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Præstegaard LH. Radiation safety of ultra-high dose rate electron accelerators for FLASH radiotherapy. Med Phys 2024; 51:6206-6219. [PMID: 38941539 DOI: 10.1002/mp.17245] [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: 02/26/2024] [Revised: 05/16/2024] [Accepted: 05/22/2024] [Indexed: 06/30/2024] Open
Abstract
BACKGROUND An ultra-high dose rate (UHDR) electron accelerator for FLASH radiotherapy (RT) produces very intense bremsstrahlung by the interaction of the electron beam with objects both inside and outside of the accelerator. The bremsstrahlung dose per pulse is typically 1-2 orders of magnitude larger than that of conventional RT x-ray treatment of the same energy, and for electron energies above 10 MeV, the bremsstrahlung produces substantially more induced radioactivity outside the accelerator than for conventional RT. Therefore, a thorough radiation safety assessment is mandatory prior to the operation of a UHDR electron accelerator. PURPOSE To evaluate the radiation safety of a prototype FLASH-enabled Varian TrueBeam accelerator and to develop a general framework for assessment of all key radiation safety properties of a UHDR electron accelerator for FLASH RT. METHODS Production of bremsstrahlung and induced radioactivity by a UHDR electron accelerator is modeled by various analytical methods. The analytical modeling is compared with National Institute of Standards and Technology (NIST) bremsstrahlung yield data as well as measurements of primary bremsstrahlung outside the bunker and induced radioactivity of irradiated thick targets for a FLASH-enabled 16 MeV Varian TrueBeam electron accelerator. In addition, the analytical modeling is complemented by measurements of secondary bremsstrahlung inside/outside the bunker and neutrons at the maze entrance. RESULTS Calculated bremsstrahlung yields deviate maximum 8.5% from NIST data, and all measurements of primary bremsstrahlung and induced radioactivity agree with calculations, validating the analytical tools. In addition, it is found that scattering foil bremsstrahlung dominates primary bremsstrahlung and the main source of secondary bremsstrahlung is the irradiated object outside the accelerator. It follows that primary and secondary bremsstrahlung outside the bunker can be calculated using the same simple formalism as that used for conventional RT. Measured primary bremsstrahlung tenth-value layers for concrete of the simple formalism are in good agreement with NCRP and IAEA data, while measured secondary bremsstrahlung tenth-value layers for concrete are considerably lower than NCRP and IAEA data. All calculations and measurements form a general framework for assessment of all key radiation safety properties of a UHDR electron accelerator. CONCLUSIONS The FLASH-enabled Varian TrueBeam accelerator is safe for normal operation (max. 99 pulses per irradiation) in a bunker designed for at least 15 MV conventional x-ray treatment unless the UHDR workload is much larger than the x-ray workload. A similar finding applies to other UHDR electron accelerators. However, during beam tuning, radiation survey, or other tests with extended irradiation time, the UHDR workload may become very large, necessitating the implementation of additional safety measures.
