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Milluzzo G, De Napoli M, Di Martino F, Amato A, Del Sarto D, D'Oca MC, Marrale M, Masturzo L, Medina E, Okpuwe C, Pensavalle JH, Vignati A, Camarda M, Romano F. Comprehensive dosimetric characterization of novel silicon carbide detectors with UHDR electron beams for FLASH radiotherapy. Med Phys 2024. [PMID: 38772134 DOI: 10.1002/mp.17172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 04/26/2024] [Accepted: 04/27/2024] [Indexed: 05/23/2024] Open
Abstract
BACKGROUND The extremely fast delivery of doses with ultra high dose rate (UHDR) beams necessitates the investigation of novel approaches for real-time dosimetry and beam monitoring. This aspect is fundamental in the perspective of the clinical application of FLASH radiotherapy (FLASH-RT), as conventional dosimeters tend to saturate at such extreme dose rates. PURPOSE This study aims to experimentally characterize newly developed silicon carbide (SiC) detectors of various active volumes at UHDRs and systematically assesses their response to establish their suitability for dosimetry in FLASH-RT. METHODS SiC PiN junction detectors, recently realized and provided by STLab company, with different active areas (ranging from 4.5 to 10 mm2) and thicknesses (10-20 µm), were irradiated using 9 MeV UHDR pulsed electron beams accelerated by the ElectronFLASH linac at the Centro Pisano for FLASH Radiotherapy (CPFR). The linearity of the SiC response as a function of the delivered dose per pulse (DPP), which in turn corresponds to a specific instantaneous dose rate, was studied under various experimental conditions by measuring the produced charge within the SiC active layer with an electrometer. Due to the extremely high peak currents, an external customized electronic RC circuit was built and used in conjunction with the electrometer to avoid saturation. RESULTS The study revealed a linear response for the different SiC detectors employed up to 21 Gy/pulse for SiC detectors with 4.5 mm2/10 µm active area and thickness. These values correspond to a maximum instantaneous dose rate of 5.5 MGy/s and are indicative of the maximum achievable monitored DPP and instantaneous dose rate of the linac used during the measurements. CONCLUSIONS The results clearly demonstrate that the developed devices exhibit a dose-rate independent response even under extreme instantaneous dose rates and dose per pulse values. A systematic study of the SiC response was also performed as a function of the applied voltage bias, demonstrating the reliability of these dosimeters with UHDR also without any applied voltage. This demonstrates the great potential of SiC detectors for accurate dosimetry in the context of FLASH-RT.
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Affiliation(s)
- Giuliana Milluzzo
- National Institute of Nuclear Physics (INFN), Catania Division, Catania, Italy
| | - Marzio De Napoli
- National Institute of Nuclear Physics (INFN), Catania Division, Catania, Italy
| | - Fabio Di Martino
- Centro Pisano ricerca e implementazione clinica Flash Radiotherapy (CPFR@CISUP), Pisa, Italy
- Fisica Sanitaria, Azienda Ospedaliero Universitaria Pisa AOUP, Pisa, Italy
- National Institute of Nuclear Physics (INFN), Pisa Division, Pisa, Italy
| | - Antonino Amato
- STLab srl, Catania, Italy
- National Institute of Nuclear Physics (INFN), Laboratori Nazionali del Sud, Catania, Italy
| | - Damiano Del Sarto
- Centro Pisano ricerca e implementazione clinica Flash Radiotherapy (CPFR@CISUP), Pisa, Italy
- Fisica Sanitaria, Azienda Ospedaliero Universitaria Pisa AOUP, Pisa, Italy
| | - Maria Cristina D'Oca
- National Institute of Nuclear Physics (INFN), Catania Division, Catania, Italy
- Department of Physics and Chemistry "Emilio Segrè", University of Palermo, Palermo, Italy
| | - Maurizio Marrale
- National Institute of Nuclear Physics (INFN), Catania Division, Catania, Italy
- National Institute of Nuclear Physics (INFN), Laboratori Nazionali del Sud, Catania, Italy
| | - Luigi Masturzo
- Centro Pisano ricerca e implementazione clinica Flash Radiotherapy (CPFR@CISUP), Pisa, Italy
- Fisica Sanitaria, Azienda Ospedaliero Universitaria Pisa AOUP, Pisa, Italy
- SIT-Sordina, Aprilia, Italy
| | - Elisabetta Medina
- Physics Department, University of Torino, Torino, Italy
- National Institute of Nuclear Physics (INFN), Torino Division, Torino, Italy
| | - Chinonso Okpuwe
- National Institute of Nuclear Physics (INFN), Catania Division, Catania, Italy
- Physics Department, University of Catania, Catania, Italy
- Department of Physics, Federal University of Technology Owerri, Owerri, Nigeria
| | - Jake Harold Pensavalle
- Centro Pisano ricerca e implementazione clinica Flash Radiotherapy (CPFR@CISUP), Pisa, Italy
- Fisica Sanitaria, Azienda Ospedaliero Universitaria Pisa AOUP, Pisa, Italy
- SIT-Sordina, Aprilia, Italy
| | - Anna Vignati
- Physics Department, University of Torino, Torino, Italy
- National Institute of Nuclear Physics (INFN), Torino Division, Torino, Italy
| | | | - Francesco Romano
- National Institute of Nuclear Physics (INFN), Catania Division, Catania, Italy
- Particle Therapy Research Center (PARTREC), Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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Dai T, Sloop AM, Schönfeld A, Flatten V, Kozelka J, Hildreth J, Bill S, Sunnerberg JP, Clark MA, Jarvis L, Pogue BW, Bruza P, Gladstone DJ, Zhang R. Electron beam response corrections for an ultra-high-dose-rate capable diode dosimeter. Med Phys 2024. [PMID: 38762909 DOI: 10.1002/mp.17121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 04/29/2024] [Indexed: 05/21/2024] Open
Abstract
BACKGROUND Ultra-high-dose-rate (UHDR) electron beams have been commonly utilized in FLASH studies and the translation of FLASH Radiotherapy (RT) to the clinic. The EDGE diode detector has potential use for UHDR dosimetry albeit with a beam energy dependency observed. PURPOSE The purpose is to present the electron beam response for an EDGE detector in dependence on beam energy, to characterize the EDGE detector's response under UHDR conditions, and to validate correction factors derived from the first detailed Monte Carlo model of the EDGE diode against measurements, particularly under UHDR conditions. METHODS Percentage depth doses (PDDs) for the UHDR Mobetron were measured with both EDGE detectors and films. A detailed Monte Carlo (MC) model of the EDGE detector has been configured according to the blueprint provided by the manufacturer under an NDA agreement. Water/silicon dose ratios of EDGE detector for a series of mono-energetic electron beams have been calculated. The dependence of the water/silicon dose ratio on depth for a FLASH relevant electron beam was also studied. An analytical approach for the correction of PDD measured with EDGE detectors was established. RESULTS Water/silicon dose ratio decreased with decreasing electron beam energy. For the Mobetron 9 MeV UHDR electron beam, the ratio decreased from 1.09 to 1.03 in the build-up region, maintained in range of 0.98-1.02 at the fall-off region and raised to a plateau in value of 1.08 at the tail. By applying the corrections, good agreement between the PDDs measured by the EDGE detector and those measured with film was achieved. CONCLUSIONS Electron beam response of an UHDR capable EDGE detector was derived from first principles utilizing a sophisticated MC model. An analytical approach was validated for the PDDs of UHDR electron beams. The results demonstrated the capability of EDGE detector in measuring PDDs of UHDR electron beams.
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Affiliation(s)
- Tianyuan Dai
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan Shandong, China
| | - Austin M Sloop
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | | | | | | | | | - Simon Bill
- Sun Nuclear Corp, Melbourne, Florida, USA
| | - Jacob P Sunnerberg
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Megan A Clark
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Lesley Jarvis
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover, Lebanon, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
- Department of Medical Physics, Wisconsin Institutes for Medical Research, University of Wisconsin, Madison, Wisconsin, USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover, Lebanon, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Radiation Medicine, New York Medical College, Valhalla, New York, USA
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Pageot C, Zerouali K, Guillet D, Muir B, Renaud J, Lalonde A. The effect of electron backscatter and charge build up in media on beam current transformer signal for ultra-high dose rate (FLASH) electron beam monitoring. Phys Med Biol 2024; 69:105016. [PMID: 38640916 DOI: 10.1088/1361-6560/ad40f7] [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: 11/11/2023] [Accepted: 04/19/2024] [Indexed: 04/21/2024]
Abstract
Objective.Beam current transformers (BCT) are promising detectors for real-time beam monitoring in ultra-high dose rate (UHDR) electron radiotherapy. However, previous studies have reported a significant sensitivity of the BCT signal to changes in source-to-surface distance (SSD), field size, and phantom material which have until now been attributed to the fluctuating levels of electrons backscattered within the BCT. The purpose of this study is to evaluate this hypothesis, with the goal of understanding and mitigating the variations in BCT signal due to changes in irradiation conditions.Approach.Monte Carlo simulations and experimental measurements were conducted with a UHDR-capable intra-operative electron linear accelerator to analyze the impact of backscattered electrons on BCT signal. The potential influence of charge accumulation in media as a mechanism affecting BCT signal perturbation was further investigated by examining the effects of phantom conductivity and electrical grounding. Finally, the effectiveness of Faraday shielding to mitigate BCT signal variations is evaluated.Main Results.Monte Carlo simulations indicated that the fraction of electrons backscattered in water and on the collimator plastic at 6 and 9 MeV is lower than 1%, suggesting that backscattered electrons alone cannot account for the observed BCT signal variations. However, our experimental measurements confirmed previous findings of BCT response variation up to 15% for different field diameters. A significant impact of phantom type on BCT response was also observed, with variations in BCT signal as high as 14.1% when comparing measurements in water and solid water. The introduction of a Faraday shield to our applicators effectively mitigated the dependencies of BCT signal on SSD, field size, and phantom material.Significance.Our results indicate that variations in BCT signal as a function of SSD, field size, and phantom material are likely driven by an electric field originating in dielectric materials exposed to the UHDR electron beam. Strategies such as Faraday shielding were shown to effectively prevent these electric fields from affecting BCT signal, enabling reliable BCT-based electron UHDR beam monitoring.
