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Oh K, Gallagher KJ, Yan Y, Zhou S. Commissioning and initial validation of Eclipse eMC algorithm for the electron FLASH research extension (FLEX) system for pre-clinical studies. J Appl Clin Med Phys 2024; 25:e14289. [PMID: 38319666 PMCID: PMC11087161 DOI: 10.1002/acm2.14289] [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: 09/04/2023] [Revised: 12/13/2023] [Accepted: 01/22/2024] [Indexed: 02/07/2024] Open
Abstract
PURPOSE To investigate the feasibility of commissioning the 16 MeV electron FLASH Extension (FLEX) in the commercial treatment planning system (TPS) for biomedical research with cell and mouse models, and in silico treatment planning studies. METHODS To commission the FLEX system with the electron Monte Carlo (eMC) algorithm in the commercial TPS, radiochromic film was used to measure the vendor-recommended beam data. Once the beam model was generated for the eMC algorithm, supplemental measurements were collected for validation purposes and compared against the TPS-calculated results. Additionally, the newly commissioned 16 MeV FLASH beam was compared to the corresponding 16 MeV conventional electron beam. RESULTS The eMC algorithm effectively modeled the FLEX system. The eMC-calculated PDDs and profiles for the 16 MeV electron FLASH beam agreed with measured values within 1%, on average, for 6 × 6 cm2 and 10 × 10 cm2 applicators. Flatness and symmetry deviated by less than 1%, while FWHM and penumbra agreed within 1 mm for both eMC-calculated and measured profiles. Additionally, the small field (i.e., 2-cm diameter cutout) that was measured for validation purposes agreed with TPS-calculated results within 1%, on average, for both the PDD and profiles. The FLASH and conventional dose rate 16 MeV electron beam were in agreement in regard to energy, but the profiles for larger field sizes began to deviate (>10 × 10 cm2) due to the forward-peaked nature of the FLASH beam. For cell irradiation experiments, the measured and eMC-calculated in-plane and cross-plane absolute dose profiles agreed within 1%, on average. CONCLUSIONS The FLEX system was successfully commissioned in the commercial TPS using the eMC algorithm, which accurately modeled the forward-peaked nature of the FLASH beam. A commissioned TPS for FLASH will be useful for pre-clinical cell and animal studies, as well as in silico FLASH treatment planning studies for future clinical implementation.
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Affiliation(s)
- Kyuhak Oh
- Department of Radiation OncologyUniversity of Nebraska Medical CenterOmahaNebraskaUSA
| | - Kyle J. Gallagher
- Department of Radiation OncologyUniversity of Nebraska Medical CenterOmahaNebraskaUSA
| | - Ying Yan
- Department of Radiation OncologyUniversity of Nebraska Medical CenterOmahaNebraskaUSA
| | - Sumin Zhou
- Department of Radiation OncologyUniversity of Nebraska Medical CenterOmahaNebraskaUSA
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Tang R, Yin J, Liu Y, Xue J. FLASH radiotherapy: A new milestone in the field of cancer radiotherapy. Cancer Lett 2024; 587:216651. [PMID: 38342233 DOI: 10.1016/j.canlet.2024.216651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 11/03/2023] [Accepted: 01/13/2024] [Indexed: 02/13/2024]
Abstract
Radiotherapy plays a pivotal role in the control and eradication of tumors, but it can also induce radiation injury to surrounding normal tissues while targeting tumor cells. In recent years, FLASH-Radiotherapy (FLASH-RT) has emerged as a cutting-edge research focus in the field of radiation therapy. By delivering high radiation doses to the treatment target in an ultra-short time, FLASH-RT produces the FLASH effect, which reduces the toxicity to normal tissues while achieving comparable tumor control efficacy to conventional radiotherapy. This review provides a brief overview of the development history of FLASH-RT and its impact on tumor control. Additionally, it focuses on introducing the protective effects and molecular mechanisms of this technology on various normal tissues, as well as exploring its synergistic effects when combined with other tumor therapies. Importantly, this review discusses the challenges faced in translating FLASH-RT into clinical practice and outlines its promising future applications.
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Affiliation(s)
- Rui Tang
- Hospital of Chengdu University of Traditional Chinese Medicine, Chengdu, 610072, Sichuan, China; Division of Thoracic Tumor Multimodality Treatment, Cancer Center, The National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Jianqiong Yin
- Division of Thoracic Tumor Multimodality Treatment, Cancer Center, The National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Yuanxin Liu
- Division of Thoracic Tumor Multimodality Treatment, Cancer Center, The National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Jianxin Xue
- Division of Thoracic Tumor Multimodality Treatment, Cancer Center, The National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China; Department of Radiation Oncology, Cancer Center, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China; Laboratory of Clinical Cell Therapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China; Disaster Medical Center, Sichuan University, Chengdu, 610041, Sichuan, China.