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Mossahebi S, Byrne K, Jiang K, Gerry A, Deng W, Repetto C, Jackson IL, Sawant A, Poirier Y. A high-throughput focused collimator for OAR-sparing preclinical proton FLASH studies: commissioning and validation. Phys Med Biol 2024; 69:14NT01. [PMID: 38876112 DOI: 10.1088/1361-6560/ad589f] [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: 03/23/2024] [Accepted: 06/14/2024] [Indexed: 06/16/2024]
Abstract
Objective. To fabricate and validate a novel focused collimator designed to spare normal tissue in a murine hemithoracic irradiation model using 250 MeV protons delivered at ultra-high dose rates (UHDRs) for preclinical FLASH radiation therapy (FLASH-RT) studies.Approach. A brass collimator was developed to shape 250 MeV UHDR protons from our Varian ProBeam. Six 13 mm apertures, of equivalent size to kV x-ray fields historically used to perform hemithorax irradiations, were precisely machined to match beam divergence, allowing concurrent hemithoracic irradiation of six mice while sparing the contralateral lung and abdominal organs. The collimated field profiles were characterized by film dosimetry, and a radiation survey of neutron activation was performed to ensure the safety of staff positioning animals.Main results. The brass collimator produced 1.2 mm penumbrae radiation fields comparable to kV x-rays used in preclinical studies. The penumbrae in the six apertures are similar, with full-width half-maxima of 13.3 mm and 13.5 mm for the central and peripheral apertures, respectively. The collimator delivered a similar dose at an average rate of 52 Gy s-1for all apertures. While neutron activation produces a high (0.2 mSv h-1) initial ambient equivalent dose rate, a parallel work-flow in which imaging and setup are performed without the collimator ensures safety to staff.Significance. Scanned protons have the greatest potential for future translation of FLASH-RT in clinical treatments due to their ability to treat deep-seated tumors with high conformality. However, the Gaussian distribution of dose in proton spots produces wider lateral penumbrae compared to other modalities. This presents a challenge in small animal pre-clinical studies, where millimeter-scale penumbrae are required to precisely target the intended volume. Offering high-throughput irradiation of mice with sharp penumbrae, our novel collimator-based platform serves as an important benchmark for enabling large-scale, cost-effective radiobiological studies of the FLASH effect in murine models.
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Affiliation(s)
- Sina Mossahebi
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America
| | - Kevin Byrne
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America
| | - Kai Jiang
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America
| | - Andrew Gerry
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America
| | - Wei Deng
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America
| | - Carlo Repetto
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America
| | - Isabel L Jackson
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America
- True North Biopharm, LLC, Rockville, MD, United States of America
| | - Amit Sawant
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America
| | - Yannick Poirier
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America
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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] [MESH Headings] [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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Konradsson E, Ericsson Szecsenyi R, Wahlqvist P, Thoft A, Blad B, Bäck SÅ, Ceberg C, Petersson K. Reconfiguring a Plane-Parallel Transmission Ionization Chamber to Extend the Operating Range into the Ultra-High Dose-per-pulse Regime. Radiat Res 2024; 201:252-260. [PMID: 38308528 DOI: 10.1667/rade-23-00177.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 01/24/2024] [Indexed: 02/04/2024]
Abstract
This study aims to investigate the feasibility of enhancing the charge collection efficiency (CCE) of a transmission chamber by reconfiguring its design and operation. The goal was to extend the range of dose-per-pulse (DPP) values with no or minimal recombination effects up to the ultra-high dose rate (UHDR) regime. The response of two transmission chambers, with electrode distance of 1 mm and 0.6 mm, respectively, was investigated as a function of applied voltage. The chambers were mounted one-by-one in the electron applicator of a 10 MeV FLASH-modified clinical linear accelerator. The chamber signals were measured as a function of nominal DPP, which was determined at the depth of dose maximum using EBT-XD film in solid water and ranged from 0.6 mGy per pulse to 0.9 Gy per pulse, for both the standard voltage of 320 V and the highest possible safe voltage of 1,200 V. The CCE was calculated and fitted with an empirical logistic function that incorporated the electrode distance and the chamber voltage. The CCE decreased with increased DPP. The CCE at the highest achievable DPP was 24% (36%) at 320 V and 51% (82%) at 1,200 V, for chambers with 1 mm (0.6 mm) electrode distance. For the combination of 1,200 V- and 0.6-mm electrode distance, the CCE was ∼100% for average dose rate up to 70 Gy/s at the depth of dose maximum in the phantom at a source-to-surface distance of 100 cm. Our findings indicate that minor modifications to a plane-parallel transmission chamber can substantially enhance the CCE and extending the chamber's operating range to the UHDR regime. This supports the potential of using transmission chamber-based monitoring solutions for UHDR beams, which could facilitate the delivery of UHDR treatments using an approach similar to conventional clinical delivery.