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Affiliation(s)
- Charles Pageot
- École Polytechnique de Montréal, Montreal, QC, Canada
- Centre Hospitalier de l'Université de Montreal (CHUM), Montreal, QC, Canada
| | - Karim Zerouali
- Centre Hospitalier de l'Université de Montreal (CHUM), Montreal, QC, Canada
| | - Dominique Guillet
- Centre Hospitalier de l'Université de Montreal (CHUM), Montreal, QC, Canada
| | - Bryan Muir
- National Research Council, Ottawa, ON, Canada
| | | | - Arthur Lalonde
- Centre Hospitalier de l'Université de Montreal (CHUM), Montreal, QC, Canada
- Université de Montréal , Montreal, QC, Canada
- Centre de Recherche du Centre Hospitalier de l'Université de Montreal (CRCHUM), Montreal, QC, Canada
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Garibaldi C, Beddar S, Bizzocchi N, Tobias Böhlen T, Iliaskou C, Moeckli R, Psoroulas S, Subiel A, Taylor PA, Van den Heuvel F, Vanreusel V, Verellen D. Minimum and optimal requirements for a safe clinical implementation of ultra-high dose rate radiotherapy: A focus on patient's safety and radiation protection. Radiother Oncol 2024; 196:110291. [PMID: 38648991 DOI: 10.1016/j.radonc.2024.110291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 03/28/2024] [Accepted: 04/16/2024] [Indexed: 04/25/2024]
Affiliation(s)
- Cristina Garibaldi
- IEO, Unit of Radiation Research, European Institute of Oncology IRCCS, 20141 Milan, Italy.
| | - Sam Beddar
- The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Nicola Bizzocchi
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland
| | - Till Tobias Böhlen
- Institute of Radiation Physics, Lausanne University Hospital and Lausanne University, Lausanne, Switzerland
| | - Charoula Iliaskou
- Division of Medical Physics, Department of Radiation Oncology, University Medical Center Freiburg, 79106, Germany; German Cancer Consortium (DKTK), Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany
| | - Raphaël Moeckli
- Institute of Radiation Physics, Lausanne University Hospital and Lausanne University, Lausanne, Switzerland
| | - Serena Psoroulas
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland
| | - Anna Subiel
- National Physical Laboratory, Medical Radiation Science, Teddington, UK
| | - Paige A Taylor
- The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Frank Van den Heuvel
- Zuidwest Radiotherapeutisch Institute, Vlissingen, the Netherlands; Dept of Oncology, University of Oxford, Oxford, UK
| | - Verdi Vanreusel
- Iridium Netwerk, Antwerp University (Centre for Oncological Research, CORE), Antwerpen, Belgium; SCK CEN (Research in Dosimetric Applications), Mol, Belgium
| | - Dirk Verellen
- Iridium Netwerk, Antwerp University (Centre for Oncological Research, CORE), Antwerpen, Belgium
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Bateman JJ, Buchanan E, Corsini R, Farabolini W, Korysko P, Garbrecht Larsen R, Malyzhenkov A, Ortega Ruiz I, Rieker V, Gerbershagen A, Dosanjh M. Development of a novel fibre optic beam profile and dose monitor for very high energy electron radiotherapy at ultrahigh dose rates. Phys Med Biol 2024; 69:085006. [PMID: 38478998 DOI: 10.1088/1361-6560/ad33a0] [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: 12/04/2023] [Accepted: 03/13/2024] [Indexed: 04/04/2024]
Abstract
Objective. Very high energy electrons (VHEE) in the range of 50-250 MeV are of interest for treating deep-seated tumours with FLASH radiotherapy (RT). This approach offers favourable dose distributions and the ability to deliver ultra-high dose rates (UHDR) efficiently. To make VHEE-based FLASH treatment clinically viable, a novel beam monitoring technology is explored as an alternative to transmission ionisation monitor chambers, which have non-linear responses at UHDR. This study introduces the fibre optic flash monitor (FOFM), which consists of an array of silica optical fibre-based Cherenkov sensors with a photodetector for signal readout.Approach. Experiments were conducted at the CLEAR facility at CERN using 200 MeV and 160 MeV electrons to assess the FOFM's response linearity to UHDR (characterised with radiochromic films) required for FLASH radiotherapy. Beam profile measurements made on the FOFM were compared to those using radiochromic film and scintillating yttrium aluminium garnet (YAG) screens.Main results. A range of photodetectors were evaluated, with a complementary-metal-oxide-semiconductor (CMOS) camera being the most suitable choice for this monitor. The FOFM demonstrated excellent response linearity from 0.9 Gy/pulse to 57.4 Gy/pulse (R2= 0.999). Furthermore, it did not exhibit any significant dependence on the energy between 160 MeV and 200 MeV nor the instantaneous dose rate. Gaussian fits applied to vertical beam profile measurements indicated that the FOFM could accurately provide pulse-by-pulse beam size measurements, agreeing within the error range of radiochromic film and YAG screen measurements, respectively.Significance. The FOFM proves to be a promising solution for real-time beam profile and dose monitoring for UHDR VHEE beams, with a linear response in the UHDR regime. Additionally it can perform pulse-by-pulse beam size measurements, a feature currently lacking in transmission ionisation monitor chambers, which may become crucial for implementing FLASH radiotherapy and its associated quality assurance requirements.
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Affiliation(s)
- Joseph J Bateman
- John Adams Institute for Accelerator Science, Department of Physics, University of Oxford, Oxford, OX1 3RH, United Kingdom
| | - Emma Buchanan
- European Organization for Nuclear Research (CERN), Meyrin, 1211, Geneva, Switzerland
| | - Roberto Corsini
- European Organization for Nuclear Research (CERN), Meyrin, 1211, Geneva, Switzerland
| | - Wilfrid Farabolini
- European Organization for Nuclear Research (CERN), Meyrin, 1211, Geneva, Switzerland
| | - Pierre Korysko
- John Adams Institute for Accelerator Science, Department of Physics, University of Oxford, Oxford, OX1 3RH, United Kingdom
- European Organization for Nuclear Research (CERN), Meyrin, 1211, Geneva, Switzerland
| | - Robert Garbrecht Larsen
- European Organization for Nuclear Research (CERN), Meyrin, 1211, Geneva, Switzerland
- Particle Therapy Research Centre (PARTREC), Department of Radiation Oncology, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands
| | - Alexander Malyzhenkov
- European Organization for Nuclear Research (CERN), Meyrin, 1211, Geneva, Switzerland
| | - Iñaki Ortega Ruiz
- European Organization for Nuclear Research (CERN), Meyrin, 1211, Geneva, Switzerland
| | - Vilde Rieker
- European Organization for Nuclear Research (CERN), Meyrin, 1211, Geneva, Switzerland
- Department of Physics, University of Oslo, NO-0316 Blindern, Oslo, Norway
| | - Alexander Gerbershagen
- Particle Therapy Research Centre (PARTREC), Department of Radiation Oncology, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands
| | - Manjit Dosanjh
- John Adams Institute for Accelerator Science, Department of Physics, University of Oxford, Oxford, OX1 3RH, United Kingdom
- European Organization for Nuclear Research (CERN), Meyrin, 1211, Geneva, Switzerland
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Levin DS, Friedman PS, Ferretti C, Ristow N, Tecchio M, Litzenberg DW, Bashkirov V, Schulte R. A prototype scintillator real-time beam monitor for ultra-high dose rate radiotherapy. Med Phys 2024; 51:2905-2923. [PMID: 38456622 DOI: 10.1002/mp.17018] [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: 05/24/2023] [Revised: 02/24/2024] [Accepted: 02/26/2024] [Indexed: 03/09/2024] Open
Abstract
BACKGROUND FLASH Radiotherapy (RT) is an emergent cancer RT modality where an entire therapeutic dose is delivered at more than 1000 times higher dose rate than conventional RT. For clinical trials to be conducted safely, a precise and fast beam monitor that can generate out-of-tolerance beam interrupts is required. This paper describes the overall concept and provides results from a prototype ultra-fast, scintillator-based beam monitor for both proton and electron beam FLASH applications. PURPOSE A FLASH Beam Scintillator Monitor (FBSM) is being developed that employs a novel proprietary scintillator material. The FBSM has capabilities that conventional RT detector technologies are unable to simultaneously provide: (1) large area coverage; (2) a low mass profile; (3) a linear response over a broad dynamic range; (4) radiation hardness; (5) real-time analysis to provide an IEC-compliant fast beam-interrupt signal based on true two-dimensional beam imaging, radiation dosimetry and excellent spatial resolution. METHODS The FBSM uses a proprietary low mass, less than 0.5 mm water equivalent, non-hygroscopic, radiation tolerant scintillator material (designated HM: hybrid material) that is viewed by high frame rate CMOS cameras. Folded optics using mirrors enable a thin monitor profile of ∼10 cm. A field programmable gate array (FPGA) data acquisition system generates real-time analysis on a time scale appropriate to the FLASH RT beam modality: 100-1000 Hz for pulsed electrons and 10-20 kHz for quasi-continuous scanning proton pencil beams. An ion beam monitor served as the initial development platform for this work and was tested in low energy heavy-ion beams (86Kr+26 and protons). A prototype FBSM was fabricated and then tested in various radiation beams that included FLASH level dose per pulse electron beams, and a hospital RT clinic with electron beams. RESULTS Results presented in this report include image quality, response linearity, radiation hardness, spatial resolution, and real-time data processing. The HM scintillator was found to be highly radiation damage resistant. It exhibited a small 0.025%/kGy signal decrease from a 216 kGy cumulative dose resulting from continuous exposure for 15 min at a FLASH compatible dose rate of 237 Gy/s. Measurements of the signal amplitude versus beam fluence demonstrate linear response of the FBSM at FLASH compatible dose rates of >40 Gy/s. Comparison with commercial Gafchromic film indicates that the FBSM produces a high resolution 2D beam image and can reproduce a nearly identical beam profile, including primary beam tails. The spatial resolution was measured at 35-40 µm. Tests of the firmware beta version show successful operation at 20 000 Hz frame rate or 50 µs/frame, where the real-time analysis of the beam parameters is achieved in less than 1 µs. CONCLUSIONS The FBSM is designed to provide real-time beam profile monitoring over a large active area without significantly degrading the beam quality. A prototype device has been staged in particle beams at currents of single particles up to FLASH level dose rates, using both continuous ion beams and pulsed electron beams. Using a novel scintillator, beam profiling has been demonstrated for currents extending from single particles to 10 nA currents. Radiation damage is minimal and even under FLASH conditions would require ≥50 kGy of accumulated exposure in a single spot to result in a 1% decrease in signal output. Beam imaging is comparable to radiochromic films, and provides immediate images without hours of processing. Real-time data processing, taking less than 50 µs (combined data transfer and analysis times), has been implemented in firmware for 20 kHz frame rates for continuous proton beams.
