ionization chambers in an out-of-field region ( ≤ $\le$ 30 cm) and with a Proton Recoil Scintillator-Los Alamos rem meter in a far-out-of-field region (0.5-2.5 m). The assessments were repeated with solid water slabs as a surrogate for the conventional range shifter material to evaluate the impact of aluminum on neutron yield. The results were compared with the International Electrotechnical Commission (IEC) standards to evaluate the clinical acceptance of the secondary neutron yield. RESULTS For a range modulation up to 26 cm in water, the maximum simulated and measured values of out-of-field secondary neutron dose equivalent per therapeutic dose with aluminum range shifter were found to be( 0.57 ± 0.02 ) mSv/Gy $(0.57\pm 0.02)\ \text{mSv/Gy}$ and( 0.46 ± 0.04 ) mSv/Gy $(0.46\pm 0.04)\ \text{mSv/Gy}$ , respectively, overall higher than the solid water cases (simulation:( 0.332 ± 0.003 ) mSv/Gy $(0.332\pm 0.003)\ \text{mSv/Gy}$ ; measurement:( 0.33 ± 0.03 ) mSv/Gy $(0.33\pm 0.03)\ \text{mSv/Gy}$ ). The maximum far out-of-field secondary neutron dose equivalent was found to be (8.8 ± 0.5 $8.8 \pm 0.5$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ and (1.62 ± 0.02 $1.62 \pm 0.02$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ for the simulations and rem meter measurements, respectively, also higher than the solid water counterparts (simulation: (3.3 ± 0.3 $3.3 \pm 0.3$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ ; measurement: (0.63 ± 0.03 $0.63 \pm 0.03$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ ). CONCLUSIONS We conducted simulations and measurements of secondary neutron production under proton irradiation at FLASH energy with range shifters. We found that the secondary neutron yield increased when using aluminum range shifters compared to conventional materials while remaining well below the non-primary radiation limit constrained by the IEC regulations.
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Affiliation(s)
- Dixin Chen
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | | | - Rudi Labarbe
- Ion Beam Applications S.A. (IBA), Louvain-la-Neuve, Belgium
| | - Beryl Bell
- Ion Beam Applications S.A. (IBA), Louvain-la-Neuve, Belgium
| | - Michele Kim
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Boon-Keng Kevin Teo
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Lei Dong
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Wei Zou
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Geser FA, Stabilini A, Christensen JB, Muñoz ID, Yukihara EG, Jäkel O, Vedelago J. A Monte Carlo study on the secondary neutron generation by oxygen ion beams for radiotherapy and its comparison to lighter ions. Phys Med Biol 2024; 69:015027. [PMID: 37995363 DOI: 10.1088/1361-6560/ad0f45] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 11/23/2023] [Indexed: 11/25/2023]
Abstract
Objective.To study the secondary neutrons generated by primary oxygen beams for cancer treatment and compare the results to those from primary protons, helium, and carbon ions. This information can provide useful insight into the positioning of neutron detectors in phantom for future experimental dose assessments.Approach.Mono-energetic oxygen beams and spread-out Bragg peaks were simulated using the Monte Carlo particle transport codesFLUktuierende KAskade, tool for particle simulation, and Monte Carlo N-Particle, with energies within the therapeutic range. The energy and angular distribution of the secondary neutrons were quantified.Main results.The secondary neutron spectra generated by primary oxygen beams present the same qualitative trend as for other primary ions. The energy distributions resemble continuous spectra with one peak in the thermal/epithermal region, and one other peak in the fast/relativistic region, with the most probable energy ranging from 94 up to 277 MeV and maximum energies exceeding 500 MeV. The angular distribution of the secondary neutrons is mainly downstream-directed for the fast/relativistic energies, whereas the thermal/epithermal neutrons present a more isotropic propagation. When comparing the four different primary ions, there is a significant increase in the most probable energy as well as the number of secondary neutrons per primary particle when increasing the mass of the primaries.Significance.Most previous studies have only presented results of secondary neutrons generated by primary proton beams. In this work, secondary neutrons generated by primary oxygen beams are presented, and the obtained energy and angular spectra are added as supplementary material. Furthermore, a comparison of the secondary neutron generation by the different primary ions is given, which can be used as the starting point for future studies on treatment plan comparison and secondary neutron dose optimisation. The distal penumbra after the maximum dose deposition appears to be a suitable location for in-phantom dose assessments.