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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 Åj 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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Byrne KE, Poirier Y, Xu J, Gerry A, Foley MJ, Jackson IL, Sawant A, Jiang K. Technical note: A small animal irradiation platform for investigating the dependence of the FLASH effect on electron beam parameters. Med Phys 2024; 51:1421-1432. [PMID: 38207016 DOI: 10.1002/mp.16909] [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: 06/27/2023] [Revised: 10/30/2023] [Accepted: 12/12/2023] [Indexed: 01/13/2024] Open
Abstract
BACKGROUND The recent rediscovery of the FLASH effect, a normal tissue sparing phenomenon observed in ultra-high dose rate (UHDR) irradiations, has instigated a surge of research endeavors aiming to close the gap between experimental observation and clinical treatment. However, the dependences of the FLASH effect and its underpinning mechanisms on beam parameters are not well known, and large-scale in vivo studies using murine models of human cancer are needed for these investigations. PURPOSE To commission a high-throughput, variable dose rate platform providing uniform electron fields (≥15 cm diameter) at conventional (CONV) and UHDRs for in vivo investigations of the FLASH effect and its dependences on pulsed electron beam parameters. METHODS A murine whole-thoracic lung irradiation (WTLI) platform was constructed using a 1.3 cm thick Cerrobend collimator forming a 15 × 1.6 cm2 slit. Control of dose and dose rate were realized by adjusting the number of monitor units and couch vertical position, respectively. Achievable doses and dose rates were investigated using Gafchromic EBT-XD film at 1 cm depth in solid water and lung-density phantoms. Percent depth dose (PDD) and dose profiles at CONV and various UHDRs were also measured at depths from 0 to 2 cm. A radiation survey was performed to assess radioactivation of the Cerrobend collimator by the UHDR electron beam in comparison to a precision-machined copper alternative. RESULTS This platform allows for the simultaneous thoracic irradiation of at least three mice. A linear relationship between dose and number of monitor units at a given UHDR was established to guide the selection of dose, and an inverse-square relationship between dose rate and source distance was established to guide the selection of dose rate between 20 and 120 Gy·s-1 . At depths of 0.5 to 1.5 cm, the depth range relevant to murine lung irradiation, measured PDDs varied within ±1.5%. Similar lateral dose profiles were observed at CONV and UHDRs with the dose penumbrae widening from 0.3 mm at 0 cm depth to 5.1 mm at 2.0 cm. The presence of lung-density plastic slabs had minimal effect on dose distributions as compared to measurements made with only solid water slabs. Instantaneous dose rate measurements of the activated copper collimator were up to two orders of magnitude higher than that of the Cerrobend collimator. CONCLUSIONS A high-throughput, variable dose rate platform has been developed and commissioned for murine WTLI electron FLASH radiotherapy. The wide field of our UHDR-enabled linac allows for the simultaneous WTLI of at least three mice, and for the average dose rate to be modified by changing the source distance, without affecting dose distribution. The platform exhibits uniform, and comparable dose distributions at CONV and UHDRs up to 120 Gy·s-1 , owing to matched and flattened 16 MeV CONV and UHDR electron beams. Considering radioactivation and exposure to staff, Cerrobend collimators are recommended above copper alternatives for electron FLASH research. This platform enables high-throughput animal irradiation, which is preferred for experiments using a large number of animals, which are required to effectively determine UHDR treatment efficacies.
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Affiliation(s)
- Kevin E Byrne
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
- Department of Physics, School of Natural Sciences, University of Galway, Galway, Ireland
| | - Yannick Poirier
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Junliang Xu
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Andrew Gerry
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Mark J Foley
- Department of Physics, School of Natural Sciences, University of Galway, Galway, Ireland
| | - Isabel Lauren Jackson
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Amit Sawant
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Kai Jiang
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
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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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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: 5] [Impact Index Per Article: 5.0] [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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Lang X, Hu Z, Zhao Z, Zhou K, Xu Z, Li M, Mao R, Luo F, Huang C, Kang X, Li J, Liu X, Zhou L, Xiao G. Preliminary study of low-pressure ionization chamber for online dose monitoring in FLASH carbon ion radiotherapy. Phys Med Biol 2024; 69:025008. [PMID: 38064745 DOI: 10.1088/1361-6560/ad13d0] [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: 07/26/2023] [Accepted: 12/08/2023] [Indexed: 01/09/2024]
Abstract
The FLASH effect of carbon ion therapy has recently attracted significant attention from the scientific community. However, the radiobiological mechanism of the effect and the exact therapeutic conditions are still under investigation. Therefore, the dosimetry accuracy is critical for testing hypotheses about the effect and quantifying FLASH Radiotherapy. In this paper, the FLASH ionization chamber at low-pressure was designed, and its dose rate dependence was verified with the Faraday cup. In addition, the dose response was tested under the air pressure of the ionization chamber of 10 mbar, 80 mbar and 845 mbar, respectively. The results showed that when the pressure was 10 mbar, the dose linearity was verified and calibrated at the dose rate of ∼50 Gy s-1, and the residuals were less than 2%. In conclusion, the FLASH ionization chamber is a promising instrument for online dose monitoring.