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Affiliation(s)
- Daniel S Levin
- Department of Physics, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Claudio Ferretti
- Department of Physics, University of Michigan, Ann Arbor, Michigan, USA
| | - Nicholas Ristow
- Department of Physics, University of Michigan, Ann Arbor, Michigan, USA
| | - Monica Tecchio
- Department of Physics, University of Michigan, Ann Arbor, Michigan, USA
| | - Dale W Litzenberg
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan, USA
| | - Vladimir Bashkirov
- Division of Biomedical Engineering Sciences, Loma Linda University School of Medicine, Loma Linda, California, USA
| | - Reinhard Schulte
- Division of Biomedical Engineering Sciences, Loma Linda University School of Medicine, Loma Linda, California, USA
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Dai T, Sloop AM, Rahman MR, Sunnerberg JP, Clark MA, Young R, Adamczyk S, Von Voigts-Rhetz P, Patane C, Turk M, Jarvis L, Pogue BW, Gladstone DJ, Bruza P, Zhang R. First Monte Carlo beam model for ultra-high dose rate radiotherapy with a compact electron LINAC. Med Phys 2024. [PMID: 38493501 DOI: 10.1002/mp.17031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 03/04/2024] [Accepted: 03/04/2024] [Indexed: 03/19/2024] Open
Abstract
BACKGROUND FLASH radiotherapy based on ultra-high dose rate (UHDR) is actively being studied by the radiotherapy community. Dedicated UHDR electron devices are currently a mainstay for FLASH studies. PURPOSE To present the first Monte Carlo (MC) electron beam model for the UHDR capable Mobetron (FLASH-IQ) as a dose calculation and treatment planning platform for preclinical research and FLASH-radiotherapy (RT) clinical trials. METHODS The initial beamline geometry of the Mobetron was provided by the manufacturer, with the first-principal implementation realized in the Geant4-based GAMOS MC toolkit. The geometry and electron source characteristics, such as energy spectrum and beamline parameters, were tuned to match the central-axis percentage depth dose (PDD) and lateral profiles for the pristine beam measured during machine commissioning. The thickness of the small foil in secondary scatter affected the beam model dominantly and was fine tuned to achieve the best agreement with commissioning data. Validation of the MC beam modeling was performed by comparing the calculated PDDs and profiles with EBT-XD radiochromic film measurements for various combinations of applicators and inserts. RESULTS The nominal 9 MeV electron FLASH beams were best represented by a Gaussian energy spectrum with mean energy of 9.9 MeV and variance (σ) of 0.2 MeV. Good agreement between the MC beam model and commissioning data were demonstrated with maximal discrepancy < 3% for PDDs and profiles. Hundred percent gamma pass rate was achieved for all PDDs and profiles with the criteria of 2 mm/3%. With the criteria of 2 mm/2%, maximum, minimum and mean gamma pass rates were (100.0%, 93.8%, 98.7%) for PDDs and (100.0%, 96.7%, 99.4%) for profiles, respectively. CONCLUSIONS A validated MC beam model for the UHDR capable Mobetron is presented for the first time. The MC model can be utilized for direct dose calculation or to generate beam modeling input required for treatment planning systems for FLASH-RT planning. The beam model presented in this work should facilitate translational and clinical FLASH-RT for trials conducted on the Mobetron FLASH-IQ platform.
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Affiliation(s)
- Tianyuan Dai
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China
| | - Austin M Sloop
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | | | - Jacob P Sunnerberg
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Megan A Clark
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Ralph Young
- IntraOp Medical Corporation, Sunnyvale, California, USA
| | | | | | - Chris Patane
- IntraOp Medical Corporation, Sunnyvale, California, USA
| | - Michael Turk
- IntraOp Medical Corporation, Sunnyvale, California, USA
| | - Lesley Jarvis
- Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
- Department of Medical Physics, Wisconsin Institutes for Medical Research, University of Wisconsin, Madison, Wisconsin, USA
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Department of Radiation Medicine, New York Medical College, Valhalla, New York, USA
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8
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Levin DS, Friedman PS, Ferretti C, Ristow N, Tecchio M, Litzenberg DW, Bashkirov V, Schulte R. A Prototype Scintillator Real-Time Beam Monitor for Ultra-high Dose Rate Radiotherapy. ARXIV 2024:arXiv:2305.15306v3. [PMID: 37292473 PMCID: PMC10246063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Background FLASH Radiotherapy (RT) is an emergent cancer radiotherapy modality where an entire therapeutic dose is delivered at more than 1000 times higher dose rate than conventional RT. For clinical trials to be conducted safely, a precise and fast beam monitor that can generate out-of-tolerance beam interrupts is required. This paper describes the overall concept and provides results from a prototype ultra-fast, scintillator-based beam monitor for both proton and electron beam FLASH applications. Purpose A FLASH Beam Scintillator Monitor (FBSM) is being developed that employs a novel proprietary scintillator material. The FBSM has capabilities that conventional RT detector technologies are unable to simultaneously provide: 1) large area coverage; 2) a low mass profile; 3) a linear response over a broad dynamic range; 4) radiation hardness; 5) real-time analysis to provide an IEC-compliant fast beam-interrupt signal based on true two-dimensional beam imaging, radiation do-simetry and excellent spatial resolution. Methods The FBSM uses a proprietary low mass, less than 0.5 mm water equivalent, non-hygroscopic, radiation tolerant scintillator material (designated HM: hybrid material) that is viewed by high frame rate CMOS cameras. Folded optics using mirrors enable a thin monitor profile of ~10 cm. A field programmable gate array (FPGA) data acquisition system (DAQ) generates real-time analysis on a time scale appropriate to the FLASH RT beam modality: 100-1000 Hz for pulsed electrons and 10-20 kHz for quasi-continuous scanning proton pencil beams. An ion beam monitor served as the initial development platform for this work and was tested in low energy heavy-ion beams (86Kr+26 and protons). A prototype FBSM was fabricated and then tested in various radiation beams that included FLASH level dose per pulse electron beams, and a hospital radiotherapy clinic with electron beams. Results Results presented in this report include image quality, response linearity, radiation hardness, spatial resolution, and real-time data processing. The HM scintillator was found to be highly radiation damage resistant. It exhibited a small 0.025%/kGy signal decrease from a 216 kGy cumulative dose resulting from continuous exposure for 15 minutes at a FLASH compatible dose rate of 237 Gy/s. Measurements of the signal amplitude vs beam fluence demonstrate linear response of the FBSM at FLASH compatible dose rates of > 40 Gy/s. Comparison with commercial Gafchromic film indicates that the FBSM produces a high resolution 2D beam image and can reproduce a nearly identical beam profile, including primary beam tails. The spatial resolution was measured at 35-40 μm. Tests of the firmware beta version show successful operation at 20,000 Hz frame rate or 50 μs/frame, where the real-time analysis of the beam parameters is achieved in less than 1 μs. Conclusions The FBSM is designed to provide real-time beam profile monitoring over a large active area without significantly degrading the beam quality. A prototype device has been staged in particle beams at currents of single particles up to FLASH level dose rates, using both continuous ion beams and pulsed electron beams. Using a novel scintillator, beam profiling has been demonstrated for currents extending from single particles to 10 nA currents. Radiation damage is minimal and even under FLASH conditions would require ≥ 50 kGy of accumulated exposure in a single spot to result in a 1% decrease in signal output. Beam imaging is comparable to radiochromic films, and provides immediate images without hours of processing. Real-time data processing, taking less than 50 μs (combined data transfer and analysis times), has been implemented in firmware for 20 kHz frame rates for continuous proton beams.