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Spruijt K, Mossahebi S, Lin H, Lee E, Kraus J, Dhabaan A, Poulsen P, Lowe M, Ayan A, Spiessens S, Godart J, Hoogeman M. Multi-institutional consensus on machine QA for isochronous cyclotron-based systems delivering ultra-high dose rate (FLASH) pencil beam scanning proton therapy in transmission mode. Med Phys 2024; 51:786-798. [PMID: 38103260 DOI: 10.1002/mp.16854] [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: 04/23/2023] [Revised: 10/07/2023] [Accepted: 10/31/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND The first clinical trials to assess the feasibility of FLASH radiotherapy in humans have started (FAST-01, FAST-02) and more trials are foreseen. To increase comparability between trials it is important to assure treatment quality and therefore establish a standard for machine quality assurance (QA). Currently, the AAPM TG-224 report is considered as the standard on machine QA for proton therapy, however, it was not intended to be used for ultra-high dose rate (UHDR) proton beams, which have gained interest due to the observation of the FLASH effect. PURPOSE The aim of this study is to find consensus on practical guidelines on machine QA for UHDR proton beams in transmission mode in terms of which QA is required, how they should be done, which detectors are suitable for UHDR machine QA, and what tolerance limits should be applied. METHODS A risk assessment to determine the gaps in the current standard for machine QA was performed by an international group of medical physicists. Based on that, practical guidelines on how to perform machine QA for UHDR proton beams were proposed. RESULTS The risk assessment clearly identified the need for additional guidance on temporal dosimetry, addressing dose rate (constancy), dose spillage, and scanning speed. In addition, several minor changes from AAPM TG-224 were identified; define required dose rate levels, the use of clinically relevant dose levels, and the use of adapted beam settings to minimize activation of detector and phantom materials or to avoid saturation effects of specific detectors. The final report was created based on discussions and consensus. CONCLUSIONS Consensus was reached on what QA is required for UHDR scanning proton beams in transmission mode for isochronous cyclotron-based systems and how they should be performed. However, the group discussions also showed that there is a lack of high temporal resolution detectors and sufficient QA data to set appropriate limits for some of the proposed QA procedures.
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Affiliation(s)
- Kees Spruijt
- HollandPTC, Delft, The Netherlands
- Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Sina Mossahebi
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Haibo Lin
- New York Proton Center, New York, New York, USA
| | - Eunsin Lee
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, Ohio, USA
| | - James Kraus
- Department of Radiation Oncology, University of Alabama-Birmingham, Birmingham, Alabama, USA
| | - Anees Dhabaan
- Department of Radiation Oncology, Emory University of Medicine, Atlanta, Georgia, USA
| | - Per Poulsen
- Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark and Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Matthew Lowe
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK
| | - Ahmet Ayan
- Department of Radiation Oncology, Ohio State University Medical Center, Columbus, Ohio, USA
| | - Sylvie Spiessens
- Varian, a Siemens Healthineers Company, Groot-Bijgaarden, Belgium
| | - Jeremy Godart
- HollandPTC, Delft, The Netherlands
- Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Mischa Hoogeman
- HollandPTC, Delft, The Netherlands
- Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Mascia A, McCauley S, Speth J, Nunez SA, Boivin G, Vilalta M, Sharma RA, Perentesis JP, Sertorio M. Impact of Multiple Beams on the FLASH Effect in Soft Tissue and Skin in Mice. Int J Radiat Oncol Biol Phys 2024; 118:253-261. [PMID: 37541394 DOI: 10.1016/j.ijrobp.2023.07.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 06/19/2023] [Accepted: 07/14/2023] [Indexed: 08/06/2023]
Abstract
PURPOSE FLASH proton pencil beam scanning (p-PBS) showed a reduction in mouse skin toxicity and fibrosis when delivered as a single, uninterrupted, high-dose fraction. Clinical p-PBS treatment usually requires multiple beams to achieve good conformality, and these beams are separated by minutes to allow patient and equipment repositioning. We evaluate the impact of multibeam versus single-beam proton radiation on the FLASH sparing effect on skin toxicity. METHODS AND MATERIALS The right hind leg of 10-week-old female C57Bl/6j mice was irradiated using a Varian ProBeam proton beam scanning gantry system at conventional (1 Gy/s) or FLASH (100 Gy/s) average field dose rate. We scored the skin toxicity after different doses for 7 weeks. The treatment was delivered as 1, 2, or 3 equal beams with an interruption of 2 minutes. For each beam delivery, the equipment remained in the same position so that there was a full overlap of beams administered. RESULTS Single-beam delivery confirmed a benefit for p-PBS FLASH in this model at 30, 35, and 40 Gy. At 30 and 35 Gy, a single beam interruption of 2 minutes (2 × 15 Gy or 2 × 17.5 Gy) reduced the FLASH sparing effect, which remained significant (P < .001). However, 2 interruptions (3 × 10 Gy or 3 × 11.6 Gy) abrogated the normal tissue sparing effect. CONCLUSIONS Our results indicate that the FLASH sparing effect in areas of beam overlap can be compromised by interruptions in delivery time. Time gap between overlapping beams and spatial arrangement of the delivered beams are important parameters for FLASH studies. The effect of multibeam needs to be studied on different organs of interest.