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Affiliation(s)
- Xinle Lang
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
- University of Chinese Academy of Sciences, School of Nuclear Science and Technology, Beijing 100049, People's Republic of China
| | - Zhengguo Hu
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
- University of Chinese Academy of Sciences, School of Nuclear Science and Technology, Beijing 100049, People's Republic of China
| | - Zulong Zhao
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
| | - Kai Zhou
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
| | - Zhiguo Xu
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
| | - Min Li
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
| | - Ruishi Mao
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
- University of Chinese Academy of Sciences, School of Nuclear Science and Technology, Beijing 100049, People's Republic of China
| | - Faming Luo
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
- University of Chinese Academy of Sciences, School of Nuclear Science and Technology, Beijing 100049, People's Republic of China
| | - Chuan Huang
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, Gansu, People's Republic of China
| | - Xincai Kang
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
| | - Juan Li
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
| | - Xiaotao Liu
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
| | - Libin Zhou
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
| | - Guoqing Xiao
- Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou 730000, Gansu, People's Republic of China
- University of Chinese Academy of Sciences, School of Nuclear Science and Technology, Beijing 100049, People's Republic of China
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No HJ, Wu YF, Dworkin ML, Manjappa R, Skinner L, Ashraf MR, Lau B, Melemenidis S, Viswanathan V, Yu ASJ, Surucu M, Schüler E, Graves EE, Maxim PG, Loo BW. Clinical Linear Accelerator-Based Electron FLASH: Pathway for Practical Translation to FLASH Clinical Trials. Int J Radiat Oncol Biol Phys 2023; 117:482-492. [PMID: 37105403 DOI: 10.1016/j.ijrobp.2023.04.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 03/03/2023] [Accepted: 04/11/2023] [Indexed: 04/29/2023]
Abstract
PURPOSE Ultrahigh-dose-rate (UHDR) radiation therapy (RT) has produced the FLASH effect in preclinical models: reduced toxicity with comparable tumor control compared with conventional-dose-rate RT. Early clinical trials focused on UHDR RT feasibility using specialized devices. We explore the technical feasibility of practical electron UHDR RT on a standard clinical linear accelerator (LINAC). METHODS AND MATERIALS We tuned the program board of a decommissioned electron energy for UHDR electron delivery on a clinical LINAC without hardware modification. Pulse delivery was controlled using the respiratory gating interface. A short source-to-surface distance (SSD) electron setup with a standard scattering foil was configured and tested on an anthropomorphic phantom using circular blocks with 3- to 20-cm field sizes. Dosimetry was evaluated using radiochromic film and an ion chamber profiler. RESULTS UHDR open-field mean dose rates at 100, 80, 70, and 59 cm SSD were 36.82, 59.52, 82.01, and 112.83 Gy/s, respectively. At 80 cm SSD, mean dose rate was ∼60 Gy/s for all collimated field sizes, with an R80 depth of 6.1 cm corresponding to an energy of 17.5 MeV. Heterogeneity was <5.0% with asymmetry of 2.2% to 6.2%. The short SSD setup was feasible under realistic treatment conditions simulating broad clinical indications on an anthropomorphic phantom. CONCLUSIONS Short SSD and tuning for high electron beam current on a standard clinical LINAC can deliver flat, homogenous UHDR electrons over a broad, clinically relevant range of field sizes and depths with practical working distances in a configuration easily reversible to standard clinical use.