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Affiliation(s)
- Daniel S Levin
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA
| | | | - Claudio Ferretti
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Nicholas Ristow
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Monica Tecchio
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Dale W Litzenberg
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Vladimir Bashkirov
- Division of Biomedical Engineering Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA
| | - Reinhard Schulte
- Division of Biomedical Engineering Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA
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9
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Liu K, Velasquez B, Schüler E. Technical note: High-dose and ultra-high dose rate (UHDR) evaluation of Al 2 O 3 :C optically stimulated luminescent dosimeter nanoDots and powdered LiF:Mg,Ti thermoluminescent dosimeters for radiation therapy applications. Med Phys 2024; 51:2311-2319. [PMID: 37991111 PMCID: PMC10939935 DOI: 10.1002/mp.16832] [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: 04/13/2023] [Revised: 09/11/2023] [Accepted: 10/25/2023] [Indexed: 11/23/2023] Open
Abstract
BACKGROUND Dosimetry in ultra-high dose rate (UHDR) electron beamlines poses a significant challenge owing to the limited usability of standard dosimeters in high dose and high dose-per-pulse (DPP) applications. PURPOSE In this study, Al2 O3 :C nanoDot optically stimulated luminescent dosimeters (OSLDs), single-use powder-based LiF:Mg,Ti thermoluminescent dosimeters (TLDs), and Gafchromic EBT3 film were evaluated at extended dose ranges (up to 40 Gy) in conventional dose rate (CONV) and UHDR beamlines to determine their usability for calibration and dose verification in the setting of FLASH radiation therapy. METHODS OSLDs and TLDs were evaluated against established dose-rate-independent Gafchromic EBT3 film with regard to the potential influence of mean dose rate, instantaneous dose rate, and DPP on signal response. The dosimeters were irradiated at CONV or UHDR conditions on a 9-MeV electron beam. Under UHDR conditions, different settings of pulse repetition frequency (PRF), pulse width (PW), and pulse amplitude were used to characterize the individual dosimeters' response in order to isolate their potential dependencies on dose, dose rate, and DPP. RESULTS The OSLDs, TLDs, and Gafchromic EBT3 film were found to be suitable at a dose range of up to 40 Gy without any indication of saturation in signal. The response of OSLDs and TLDs in UHDR conditions were found to be independent of mean dose rate (up to 1440 Gy/s), instantaneous dose rate (up to 2 MGy/s), and DPP (up to 7 Gy), with uncertainties on par with nominal values established in CONV beamlines (± 4%). In cross-comparing the response of OSLDs, TLDs and Gafchromic film at dose rates of 0.18-245 Gy/s, the coefficient of variation or relative standard deviation in the measured dose between the three dosimeters (inter-dosimeter comparison) was found to be within 2%. CONCLUSIONS We demonstrated the dynamic range of OSLDs, TLDs, and Gafchromic film to be suitable up to 40 Gy, and we developed a protocol that can be used to accurately translate the measured signal in each respective dosimeter to dose. OSLDs and powdered TLDs were shown to be viable for dosimetric measurement in UHDR beamlines, providing dose measurements with accuracies on par with Gafchromic EBT3 film and their concurrent use demonstrating a means for redundant dosimetry in UHDR conditions.
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Affiliation(s)
- Kevin Liu
- Division of Radiation Oncology, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- The University of Texas MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences, Houston, Texas, USA
| | - Brett Velasquez
- Division of Radiation Oncology, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Emil Schüler
- Division of Radiation Oncology, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- The University of Texas MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences, Houston, Texas, USA
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10
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Cetnar AJ, Jain S, Gupta N, Chakravarti A. Technical note: Commissioning of a linear accelerator producing ultra-high dose rate electrons. Med Phys 2024; 51:1415-1420. [PMID: 38159300 DOI: 10.1002/mp.16925] [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: 06/21/2023] [Revised: 12/12/2023] [Accepted: 12/18/2023] [Indexed: 01/03/2024] Open
Abstract
BACKGROUND Ultra-high dose rate radiation (UHDR) is being explored by researchers in promise of advancing radiation therapy treatments. PURPOSE This work presents the commissioning of Varian's Flash Extension for research (FLEX) conversion of a Clinac to deliver UHDR electrons. METHODS A Varian Clinac iX with the FLEX conversion was commissioned for non-clinical research use with 16 MeV UHDR (16H) energy. This involved addition of new hardware, optimizing the electron gun voltages, radiofrequency (RF) power, and steering coils in order to maximize the accelerated electron beam current, sending the beam through custom scattering foils to produce the UHDR with 16H beam. Profiles and percent depth dose (PDD) measurements for 16H were obtained using radiochromic film in a custom vertical film holder and were compared to 16 MeV conventional electrons (16C). Dose rate and dose per pulse (DPP) were calculated from measured dose in film. Linearity and stability were assessed using an Advanced Markus ionization chamber. RESULTS Energies for 16H and 16C had similar beam quality based on PDD measurements. Measurements at the head of the machine (61.3 cm SSD) with jaws set to 10×10 cm2 showed the FWHM of the profile as 7.2 cm, with 3.4 Gy as the maximum DPP and instantaneous dose rate of 8.1E5 Gy/s. Measurements at 100 cm SSD with 10 cm standard cone showed the full width at half max (FWHM) of the profile as 10.5 cm, 1.08 Gy as the maximum DPP and instantaneous dose rate of 2.E5 Gy/s. Machine output with number of pulses was linear (R = 1) from 1 to 99 delivered pulses. Output stability was measured within ±1% within the same session and within ±2% for daily variations. CONCLUSIONS The FLEX conversion of the Clinac is able to generate UHDR electron beams which are reproducible with beam properties similar to clinically used electrons at 16 MeV. Having a platform which can quickly transition between UHDR and conventional modes (<1 min) can be advantageous for future research applications.
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Affiliation(s)
- Ashley J Cetnar
- Department of Radiation Oncology, James Cancer Hospital and Solove Research Institute, The Ohio State University, Columbus, Ohio, USA
| | - Sagarika Jain
- Department of Radiation Oncology, James Cancer Hospital and Solove Research Institute, The Ohio State University, Columbus, Ohio, USA
| | - Nilendu Gupta
- Department of Radiation Oncology, James Cancer Hospital and Solove Research Institute, The Ohio State University, Columbus, Ohio, USA
| | - Arnab Chakravarti
- Department of Radiation Oncology, James Cancer Hospital and Solove Research Institute, The Ohio State University, Columbus, Ohio, USA
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11
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Oh K, Gallagher KJ, Hyun M, Schott D, Wisnoskie S, Lei Y, Hendley S, Wong J, Wang S, Graff B, Jenkins C, Rutar F, Ahmed M, McNeur J, Taylor J, Schmidt M, Senadheera L, Smith W, Umstadter D, Lele SM, Dai R, Jianghu (James) D, Yan Y, Su‐min Z. Initial experience with an electron FLASH research extension (FLEX) for the Clinac system. J Appl Clin Med Phys 2024; 25:e14159. [PMID: 37735808 PMCID: PMC10860433 DOI: 10.1002/acm2.14159] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 08/04/2023] [Accepted: 08/21/2023] [Indexed: 09/23/2023] Open
Abstract
PURPOSE Radiotherapy delivered at ultra-high-dose-rates (≥40 Gy/s), that is, FLASH, has the potential to effectively widen the therapeutic window and considerably improve the care of cancer patients. The underlying mechanism of the FLASH effect is not well understood, and commercial systems capable of delivering such dose rates are scarce. The purpose of this study was to perform the initial acceptance and commissioning tests of an electron FLASH research product for preclinical studies. METHODS A linear accelerator (Clinac 23EX) was modified to include a non-clinical FLASH research extension (the Clinac-FLEX system) by Varian, a Siemens Healthineers company (Palo Alto, CA) capable of delivering a 16 MeV electron beam with FLASH and conventional dose rates. The acceptance, commissioning, and dosimetric characterization of the FLEX system was performed using radiochromic film, optically stimulated luminescent dosimeters, and a plane-parallel ionization chamber. A radiation survey was conducted for which the shielding of the pre-existing vault was deemed sufficient. RESULTS The Clinac-FLEX system is capable of delivering a 16 MeV electron FLASH beam of approximately 1 Gy/pulse at isocenter and reached a maximum dose rate >3.8 Gy/pulse near the upper accessory mount on the linac gantry. The percent depth dose curves of the 16 MeV FLASH and conventional modes for the 10 × 10 cm2 applicator agreed within 0.5 mm at a range of 50% of the maximum dose. Their respective profiles agreed well in terms of flatness but deviated for field sizes >10 × 10 cm2 . The output stability of the FLASH system exhibited a dose deviation of <1%. Preliminary cell studies showed that the FLASH dose rate (180 Gy/s) had much less impact on the cell morphology of 76N breast normal cells compared to the non-FLASH dose rate (18 Gy/s), which induced large-size cells. CONCLUSION Our studies characterized the non-clinical Clinac-FLEX system as a viable solution to conduct FLASH research that could substantially increase access to ultra-high-dose-rate capabilities for scientists.