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Affiliation(s)
- Anthony Mascia
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio; Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Shelby McCauley
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Joseph Speth
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio; Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Stefanno Alarcon Nunez
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio; Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Gael Boivin
- Varian, a Siemens Healthineers Company, Palo Alto, California
| | - Marta Vilalta
- Varian, a Siemens Healthineers Company, Palo Alto, California
| | - Ricky A Sharma
- Varian, a Siemens Healthineers Company, Palo Alto, California
| | | | - Mathieu Sertorio
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio; Department of Radiation Oncology, University of Cincinnati Cancer Center, University of Cincinnati College of Medicine, Cincinnati, Ohio.
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Shukla S, Saha T, Rama N, Acharya A, Le T, Bian F, Donovan J, Tan LA, Vatner R, Kalinichenko V, Mascia A, Perentesis JP, Kalin TV. Ultra-high dose-rate proton FLASH improves tumor control. Radiother Oncol 2023; 186:109741. [PMID: 37315577 PMCID: PMC10527231 DOI: 10.1016/j.radonc.2023.109741] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 06/04/2023] [Accepted: 06/05/2023] [Indexed: 06/16/2023]
Abstract
BACKGROUND AND PURPOSE Proton radiotherapy (PRT) offers potential benefits over other radiation modalities, including photon and electron radiotherapy. Increasing the rate at which proton radiation is delivered may provide a therapeutic advantage. Here, we compared the efficacy of conventional proton therapy (CONVpr) to ultrahigh dose-rate proton therapy, FLASHpr, in a mouse model of non-small cell lung cancers (NSCLC). MATERIALS AND METHODS Mice bearing orthotopic lung tumors received thoracic radiation therapy using CONVpr (<0.05 Gy/s) and FLASHpr (>60 Gy/s) dose rates. RESULTS Compared to CONVpr, FLASHpr was more effective in reducing tumor burden and decreasing tumor cell proliferation. Furthermore, FLASHpr was more efficient in increasing the infiltration of cytotoxic CD8+ T-lymphocytes inside the tumor while simultaneously reducing the percentage of immunosuppressive regulatory T-cells (Tregs) among T-lymphocytes. Also, compared to CONVpr, FLASHpr was more effective in decreasing pro-tumorigenic M2-like macrophages in lung tumors, while increasing infiltration of anti-tumor M1-like macrophages. Finally, FLASHpr treatment reduced expression of checkpoint inhibitors in lung tumors, indicating reduced immune tolerance. CONCLUSIONS Our results suggest that FLASH dose-rate proton delivery modulates the immune system to improve tumor control and might thus be a promising new alternative to conventional dose rates for NSCLC treatment.
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Affiliation(s)
- Samriddhi Shukla
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States
| | - Taniya Saha
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States
| | - Nihar Rama
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States
| | - Anusha Acharya
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States
| | - Tien Le
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States
| | - Fenghua Bian
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States
| | - Johnny Donovan
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States
| | - Lin Abigail Tan
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States
| | - Ralph Vatner
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH, USA, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Vladimir Kalinichenko
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States; Neonatology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States; Center for Lung Regenerative Medicine, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States
| | - Anthony Mascia
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH, USA, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - John P Perentesis
- Cincinnati Children's Hospital Medical Center, Division of Oncology, Division of Experimental Hematology, Division of Biomedical Informatics, Cincinnati, OH 45229, USA
| | - Tanya V Kalin
- Division of Pulmonary Biology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States; Neonatology, the Perinatal Institute of Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, United States.