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Affiliation(s)
- Hyunsoo Joshua No
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Yufan Fred Wu
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Michael Louis Dworkin
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Rakesh Manjappa
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Lawrie Skinner
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - M Ramish Ashraf
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Brianna Lau
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Stavros Melemenidis
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Vignesh Viswanathan
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Amy Shu-Jung Yu
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Murat Surucu
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Emil Schüler
- Department of Radiation Physics, Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Edward Elliot Graves
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California; Stanford Cancer Institute, Stanford University School of Medicine, Stanford, California
| | - Peter Gregor Maxim
- Department of Radiation Oncology, University of California, Irvine, Orange, California
| | - Billy W Loo
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California; Stanford Cancer Institute, Stanford University School of Medicine, Stanford, California.
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10
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Xiao Z, Zhang Y, Speth J, Lee E, Mascia A, Lamba M. Evaluation of a conventionally shielded proton treatment room for FLASH radiotherapy. Med Phys 2022; 49:6765-6773. [PMID: 36114793 PMCID: PMC10091931 DOI: 10.1002/mp.15964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 07/27/2022] [Accepted: 08/28/2022] [Indexed: 12/13/2022] Open
Abstract
PURPOSE FLASH radiotherapy (FLASH-RT) is the potential for a major breakthrough in cancer care, as preclinical results have shown significantly reduced toxicities to healthy tissues while maintaining excellent tumor control. However, FLASH conditions were not considered in the current proton facilities' shielding designs. The purpose of this study is to validate the adequacy of conventionally shielded proton rooms used for FLASH-RT. METHODS Clinical FLASH irradiations typically take place in a few 100 ms, orders of magnitude shorter than the response time of the wide-energy neutron detector (WENDI-II). The nozzle beam current (representing the dose rate) dependence of the WENDI-II detector response was empirically determined to stabilize with a beam current of ≤10 nA at the measurement point with the highest dose rate. A large, predefined proton transmission FLASH plan (250 MeV, 7 × 20 cm2 , 8 Gy at isocenter) was commissioned as part of a FLASH clinical trial. For purpose of this study, that field was adjusted from 250 to 244 MeV, allowing a lower beam current of 10 nA to provide reliable detector response. Radiation surveys were performed for the proton beams with/without extra beam stopper (30 × 30 × 40-cm3 solid water slabs) at 0°, 90°, 180°, and 270° gantry angles. RESULTS Ambient doses were recorded at seven different locations. A 170-nA beam current, commonly used for clinical FLASH plans, was chosen to normalize the average ambient dose rate to FLASH conditions. Assuming 200-Gy/h workload (25 FLASH beams, 8 Gy/beam), annual occupational dose at controlled areas was calculated. For all gantry angles, ≤0.4 mSv/year is expected at treatment room door. The highest ambient dose, 2.46 mSv/year, ∼5% of the maximum annual permissible occupational dose, was identified at the isocenter of the adjacent treatment room with 90° gantry. CONCLUSION These survey results indicate that our conventionally shielded proton rotating gantry rooms result in acceptable occupational and public doses when the transmission FLASH beams delivered at four cardinal gantry angles based on 200-Gy/h workload assumption. These findings support that FLASH clinical trials in our conventionally shielded proton facilities can be safely implemented.