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Affiliation(s)
- Kyuhak Oh
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Megan Hyun
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Diane Schott
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Yu Lei
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Jeffrey Wong
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Shuo Wang
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Brendan Graff
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Frank Rutar
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Md Ahmed
- Varian Medical SystemsPalo AltoCaliforniaUSA
| | | | | | | | | | - Wendy Smith
- Varian Medical SystemsPalo AltoCaliforniaUSA
| | | | | | - Ran Dai
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Ying Yan
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Zhou Su‐min
- University of Nebraska Medical CenterOmahaNebraskaUSA
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12
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Konradsson E, Wahlqvist P, Thoft A, Blad B, Bäck S, Ceberg C, Petersson K. Beam control system and output fine-tuning for safe and precise delivery of FLASH radiotherapy at a clinical linear accelerator. Front Oncol 2024; 14:1342488. [PMID: 38304871 PMCID: PMC10830783 DOI: 10.3389/fonc.2024.1342488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 01/03/2024] [Indexed: 02/03/2024] Open
Abstract
Introduction We have previously adapted a clinical linear accelerator (Elekta Precise, Elekta AB) for ultra-high dose rate (UHDR) electron delivery. To enhance reliability in future clinical FLASH radiotherapy trials, the aim of this study was to introduce and evaluate an upgraded beam control system and beam tuning process for safe and precise UHDR delivery. Materials and Methods The beam control system is designed to interrupt the beam based on 1) a preset number of monitor units (MUs) measured by a monitor detector, 2) a preset number of pulses measured by a pulse-counting diode, or 3) a preset delivery time. For UHDR delivery, an optocoupler facilitates external control of the accelerator's thyratron trigger pulses. A beam tuning process was established to maximize the output. We assessed the stability of the delivery, and the independent interruption capabilities of the three systems (monitor detector, pulse counter, and timer). Additionally, we explored a novel approach to enhance dosimetric precision in the delivery by synchronizing the trigger pulse with the charging cycle of the pulse forming network (PFN). Results Improved beam tuning of gun current and magnetron frequency resulted in average dose rates at the dose maximum at isocenter distance of >160 Gy/s or >200 Gy/s, with or without an external monitor chamber in the beam path, respectively. The delivery showed a good repeatability (standard deviation (SD) in total film dose of 2.2%) and reproducibility (SD in film dose of 2.6%). The estimated variation in DPP resulted in an SD of 1.7%. The output in the initial pulse depended on the PFN delay time. Over the course of 50 measurements employing PFN synchronization, the absolute percentage error between the delivered number of MUs calculated by the monitor detector and the preset MUs was 0.8 ± 0.6% (mean ± SD). Conclusion We present an upgraded beam control system and beam tuning process for safe and stable UHDR electron delivery of hundreds of Gy/s at isocenter distance at a clinical linac. The system can interrupt the beam based on monitor units and utilize PFN synchronization for improved dosimetric precision in the dose delivery, representing an important advancement toward reliable clinical FLASH trials.
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Affiliation(s)
- Elise Konradsson
- Medical Radiation Physics, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Pontus Wahlqvist
- Radiation Physics, Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden
| | - Andreas Thoft
- Radiation Physics, Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden
| | - Börje Blad
- Medical Radiation Physics, Department of Clinical Sciences, Lund University, Lund, Sweden
- Radiation Physics, Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden
| | - Sven Bäck
- Medical Radiation Physics, Department of Clinical Sciences, Lund University, Lund, Sweden
- Radiation Physics, Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden
| | - Crister Ceberg
- Medical Radiation Physics, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Kristoffer Petersson
- Radiation Physics, Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden
- Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, United Kingdom
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13
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Pettinato S, Felici G, Galluzzo L, Rossi MC, Girolami M, Salvatori S. A readout system for highly sensitive diamond detectors for FLASH dosimetry. Phys Imaging Radiat Oncol 2024; 29:100538. [PMID: 38317851 PMCID: PMC10839766 DOI: 10.1016/j.phro.2024.100538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 01/13/2024] [Accepted: 01/15/2024] [Indexed: 02/07/2024] Open
Abstract
Accurate dosimetry of ultra-high dose-rate beams using diamond detectors remains challenging, primarily due to the elevated photocurrent peaks exceeding the input dynamics of precision electrometers. This work aimed at demonstrating the effectiveness of compact gated-integration electronics in conditioning the current peaks (>20 mA) generated by a highly sensitive (S ≃ 26 nC/Gy) custom-made diamond photoconductor under electron FLASH irradiation, as well as in real-time monitoring of beam dose and dose-rate. For the emerging FLASH technology, this study provided a new perspective on using commercially available diamond dosimeters with high sensitivity, currently employed in conventional radiotherapy.
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Affiliation(s)
- Sara Pettinato
- Dept. of Engineering, Niccolò Cusano University, via don Carlo Gnocchi 3, 00166 Rome, Italy
| | - Giuseppe Felici
- SIT – Sordina IORT Technologies S.p.A., Aprilia, Latina, Italy
| | | | - Maria Cristina Rossi
- Dept. of Industrial, Electronic, and Mechanical Engineering, Roma Tre University, Via Vito Volterra 62, 00146 Rome, Italy
| | - Marco Girolami
- Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM–CNR), Sede Secondaria di Montelibretti, Strada Provinciale 35/D n. 9, 00010 Montelibretti, Rome, Italy
| | - Stefano Salvatori
- Dept. of Engineering, Niccolò Cusano University, via don Carlo Gnocchi 3, 00166 Rome, Italy
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14
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Liu K, Holmes S, Hooten B, Schüler E, Beddar S. Evaluation of ion chamber response for applications in electron FLASH radiotherapy. Med Phys 2024; 51:494-508. [PMID: 37696271 PMCID: PMC10840726 DOI: 10.1002/mp.16726] [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: 02/20/2023] [Revised: 08/08/2023] [Accepted: 08/23/2023] [Indexed: 09/13/2023] Open
Abstract
Ion chambers are required for calibration and reference dosimetry applications in radiation therapy (RT). However, exposure of ion chambers in ultra-high dose rate (UHDR) conditions pertinent to FLASH-RT leads to severe saturation and ion recombination, which limits their performance and usability. The purpose of this study was to comprehensively evaluate a set of commonly used commercially available ion chambers in RT, all with different design characteristics, and use this information to produce a prototype ion chamber with improved performance in UHDR conditions as a first step toward ion chambers specific for FLASH-RT. The Advanced Markus and Exradin A10, A26, and A20 ion chambers were evaluated. The chambers were placed in a water tank, at a depth of 2 cm, and exposed to an UHDR electron beam at different pulse repetition frequency (PRF), pulse width (PW), and pulse amplitude settings on an IntraOp Mobetron. Ion chamber responses were investigated for the various beam parameter settings to isolate their dependence on integrated dose, mean dose rate and instantaneous dose rate, dose-per-pulse (DPP), and their design features such as chamber type, bias voltage, and collection volume. Furthermore, a thin parallel-plate (TPP) prototype ion chamber with reduced collector plate separation and volume was constructed and equally evaluated as the other chambers. The charge collection efficiency of the investigated ion chambers decreased with increasing DPP, whereas the mean dose rate did not affect the response of the chambers (± 1%). The dependence of the chamber response on DPP was found to be solely related to the total dose within the pulse, and not on mean dose rate, PW, or instantaneous dose rate within the ranges investigated. The polarity correction factor (Ppol ) values of the TPP prototype, A10, and Advanced Markus chambers were found to be independent of DPP and dose rate (± 2%), while the A20 and A26 chambers yielded significantly larger variations and dependencies under the same conditions. Ion chamber performance evaluated under different irradiation conditions of an UHDR electron beam revealed a strong dependence on DPP and a negligible dependence on the mean and instantaneous dose rates. These results suggest that modifications to ion chambers design to improve their usability in UHDR beamlines should focus on minimizing DPP effects, with emphasis on optimizing the electric field strength, through the construction of smaller electrode separation and larger bias voltages. This was confirmed through the production and evaluation of a prototype ion chamber specifically designed with these characteristics.