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Lourenço A, Lee N, Charlwood F, Lambert J, Vera-Sánchez JA, Hussein M, Shipley D, Romano F, Lowe M, Clarke M, Lorentini S, Mazal A, Pettingell J, Palmans H, Thomas R. A portable primary-standard level graphite calorimeter for absolute dosimetry in clinical pencil beam scanning proton beams. Phys Med Biol 2023; 68:175005. [PMID: 37414003 DOI: 10.1088/1361-6560/ace50f] [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: 12/06/2022] [Accepted: 07/06/2023] [Indexed: 07/08/2023]
Abstract
Objective. To report the use of a portable primary standard level graphite calorimeter for direct dose determination in clinical pencil beam scanning proton beams, which forms part of the recommendations of the proposed Institute of Physics and Engineering in Medicine (IPEM) Code of Practice (CoP) for proton therapy dosimetry.Approach. The primary standard proton calorimeter (PSPC) was developed at the National Physical Laboratory (NPL) and measurements were performed at four clinical proton therapy facilities that use pencil beam scanning for beam delivery. Correction factors for the presence of impurities and vacuum gaps were calculated and applied, as well as dose conversion factors to obtain dose to water. Measurements were performed in the middle of 10 × 10 × 10 cm3homogeneous dose volumes, centred at 10.0, 15.0 and 25.0 g·cm-2depth in water. The absorbed dose to water determined with the calorimeter was compared to the dose obtained using PTW Roos-type ionisation chambers calibrated in terms of absorbed dose to water in60Co applying the recommendations in the IAEA TRS-398 CoP.Main results.The relative dose difference between the two protocols varied between 0.4% and 2.1% depending on the facility. The reported overall uncertainty in the determination of absorbed dose to water using the calorimeter is 0.9% (k= 1), which corresponds to a significant reduction of uncertainty in comparison with the TRS-398 CoP (currently with an uncertainty equal or larger than 2.0% (k= 1) for proton beams).Significance. The establishment of a purpose-built primary standard and associated CoP will considerably reduce the uncertainty of the absorbed dose to water determination and ensure improved accuracy and consistency in the dose delivered to patients treated with proton therapy and bring proton reference dosimetry uncertainty in line with megavoltage photon radiotherapy.
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Affiliation(s)
- A Lourenço
- Medical Radiation Science Group, National Physical Laboratory, Teddington TW11 0LW, United Kingdom
- Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, United Kingdom
| | - N Lee
- Medical Radiation Science Group, National Physical Laboratory, Teddington TW11 0LW, United Kingdom
| | - F Charlwood
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester M20 4BX, United Kingdom
| | - J Lambert
- Rutherford Cancer Centre South Wales, Newport NP10 8FZ, United Kingdom
| | - J A Vera-Sánchez
- Centro de Protonterapia Quirónsalud, E-28223 Pozuelo de Alarcón, Madrid, Spain
| | - M Hussein
- Medical Radiation Science Group, National Physical Laboratory, Teddington TW11 0LW, United Kingdom
- Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, United Kingdom
| | - D Shipley
- Medical Radiation Science Group, National Physical Laboratory, Teddington TW11 0LW, United Kingdom
| | - F Romano
- Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Via S Sofia 64, I-95123, Catania, Italy
| | - M Lowe
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester M20 4BX, United Kingdom
| | - M Clarke
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester M20 4BX, United Kingdom
| | - S Lorentini
- Protontherapy Department, Azienda Provinciale per i Servizi Sanitari (APSS), Trento, Italy
| | - A Mazal
- Centro de Protonterapia Quirónsalud, E-28223 Pozuelo de Alarcón, Madrid, Spain
| | - J Pettingell
- Rutherford Cancer Centre North East, Bedlington NE22 7FD, United Kingdom
| | - H Palmans
- Medical Radiation Science Group, National Physical Laboratory, Teddington TW11 0LW, United Kingdom
- Medical Physics Group, MedAustron Ion Therapy Center, A-2700 Wiener Neustadt, Austria
| | - R Thomas
- Medical Radiation Science Group, National Physical Laboratory, Teddington TW11 0LW, United Kingdom
- University of Surrey, Faculty of Engineering and Physical Science, Guildford GU2 7XH, United Kingdom
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Motta S, Christensen JB, Togno M, Schäfer R, Safai S, Lomax AJ, Yukihara EG. Characterization of LiF:Mg,Ti thermoluminescence detectors in low-LET proton beams at ultra-high dose rates. Phys Med Biol 2023; 68. [PMID: 36696696 DOI: 10.1088/1361-6560/acb634] [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: 10/14/2022] [Accepted: 01/25/2023] [Indexed: 01/26/2023]
Abstract
Objective.This work aims at characterizing LiF:Mg,Ti thermoluminescence detectors (TLDs) for dosimetry of a 250 MeV proton beam delivered at ultra-high dose rates (UHDR). Possible dose rate effects in LiF:Mg,Ti, as well as its usability for dosimetry of narrow proton beams are investigated.Approach.LiF:Mg,Ti (TLD-100TMMicrocubes, 1 mm × 1 mm × 1 mm) was packaged in matrices of 5 × 5 detectors. The center of each matrix was irradiated with single-spot low-LET (energy >244 MeV) proton beam in the (1-4500) Gy s-1average dose rates range. A beam reconstruction procedure was applied to the detectors irradiated at the highest dose rate (Gaussian beam sigma <2 mm) to correct for volumetric averaging effects. Reference dosimetry was carried out with a diamond detector and radiochromic films. The delivered number of protons was measured by a Faraday cup, which was employed to normalize the detector responses.Main results.The lateral beam spread obtained from the beam reconstruction agreed with the one derived from the radiochromic film measurements. No dose rates effects were observed in LiF:Mg,Ti for the investigated dose rates within 3% (k= 1). On average, the dose response of the TLDs agreed with the reference detectors within their uncertainties. The largest deviation (-5%) was measured at 4500 Gy s-1.Significance.The dose rate independence of LiF:Mg,Ti TLDs makes them suitable for dosimetry of UHDR proton beams. Additionally, the combination of a matrix of TLDs and the beam reconstruction can be applied to determine the beam profile of narrow proton beams.