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Affiliation(s)
- Zhiyan Xiao
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.,Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Yongbin Zhang
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.,Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Joseph Speth
- Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Eunsin Lee
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.,Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Anthony Mascia
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.,Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Michael Lamba
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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11
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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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12
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Perstin A, Poirier Y, Sawant A, Tambasco M. Quantifying the DNA-damaging effects of FLASH irradiation with plasmid DNA. Int J Radiat Oncol Biol Phys 2022; 113:437-447. [PMID: 35124135 DOI: 10.1016/j.ijrobp.2022.01.049] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 01/19/2022] [Accepted: 01/26/2022] [Indexed: 11/15/2022]
Abstract
PURPOSE To investigate a plasmid DNA nicking assay approach for isolating and quantifying the DNA damaging effects of ultra-high dose rate (i.e., FLASH) irradiation relative to conventional dose rate irradiation. METHODS We constructed and irradiated phantoms containing plasmid DNA to nominal doses of 20 Gy and 30 Gy using 16 MeV electrons at conventional (0.167 Gy/s) and FLASH (46.6 Gy/s and 93.2 Gy/s) dose rates. We delivered conventional dose rates using a standard clinical Varian iX linac and FLASH dose rates (FDR) using a modified Varian 21EX C-series linac. We ran the irradiated DNA and controls (0 Gy) through an agarose gel electrophoresis procedure that sorted and localized the DNA into bands associated with single strand breaks (SSBs), double strand breaks (DSBs), and undamaged DNA. We quantitatively analyzed the gel images to compute the relative yields of SSBs and DSBs, and applied a mathematical model of plasmid DNA damage as a function of dose to compute relative biological effectiveness (RBE) of SSB and DSB (RBESSBandRBEDSB) damage for a given endpoint and FDR. RESULTS Both RBESSBandRBEDSB were less than unity with the FDR irradiations, indicating FLASH sparing. With regard to the more deleterious DNA DSB damage, RBEDSBs of FLASH beams at dose rates of 46.6 Gy/s and 93.2 Gy/s relative to the conventional 16 MeV beam dose rate were 0.54 ± 0.15 and 0.55 ± 0.17, respectively. CONCLUSION We have demonstrated the feasibility of using a DNA-based phantom to isolate and assess the FLASH sparing effect on DNA. We also found that FLASH irradiation causes less damage to DNA compared to a conventional dose rate. This result supports the notion that the protective effect of FLASH irradiation occurs at least partially via fundamental biochemical processes.
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Affiliation(s)
- Alan Perstin
- Physics Graduate Student, San Diego State University
| | - Yannick Poirier
- Assistant Professor, Oncology, Department of Radiation Oncology, University of Maryland
| | - Amit Sawant
- Professor and Vice Chair, Department of Radiation Oncology, University of Maryland
| | - Mauro Tambasco
- Associate Professor/Medical Physicist, Associate Program Director, Medical Physics Residency, Associate Director, Medical Physics , Department of Physics, San Diego State University.
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13
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Guerrieri P, Jacob NK, Maxim PG, Sawant A, Van Nest SJ, Mohindra P, Dominello MM, Burmeister JW, Joiner MC. Three discipline collaborative radiation therapy (3DCRT) special debate: FLASH radiotherapy needs ongoing basic and animal research before implementing it to a large clinical scale. J Appl Clin Med Phys 2022; 23:e13547. [PMID: 35104025 PMCID: PMC8992943 DOI: 10.1002/acm2.13547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 01/20/2022] [Indexed: 11/15/2022] Open
Affiliation(s)
- Patrizia Guerrieri
- Department of Radiation Oncology, Bon Secours Mercy Health, Youngstown, Ohio, USA
| | | | - Peter G Maxim
- Department of Radiation Oncology, University of California, Irvine, California, USA
| | - Amit Sawant
- Department of Radiation Oncology, University of Maryland, Baltimore, Maryland, USA.,Maryland Proton Treatment Center, Baltimore, Maryland, USA
| | - Samantha J Van Nest
- Department of Radiation Oncology, Weill Cornell Medicine, New York, New York, USA
| | - Pranshu Mohindra
- Department of Radiation Oncology, University of Maryland, Baltimore, Maryland, USA.,Maryland Proton Treatment Center, Baltimore, Maryland, USA
| | | | - Jay W Burmeister
- Department of Oncology, Wayne State University, Detroit, Michigan, USA.,Gershenson Radiation Oncology Center, Barbara Ann Karmanos Cancer Institute, Detroit, Michigan, USA
| | - Michael C Joiner
- Department of Oncology, Wayne State University, Detroit, Michigan, USA
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