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Affiliation(s)
- Kevin Liu
- Division of Radiation Oncology, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- Graduate School of Biomedical Sciences, The University of Texas, Houston, Texas, USA
| | | | | | - Emil Schüler
- Division of Radiation Oncology, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- Graduate School of Biomedical Sciences, The University of Texas, Houston, Texas, USA
| | - Sam Beddar
- Division of Radiation Oncology, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- Graduate School of Biomedical Sciences, The University of Texas, Houston, Texas, USA
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15
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Dal Bello R, von der Grün J, Fabiano S, Rudolf T, Saltybaeva N, Stark LS, Ahmed M, Bathula M, Kucuker Dogan S, McNeur J, Guckenberger M, Tanadini-Lang S. Enabling ultra-high dose rate electron beams at a clinical linear accelerator for isocentric treatments. Radiother Oncol 2023; 187:109822. [PMID: 37516362 DOI: 10.1016/j.radonc.2023.109822] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 06/20/2023] [Accepted: 07/17/2023] [Indexed: 07/31/2023]
Abstract
BACKGROUND AND PURPOSE Radiotherapy delivery with ultra-high dose rates (UHDR) has consistently produced normal tissue sparing while maintaining efficacy for tumour control in preclinical studies, known as the FLASH effect. Modified clinical electron linacs have been used for pre-clinical studies at reduced source-surface distance (SSD) and novel intra-operative devices are becoming available. In this context, we modified a clinical linac to deliver 16 MeV UHDR electron beams with an isocentric setup. MATERIALS AND METHODS The first Varian TrueBeam (SN 1001) was clinically operative between 2009-2022, it was then decommissioned and converted into a research platform. The 18 MeV electron beam was converted into the experimental 16 MeV UHDR. Modifications were performed by Varian and included a software patch, thinner scattering foil and beam tuning. The dose rate, beam characteristics and reproducibility were measured with electron applicators at SSD = 100 cm. RESULTS The dose per pulse at isocenter was up to 1.28 Gy/pulse, corresponding to average and instantaneous dose rates up to 256 Gy/s and 3⋅105 Gy/s, respectively. Beam characteristics were equivalent between 16 MeV UHDR and conventional for field sizes up to 10x10cm2 and an overall beam reproducibility within ± 2.5% was measured. CONCLUSIONS We report on the first technical conversion of a Varian TrueBeam to produce 16 MeV UHDR electron beams. This research platform will allow isocenter experiments and deliveries with conventional setups up to field sizes of 10x10 cm2 within a hospital environment, reducing the gap between preclinical and clinical electron FLASH investigations.
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Affiliation(s)
- Riccardo Dal Bello
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland.
| | - Jens von der Grün
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Silvia Fabiano
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Thomas Rudolf
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Natalia Saltybaeva
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Luisa S Stark
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Md Ahmed
- Varian Medical Systems a Siemens Healthineers Company, Palo Alto, CA, USA
| | - Manohar Bathula
- Varian Medical Systems a Siemens Healthineers Company, Palo Alto, CA, USA
| | | | - Joshua McNeur
- Varian Medical Systems a Siemens Healthineers Company, Palo Alto, CA, USA
| | - Matthias Guckenberger
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Stephanie Tanadini-Lang
- Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
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16
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Jain S, Cetnar A, Woollard J, Gupta N, Blakaj D, Chakravarti A, Ayan AS. Pulse parameter optimizer: an efficient tool for achieving prescribed dose and dose rate with electron FLASH platforms. Phys Med Biol 2023; 68:19NT01. [PMID: 37735967 DOI: 10.1088/1361-6560/acf63e] [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: 04/24/2023] [Accepted: 09/01/2023] [Indexed: 09/23/2023]
Abstract
Purpose. Commercial electron FLASH platforms deliver ultra-high dose rate doses at discrete combinations of pulse parameters including pulse width (PW), pulse repetition frequency (PRF) and number of pulses (N), which dictate unique combinations of dose and dose rates. Additionally, collimation, source to surface distance, and airgaps also vary the dose per pulse (DPP). Currently, obtaining pulse parameters for the desired dose and dose rate is a cumbersome manual process involving creating, updating, and looking up values in large spreadsheets for every treatment configuration. This work presents a pulse parameter optimizer application to match intended dose and dose rate precisely and efficiently.Methods. Dose and dose rate calculation methods have been described for a commercial electron FLASH platform. A constrained optimization for the dose and dose rate cost function was modelled as a mixed integer problem in MATLAB (The MathWorks Inc., Version9.13.0 R2022b, Natick, Massachusetts). The beam and machine data required for the application were acquired using GafChromic film and alternating current current transformers (ACCTs). Variables for optimization included DPP for every collimator, PW and PRF measured using ACCT and airgap factors.Results. Using PW, PRF,Nand airgap factors as parameters, a software was created to optimize dose and dose rate, reaching the closest match if exact dose and dose rates are not achievable. Optimization took 20 s or less to converge to results. This software was validated for accuracy of dose calculation and precision in matching prescribed dose and dose rate.Conclusion. A pulse parameter optimization application was built for a commercial electron FLASH platform to increase efficiency in dose, dose rate, and pulse parameter prescription process. Automating this process reduces safety concerns associated with manual look up and calculation of these parameters, especially when many subjects at different doses and dose rates are to be safely managed.
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Affiliation(s)
- S Jain
- The Department of Radiation Oncology, The Ohio State University Wexner Medical Center, United States of America
| | - A Cetnar
- The Department of Radiation Oncology, The Ohio State University Wexner Medical Center, United States of America
| | - J Woollard
- The Department of Radiation Oncology, The Ohio State University Wexner Medical Center, United States of America
| | - N Gupta
- The Department of Radiation Oncology, The Ohio State University Wexner Medical Center, United States of America
| | - D Blakaj
- The Department of Radiation Oncology, The Ohio State University Wexner Medical Center, United States of America
| | - A Chakravarti
- The Department of Radiation Oncology, The Ohio State University Wexner Medical Center, United States of America
| | - A S Ayan
- The Department of Radiation Oncology, The Ohio State University Wexner Medical Center, United States of America
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Marinelli M, di Martino F, Del Sarto D, Pensavalle JH, Felici G, Giunti L, De Liso V, Kranzer R, Verona C, Verona Rinati G. A diamond detector based dosimetric system for instantaneous dose rate measurements in FLASH electron beams. Phys Med Biol 2023; 68:175011. [PMID: 37494946 DOI: 10.1088/1361-6560/acead0] [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: 05/10/2023] [Accepted: 07/25/2023] [Indexed: 07/28/2023]
Abstract
Objective.A reliable determination of the instantaneous dose rate (I-DR) delivered in FLASH radiotherapy treatments is believed to be crucial to assess the so-called FLASH effect in preclinical and biological studies. At present, no detectors nor real-time procedures are available to do that in ultra high dose rate (UH-DR) electron beams, typically consisting ofμs pulses characterized by I-DRs of the order of MGy/s. A dosimetric system is proposed possibly overcoming the above reported limitation, based on the recently developed flashDiamond (fD) detector (model 60025, PTW-Freiburg, Germany).Approach.A dosimetric system is proposed, based on a flashDiamond detector prototype, properly modified and adapted for very fast signal transmission. It was used in combination with a fast transimpedance amplifier and a digital oscilloscope to record the temporal traces of the pulses delivered by an ElectronFlash linac (SIT S.p.A., Italy). The proposed dosimetric systems was investigated in terms of the temporal characteristics of its response and the capability to measure the absolute delivered dose and instantaneous dose rate (I-DR). A 'standard' flashDiamond was also investigated and its response compared with the one of the specifically designed prototype.Main results. Temporal traces recorded in several UH-DR irradiation conditions showed very good signal to noise ratios and rise and decay times of the order of a few tens ns, faster than the ones obtained by the current transformer embedded in the linac head. By analyzing such signals, a calibration coefficient was derived for the fD prototype and found to be in agreement within 1% with the one obtained under reference60Co irradiation. I-DRs as high as about 2 MGy s-1were detected without any undesired saturation effect. Absolute dose per pulse values extracted by integrating the I-DR signals were found to be linear up to at least 7.13 Gy and in very good agreement with the ones obtained by connecting the fD to a UNIDOS electrometer (PTW-Freiburg, Germany). A good short term reproducibility of the linac output was observed, characterized by a pulse-to-pulse variation coefficient of 0.9%. Negligible differences were observed when replacing the fD prototype with a standard one, with the only exception of a somewhat slower response time for the latter detector type.Significance.The proposed fD-based system was demonstrated to be a suitable tool for a thorough characterization of UH-DR beams, providing accurate and reliable time resolved I-DR measurements from which absolute dose values can be straightforwardly derived.
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Affiliation(s)
- Marco Marinelli
- Dipartimento di Ingegneria Industriale, Università di Roma Tor Vergata, Roma, Italy
| | - Fabio di Martino
- U.O.Fisica Sanitaria, Azienda Universitaria Ospedaliera Pisana, Pisa, Italy
| | - Damiano Del Sarto
- U.O.Fisica Sanitaria, Azienda Universitaria Ospedaliera Pisana, Pisa, Italy
| | | | | | | | | | - Rafael Kranzer
- PTW-Freiburg, Freiburg D-79115, Germany
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University Oldenburg, D-26121 Germany
| | - Claudio Verona
- Dipartimento di Ingegneria Industriale, Università di Roma Tor Vergata, Roma, Italy
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18
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Froidevaux P, Grilj V, Bailat C, Geyer WR, Bochud F, Vozenin MC. FLASH irradiation does not induce lipid peroxidation in lipids micelles and liposomes. Radiat Phys Chem Oxf Engl 1993 2023. [DOI: 10.1016/j.radphyschem.2022.110733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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19
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Liu K, Palmiero A, Chopra N, Velasquez B, Li Z, Beddar S, Schüler E. Dual beam-current transformer design for monitoring and reporting of electron ultra-high dose rate (FLASH) beam parameters. J Appl Clin Med Phys 2023; 24:e13891. [PMID: 36601691 PMCID: PMC9924113 DOI: 10.1002/acm2.13891] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 12/12/2022] [Accepted: 12/15/2022] [Indexed: 01/06/2023] Open
Abstract
PURPOSE To investigate the usefulness and effectiveness of a dual beam-current transformer (BCTs) design to monitor and record the beam dosimetry output and energy of pulsed electron FLASH (eFLASH) beams in real-time, and to inform on the usefulness of this design for future eFLASH beam control. METHODS Two BCTs are integrated into the head of a FLASH Mobetron system, one located after the primary scattering foil and the other downstream of the secondary scattering foil. The response of the BCTs was evaluated individually to monitor beam output as a function of dose, scattering conditions, and ability to capture physical beam parameters such as pulse width (PW), pulse repetition frequency (PRF), and dose per pulse (DPP), and in combination to determine beam energy using the ratio of the lower-to-upper BCT signal. RESULTS A linear relationship was observed between the absorbed dose measured on Gafchromic film and the BCT signals for both the upper and lower BCT (R2 > 0.99). A linear relationship was also observed in the BCT signals as a function of the number of pulses delivered regardless of the PW, DPP, or PRF (R2 > 0.99). The lower-to-upper BCT ratio was found to correlate strongly with the energy of the eFLASH beam due to differential beam attenuation caused by the secondary scattering foil. The BCTs were also able to provide accurate information about the PW, PRF, energy, and DPP for each individual pulse delivered in real-time. CONCLUSION The dual BCT system integrated within the FLASH Mobetron was shown to be a reliable monitoring system able to quantify accelerator performance and capture all essential physical beam parameters on a pulse-by-pulse basis, and the ratio between the two BCTs was strongly correlated with beam energy. The fast signal readout and processing enables the BCTs to provide real-time information on beam output and energy and is proposed as a system suitable for accurate beam monitoring and control of eFLASH beams.