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Affiliation(s)
- S Motta
- Department of Radiation Safety and Security, Paul Scherrer Institute, Villigen PSI, Switzerland.,Department of Physics, ETH Zürich, Zürich, Switzerland
| | - J B Christensen
- Department of Radiation Safety and Security, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - M Togno
- Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - R Schäfer
- Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - S Safai
- Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - A J Lomax
- Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland.,Department of Physics, ETH Zürich, Zürich, Switzerland
| | - E G Yukihara
- Department of Radiation Safety and Security, Paul Scherrer Institute, Villigen PSI, Switzerland
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Bass GA, Shipley DR, Flynn SF, Thomas RAS. A prototype low-cost secondary standard calorimeter for reference dosimetry with ultra-high pulse dose rates. Br J Radiol 2023; 96:20220638. [PMID: 36259518 PMCID: PMC10997030 DOI: 10.1259/bjr.20220638] [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: 06/24/2022] [Revised: 09/05/2022] [Accepted: 09/25/2022] [Indexed: 11/29/2022] Open
Abstract
OBJECTIVES Ultra-high pulse dose rate modalities present significant dosimetry challenges for ionisation chambers due to significant ion recombination. Conversely, calorimeters are ideally suited to measure high dose, short duration dose deliveries and this work describes a simple calorimeter as an alternative dosemeter for use in the clinic. METHODS Calorimeters were constructed featuring a disc-shaped core and single sensing thermistor encased in a 3D-printed body shaped like a Roos ionisation chamber. The thermistor forms one arm of a DC Wheatstone bridge, connected to a standard DMM. The bridge-out-of-balance voltage was calibrated in terms of temperature. A graphite-core calorimeter was calibrated in terms of absorbed dose to water (J/kg) in Co-60 and conventional 6, 10 and 15 MV X-rays. Similarly, an aluminium-core calorimeter was calibrated in a conventional 20 MeV electron beam and tested in a research high dose per pulse 6 MeV electron beam. RESULTS Calorimeters were successfully calibrated in terms of absorbed dose to water in conventional radiotherapy beams at approximately 5 Gy/min with an estimated uncertainty of ±2-2.5% (k = 2), and performed similarly in a 6 MeV electron beam delivering approximately 180 Gy/s. CONCLUSIONS A simple, low-cost calorimeter traceably calibrated to existing primary standards of absorbed dose could be used as a secondary standard for dosimetry for ultra-high pulse dose rates in the clinic. ADVANCES IN KNOWLEDGE Secondary standard calorimeters for routine measurements are not available commercially; this work presents the basis of a simple, low-cost solution for reference dosimetry for ultra-high pulse dose rate beams.
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Affiliation(s)
- Graham A Bass
- Medical Radiation Physics, National Physical Laboratory,
Hampton Road, Teddington, Middlesex, United Kingdom
| | - David R Shipley
- Medical Radiation Physics, National Physical Laboratory,
Hampton Road, Teddington, Middlesex, United Kingdom
| | - Samuel F Flynn
- Medical Radiation Physics, National Physical Laboratory,
Hampton Road, Teddington, Middlesex, United Kingdom
| | - Russell A S Thomas
- Medical Radiation Physics, National Physical Laboratory,
Hampton Road, Teddington, Middlesex, United Kingdom
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