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Affiliation(s)
- Federico A Geser
- Department of Radiation Safety and Security, Paul Scherrer Institute (PSI), Forschungsstrasse 111, Villigen PSI 5232, Switzerland
| | - Alberto Stabilini
- Department of Radiation Safety and Security, Paul Scherrer Institute (PSI), Forschungsstrasse 111, Villigen PSI 5232, Switzerland
| | - Jeppe B Christensen
- Department of Radiation Safety and Security, Paul Scherrer Institute (PSI), Forschungsstrasse 111, Villigen PSI 5232, Switzerland
| | - Iván D Muñoz
- Department of Physics and Astronomy, Heidelberg University, Im Neuenheimer Feld 226, Heidelberg D-69120, Germany
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - Eduardo G Yukihara
- Department of Radiation Safety and Security, Paul Scherrer Institute (PSI), Forschungsstrasse 111, Villigen PSI 5232, Switzerland
| | - Oliver Jäkel
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
- Heidelberg Ion Beam Therapy Center (HIT), Department of Radiation Oncology, University Hospital Heidelberg (UKHD), Im Neuenheimer Feld 450, Heidelberg D-69120, Germany
| | - José Vedelago
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
- Department of Radiation Oncology, Heidelberg University Hospital (UKHD), Im Neuenheimer Feld 400, Heidelberg D-69120, Germany
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Pino F, Delgado JC, Carturan SM, Mantovani G, Polo M, Fabris D, Maggioni G, Quaranta A, Moretto S. Novel flexible and conformable composite neutron scintillator based on fully enriched lithium tetraborate. Sci Rep 2023; 13:4799. [PMID: 36959323 PMCID: PMC10036633 DOI: 10.1038/s41598-023-31675-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 03/15/2023] [Indexed: 03/25/2023] Open
Abstract
Thermal neutron detection is a key subject for nuclear physics research and also in a wide variety of applications from homeland security to nuclear medicine. In this work, it is proposed a novel flexible and conformable composite thermal neutron scintillator based on a fully enriched Lithium Tetraborate preparation ([Formula: see text]Li[Formula: see text]B[Formula: see text]O[Formula: see text]) combined with a phosphorescent inorganic scintillator powder (ZnS:Ag), and is then distributed into a polydimethylsiloxane matrix. The proposed scintillator shows a good neutron detection efficiency (max. [Formula: see text] 57% with respect to the commercial EJ-420), an average light output of [Formula: see text] 9000 ph/neutron-capture, a remarkable insensitivity to [Formula: see text]-rays (Gamma Rejection Ratio <10[Formula: see text]), and an extraordinary flexibility, so as to reach extremely small curvature radii, down to 1.5 mm, with no signs of cracking or tearing. Its characteristics make it suitable to be employed in scenarios where non-standard geometries are needed, for example, to optimize the detector performance and/or maximize the detection efficiency. Finally, the response of a hybrid detector made of a plastic scintillator, wrapped with the proposed scintillator, coupled to a silicon photomultiplier array is described, and the excellent discrimination between [Formula: see text]-rays, fast and thermal neutrons resulting from data processing is demonstrated.
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Affiliation(s)
- Felix Pino
- Department of Physics and Astronomy "Galileo Galilei", University of Padova, Padua, Italy.
- Laboratori Nazionali di Legnaro, INFN, Legnaro, Italy.
| | - Jessica Carolina Delgado
- Department of Physics and Astronomy "Galileo Galilei", University of Padova, Padua, Italy
- Department of Physics and Earth Science, University of Ferrara, Ferrara, Italy
| | - Sara Maria Carturan
- Department of Physics and Astronomy "Galileo Galilei", University of Padova, Padua, Italy
- Laboratori Nazionali di Legnaro, INFN, Legnaro, Italy
| | - Giorgia Mantovani
- Department of Physics and Astronomy "Galileo Galilei", University of Padova, Padua, Italy
| | - Matteo Polo
- Department of Industrial Engineering, University of Trento, Povo, Italy
- Padova Section, INFN, Padua, Italy
| | | | - Gianluigi Maggioni
- Department of Physics and Astronomy "Galileo Galilei", University of Padova, Padua, Italy
- Laboratori Nazionali di Legnaro, INFN, Legnaro, Italy
| | - Alberto Quaranta
- Department of Industrial Engineering, University of Trento, Povo, Italy
- TIFPA-Trento Institute for Fundamental Physics and Applications, INFN, Povo, Italy
| | - Sandra Moretto
- Department of Physics and Astronomy "Galileo Galilei", University of Padova, Padua, Italy
- Padova Section, INFN, Padua, Italy
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Monte-Carlo techniques for radiotherapy applications II: equipment and source modelling, dose calculations and radiobiology. JOURNAL OF RADIOTHERAPY IN PRACTICE 2023. [DOI: 10.1017/s1460396923000080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/05/2023]
Abstract
Abstract
Introduction:
This is the second of two papers giving an overview of the use of Monte-Carlo techniques for radiotherapy applications.
Methods:
The first paper gave an introduction and introduced some of the codes that are available to the user wishing to model the different aspects of radiotherapy treatment. It also aims to serve as a useful companion to a curated collection of papers on Monte-Carlo that have been published in this journal.
Results and Conclusions:
This paper focuses on the application of Monte-Carlo to specific problems in radiotherapy. These include radiotherapy and imaging beam production, brachytherapy, phantom and patient dosimetry, detector modelling and track structure calculations for micro-dosimetry, nano-dosimetry and radiobiology.
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Vedelago J, Karger CP, Jäkel O. A review on reference dosimetry in radiation therapy with proton and light ion beams: status and impact of new developments. RADIAT MEAS 2022. [DOI: 10.1016/j.radmeas.2022.106844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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Becker A, Jäkel O, Vedelago J. Intensity threshold variation method in the post-irradiation analysis of Fluorescent Nuclear Track Detectors for neutron dosimetry. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2022.110257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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