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Affiliation(s)
- Kevin Liu
- Department of Radiation PhysicsDivision of Radiation OncologyThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA,Graduate School of Biomedical SciencesThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA
| | - Allison Palmiero
- Department of Radiation PhysicsDivision of Radiation OncologyThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA
| | - Nitish Chopra
- Department of Radiation PhysicsDivision of Radiation OncologyThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA
| | - Brett Velasquez
- Department of Radiation PhysicsDivision of Radiation OncologyThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA
| | - Ziyi Li
- Department of BiostatisticsDivision of Basic SciencesThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA
| | - Sam Beddar
- Department of Radiation PhysicsDivision of Radiation OncologyThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA,Graduate School of Biomedical SciencesThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA
| | - Emil Schüler
- Department of Radiation PhysicsDivision of Radiation OncologyThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA,Graduate School of Biomedical SciencesThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA
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20
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Gao Y, Liu R, Chang C, Charyyev S, Zhou J, Bradley JD, Liu T, Yang X. A potential revolution in cancer treatment: A topical review of FLASH radiotherapy. J Appl Clin Med Phys 2022; 23:e13790. [PMID: 36168677 PMCID: PMC9588273 DOI: 10.1002/acm2.13790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Revised: 07/08/2022] [Accepted: 09/01/2022] [Indexed: 11/26/2022] Open
Abstract
FLASH radiotherapy (RT) is a novel technique in which the ultrahigh dose rate (UHDR) (≥40 Gy/s) is delivered to the entire treatment volume. Recent outcomes of in vivo studies show that the UHDR RT has the potential to spare normal tissue without sacrificing tumor control. There is a growing interest in the application of FLASH RT, and the ultrahigh dose irradiation delivery has been achieved by a few experimental and modified linear accelerators. The underlying mechanism of FLASH effect is yet to be fully understood, but the oxygen depletion in normal tissue providing extra protection during FLASH irradiation is a hypothesis that attracts most attention currently. Monte Carlo simulation is playing an important role in FLASH, enabling the understanding of its dosimetry calculations and hardware design. More advanced Monte Carlo simulation tools are under development to fulfill the challenge of reproducing the radiolysis and radiobiology processes in FLASH irradiation. FLASH RT may become one of standard treatment modalities for tumor treatment in the future. This paper presents the history and status of FLASH RT studies with a focus on FLASH irradiation delivery modalities, underlying mechanism of FLASH effect, in vivo and vitro experiments, and simulation studies. Existing challenges and prospects of this novel technique are discussed in this manuscript.
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Affiliation(s)
- Yuan Gao
- Department of Radiation Oncology and Winship Cancer InstituteEmory UniversityAtlantaGeorgiaUSA
| | - Ruirui Liu
- Department of Radiation Oncology and Winship Cancer InstituteEmory UniversityAtlantaGeorgiaUSA
| | - Chih‐Wei Chang
- Department of Radiation Oncology and Winship Cancer InstituteEmory UniversityAtlantaGeorgiaUSA
| | - Serdar Charyyev
- Department of Radiation Oncology and Winship Cancer InstituteEmory UniversityAtlantaGeorgiaUSA
| | - Jun Zhou
- Department of Radiation Oncology and Winship Cancer InstituteEmory UniversityAtlantaGeorgiaUSA
| | - Jeffrey D. Bradley
- Department of Radiation Oncology and Winship Cancer InstituteEmory UniversityAtlantaGeorgiaUSA
| | - Tian Liu
- Department of Radiation Oncology and Winship Cancer InstituteEmory UniversityAtlantaGeorgiaUSA
| | - Xiaofeng Yang
- Department of Radiation Oncology and Winship Cancer InstituteEmory UniversityAtlantaGeorgiaUSA
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21
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Poirier Y, Xu J, Mossahebi S, Therriault‐Proulx F, Sawant A. Technical note: Characterization and practical applications of a novel plastic scintillator for on‐line dosimetry for ultra‐high dose rate (FLASH). Med Phys 2022; 49:4682-4692. [DOI: 10.1002/mp.15671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 03/23/2022] [Accepted: 03/30/2022] [Indexed: 11/06/2022] Open
Affiliation(s)
- Yannick Poirier
- University of Maryland School of Medicine Baltimore MD 21201
- McGill University Montreal QC H3A 2T5 Canada
| | - Junliang Xu
- University of Maryland School of Medicine Baltimore MD 21201
| | - Sina Mossahebi
- University of Maryland School of Medicine Baltimore MD 21201
| | | | - Amit Sawant
- University of Maryland School of Medicine Baltimore MD 21201
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22
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Cavallone M, Jorge PG, Moeckli R, Bailat C, Flacco A, Prezado Y, Delorme R. Determination of the ion collection efficiency of the Razor Nano Chamber for ultra-high dose-rate electron beams. Med Phys 2022; 49:4731-4742. [PMID: 35441716 PMCID: PMC9539950 DOI: 10.1002/mp.15675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 04/07/2022] [Accepted: 04/12/2022] [Indexed: 11/10/2022] Open
Abstract
Background Ultra‐high dose‐rate (UHDR) irradiations (>40 Gy/s) have recently garnered interest in radiotherapy (RT) as they can trigger the so‐called “FLASH” effect, namely a higher tolerance of normal tissues in comparison with conventional dose rates when a sufficiently high dose is delivered to the tissue. To transfer this to clinical RT treatments, adapted methods and practical tools for online dosimetry need to be developed. Ionization chambers remain the gold standards in RT but the charge recombination effects may be very significant at such high dose rates, limiting the use of some of these dosimeters. The reduction of the sensitive volume size can be an interesting characteristic to reduce such effects. Purpose In that context, we have investigated the charge collection behavior of the recent IBA Razor™ Nano Chamber (RNC) in UHDR pulses to evaluate its potential interest for FLASH RT. Methods In order to quantify the RNC ion collection efficiency (ICE), simultaneous dose measurements were performed under UHDR electron beams with dose‐rate‐independent Gafchromic™ EBT3 films that were used as the dose reference. A dose‐per‐pulse range from 0.01 to 30 Gy was investigated, varying the source‐to‐surface distance, the pulse duration (1 and 3 μs investigated) and the LINAC gun grid tension as irradiation parameters. In addition, the RNC measurements were corrected from the inherent beam shot‐to‐shot variations using an independent current transformer. An empirical logistic model was used to fit the RNC collection efficiency measurements and the results were compared with the Advanced Markus plane parallel ion chamber. Results The RNC ICE was found to decrease as the dose‐per‐pulse increases, starting from doses above 0.2 Gy/pulse and down to 40% of efficiency at 30 Gy/pulse. The RNC resulted in a higher ICE for a given dose‐per‐pulse in comparison with the Markus chamber, with a measured efficiency found higher than 85 and 55% for 1 and 10 Gy/pulse, respectively, whereas the Markus ICE was of 60 and 25% for the same doses. However, the RNC shows a higher sensitivity to the pulse duration than the Advanced Markus chamber, with a lower efficiency found at 1 μs than at 3 μs, suggesting that this chamber could be more sensitive to the dose rate within the pulse. Conclusions The results confirmed that the small sensitive volume of the RNC ensures higher ICE compared with larger chambers. The RNC was thus found to be a promising online dosimetry tool for FLASH RT and we proposed an ion recombination model to correct its response up to extreme dose‐per‐pulses of 30 Gy.
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Affiliation(s)
- Marco Cavallone
- Institut Curie, PSL Research University, Radiation Oncology Department, Proton Therapy Centre, Centre Universitaire, Orsay, 91898, France.,Laboratoire d'Optique Appliquée, ENSTA Paris, École Polytechnique, CNRS-UMR7639, Institut Polytechnique de Paris, Palaiseau Cedex, 91762, France
| | | | - Raphaël Moeckli
- Institute of Radiation Physics, Lausanne University Hospital, Lausanne, Switzerland
| | - Claude Bailat
- Institute of Radiation Physics, Lausanne University Hospital, Lausanne, Switzerland
| | - Alessandro Flacco
- Laboratoire d'Optique Appliquée, ENSTA Paris, École Polytechnique, CNRS-UMR7639, Institut Polytechnique de Paris, Palaiseau Cedex, 91762, France
| | - Yolanda Prezado
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, Orsay, 91400, France.,Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, Orsay, 91400, France
| | - Rachel Delorme
- University of Grenoble Alpes, CNRS, Grenoble INP, LPSC-IN2P3, Grenoble, 38000, France.,Imagerie et Modélisation en Neurobiologie et Cancérologie (IMNC), CNRS Univ Paris-Sud, Université Paris-Saclay, Orsay, F-91400, France
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23
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Ashraf MR, Rahman M, Cao X, Duval K, Williams BB, Hoopes PJ, Gladstone DJ, Pogue BW, Zhang R, Bruza P. Individual pulse monitoring and dose control system for pre-clinical implementation of FLASH-RT. Phys Med Biol 2022; 67:10.1088/1361-6560/ac5f6f. [PMID: 35313290 PMCID: PMC10305796 DOI: 10.1088/1361-6560/ac5f6f] [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: 06/29/2021] [Accepted: 03/21/2022] [Indexed: 11/11/2022]
Abstract
Objective.Existing ultra-high dose rate (UHDR) electron sources lack dose rate independent dosimeters and a calibrated dose control system for accurate delivery. In this study, we aim to develop a custom single-pulse dose monitoring and a real-time dose-based control system for a FLASH enabled clinical linear accelerator (Linac).Approach.A commercially available point scintillator detector was coupled to a gated integrating amplifier and a real-time controller for dose monitoring and feedback control loop. The controller was programmed to integrate dose for each radiation pulse and stop the radiation beam when the prescribed dose was delivered. Additionally, the scintillator was mounted in a solid water phantom and placed underneath mice skin forin vivodose monitoring. The scintillator was characterized in terms of its radiation stability, mean dose-rate (Ḋm), and dose per pulse (Dp) dependence.Main results.TheDpexhibited a consistent ramp-up period across ∼4-5 pulse. The plastic scintillator was shown to be linear withḊm(40-380 Gy s-1) andDp(0.3-1.3 Gy Pulse-1) to within +/- 3%. However, the plastic scintillator was subject to significant radiation damage (16%/kGy) for the initial 1 kGy and would need to be calibrated frequently. Pulse-counting control was accurately implemented with one-to-one correspondence between the intended and the actual delivered pulses. The dose-based control was sufficient to gate on any pulse of the Linac.In vivodosimetry monitoring with a 1 cm circular cut-out revealed that during the ramp-up period, the averageDpwas ∼0.045 ± 0.004 Gy Pulse-1, whereas after the ramp-up it stabilized at 0.65 ± 0.01 Gy Pulse-1.Significance.The tools presented in this study can be used to determine the beam parameter space pertinent to the FLASH effect. Additionally, this study is the first instance of real-time dose-based control for a modified Linac at ultra-high dose rates, which provides insight into the tool required for future clinical translation of FLASH-RT.
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Affiliation(s)
- M. Ramish Ashraf
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
| | - Mahbubur Rahman
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
| | - Xu Cao
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
| | - Kayla Duval
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
| | - Benjamin B. Williams
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
| | - P. Jack Hoopes
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
- Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover NH 03755 USA
| | - David J. Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
| | - Brian W. Pogue
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
- Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover NH 03755 USA
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
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24
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Gonçalves Jorge P, Grilj V, Bourhis J, Vozenin M, Germond J, Bochud F, Bailat C, Moeckli R. Technical note: Validation of an ultrahigh dose rate pulsed electron beam monitoring system using a current transformer for FLASH preclinical studies. Med Phys 2022; 49:1831-1838. [PMID: 35066878 PMCID: PMC9303205 DOI: 10.1002/mp.15474] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 12/20/2021] [Accepted: 01/07/2021] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The Oriatron eRT6 is a linear accelerator (linac) used in FLASH preclinical studies able to reach dose rates ranging from conventional (CONV) up to ultrahigh (UHDR). This work describes the implementation of commercially available beam current transformers (BCTs) as online monitoring tools compatible with CONV and UHDR irradiations for preclinical FLASH studies. METHODS Two BCTs were used to measure the output of the Oriatron eRT6 linac. First, the correspondence between the set nominal beam parameters and those measured by the BCTs was checked. Then, we established the relationship between the total exit charge (measured by BCTs) and the absorbed dose to water. The influence of the pulse width (PW) and the pulse repetition frequency (PRF) at UHDR was characterized, as well as the short- and long-term stabilities of the relationship between the exit charge and the dose at CONV and UHDR. RESULTS The BCTs were able to determine consistently the number of pulses, PW, and PRF. For fixed PW and pulse height, the exit charge measured from BCTs was correlated with the dose, and linear relationships were found with uncertainties of 0.5 % and 3 % in CONV and UHDR mode, respectively. Short- and long-term stabilities of the dose-to-charge ratio were below 1.6 %. CONCLUSIONS We implemented commercially available BCTs and demonstrated their ability to act as online beam monitoring systems to support FLASH preclinical studies with CONV and UHDR irradiations. The implemented BCTs support dosimetric measurements, highlight variations among multiple measurements in a row, enable monitoring of the physics parameters used for irradiation, and are an important step for the safety of the clinical translation of FLASH radiation therapy.
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Affiliation(s)
- Patrik Gonçalves Jorge
- Institute of Radiation PhysicsLausanne University Hospital and University of LausanneLausanneSwitzerland
| | - Veljko Grilj
- Institute of Radiation PhysicsLausanne University Hospital and University of LausanneLausanneSwitzerland
| | - Jean Bourhis
- Radiation‐Oncology DepartmentLausanne University Hospital and University of LausanneLausanneSwitzerland
| | - Marie‐Catherine Vozenin
- Radiation‐Oncology LaboratoryLausanne University Hospital and University of LausanneLausanneSwitzerland
| | - Jean‐François Germond
- Institute of Radiation PhysicsLausanne University Hospital and University of LausanneLausanneSwitzerland
| | - François Bochud
- Institute of Radiation PhysicsLausanne University Hospital and University of LausanneLausanneSwitzerland
| | - Claude Bailat
- Institute of Radiation PhysicsLausanne University Hospital and University of LausanneLausanneSwitzerland
| | - Raphaël Moeckli
- Institute of Radiation PhysicsLausanne University Hospital and University of LausanneLausanneSwitzerland
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25
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Oesterle R, Gonçalves Jorge P, Grilj V, Bourhis J, Vozenin M, Germond J, Bochud F, Bailat C, Moeckli R. Implementation and validation of a beam-current transformer on a medical pulsed electron beam LINAC for FLASH-RT beam monitoring. J Appl Clin Med Phys 2021; 22:165-171. [PMID: 34609051 PMCID: PMC8598141 DOI: 10.1002/acm2.13433] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 08/28/2021] [Accepted: 09/13/2021] [Indexed: 12/18/2022] Open
Abstract
PURPOSE To implement and validate a beam current transformer as a passive monitoring device on a pulsed electron beam medical linear accelerator (LINAC) for ultra-high dose rate (UHDR) irradiations in the operational range of at least 3 Gy to improve dosimetric procedures currently in use for FLASH radiotherapy (FLASH-RT) studies. METHODS Two beam current transformers (BCTs) were placed at the exit of a medical LINAC capable of UHDR irradiations. The BCTs were validated as monitoring devices by verifying beam parameters consistency between nominal values and measured values, determining the relationship between the charge measured and the absorbed dose, and checking the short- and long-term stability of the charge-absorbed dose ratio. RESULTS The beam parameters measured by the BCTs coincide with the nominal values. The charge-dose relationship was found to be linear and independent of pulse width and frequency. Short- and long-term stabilities were measured to be within acceptable limits. CONCLUSIONS The BCTs were implemented and validated on a pulsed electron beam medical LINAC, thus improving current dosimetric procedures and allowing for a more complete analysis of beam characteristics. BCTs were shown to be a valid method for beam monitoring for UHDR (and therefore FLASH) experiments.
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Affiliation(s)
- Roxane Oesterle
- Institute of Radiation PhysicsLausanne University Hospital and Lausanne UniversityLausanneSwitzerland
| | - Patrik Gonçalves Jorge
- Institute of Radiation PhysicsLausanne University Hospital and Lausanne UniversityLausanneSwitzerland
| | - Veljko Grilj
- Institute of Radiation PhysicsLausanne University Hospital and Lausanne UniversityLausanneSwitzerland
| | - Jean Bourhis
- Radiation Oncology DepartmentLausanne University Hospital and Lausanne UniversityLausanneSwitzerland
| | - Marie‐Catherine Vozenin
- Radiation Oncology DepartmentLausanne University Hospital and Lausanne UniversityLausanneSwitzerland
| | - Jean‐François Germond
- Institute of Radiation PhysicsLausanne University Hospital and Lausanne UniversityLausanneSwitzerland
| | - François Bochud
- Institute of Radiation PhysicsLausanne University Hospital and Lausanne UniversityLausanneSwitzerland
| | - Claude Bailat
- Institute of Radiation PhysicsLausanne University Hospital and Lausanne UniversityLausanneSwitzerland
| | - Raphaël Moeckli
- Institute of Radiation PhysicsLausanne University Hospital and Lausanne UniversityLausanneSwitzerland
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