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Vidal M, Gérard A, Floquet V, Forthomme J, Christensen JB, Almhagen E, Grusell E, Heymans V, Rossomme S, Dumas S, Trimaud R, Hérault J. Beam monitor chamber calibration of a synchro-cyclotron high dose rate per pulse pulsed scanned proton beam. Phys Med Biol 2024; 69:085016. [PMID: 38252970 DOI: 10.1088/1361-6560/ad2123] [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: 06/15/2022] [Accepted: 01/22/2024] [Indexed: 01/24/2024]
Abstract
Objective. Ionization chambers, mostly used for beam calibration and for reference dosimetry, can show high recombination effects in pulsed high dose rate proton beams. The aims of this paper are: first, to characterize the linearity response of newly designed asymmetrical beam monitor chambers (ABMC) in a 100-226 MeV pulsed high dose rate per pulse scanned proton beam; and secondly, to calibrate the ABMC with a PPC05 (IBA Dosimetry) plane parallel ionization chamber and compare to calibration with a home-made Faraday cup (FC).Approach. The ABMC response linearity was evaluated with both the FC and a PTW 60019 microDiamond detector. Regarding ionometry-based ABMC calibration, recombination factors were evaluated theoretically, then numerically, and finally experimentally measured in water for a plane parallel ionization chamber PPC05 (IBA Dosimetry) throughkssaturation curves. Finally, ABMC calibration was also achieved with FC and compared to the ionometry method for 7 energies.Main results. Linearity measurements showed that recombination losses in the new ABMC design were well taken into account for the whole range of the machine dose rates. The two-voltage-method was not suitable for recombination correction, but Jaffé's plots analysis was needed, emphasizing the current IAEA TRS-398 reference protocol limitations. Concerning ABMC calibration, FC based absorbed dose estimation and PPC05-based absorbed dose estimation differ by less than 6.3% for the investigated energies.Significance.So far, no update on reference dosimetry protocols is available to estimate the absorbed dose in ionization chambers for clinical high dose rate per pulse pulsed scanned proton beams. This work proposes a validation of the new ABMC design, a method to take into account the recombination effect for ionometry-based ABMC calibration and a comparison with FC dose estimation in this type of proton beams.
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Affiliation(s)
- Marie Vidal
- Institut Méditerranéen de Protonthérapie-Centre Antoine Lacassagne, Fédération Claude Lalanne, Nice, France
| | - Anaïs Gérard
- Institut Méditerranéen de Protonthérapie-Centre Antoine Lacassagne, Fédération Claude Lalanne, Nice, France
| | - Vincent Floquet
- Institut Méditerranéen de Protonthérapie-Centre Antoine Lacassagne, Fédération Claude Lalanne, Nice, France
| | | | - Jeppe Brage Christensen
- DTU Health Tech, Technical University of Denmark, Roskilde, Denmark
- Department of Radiation Safety and Security, Paul Scherrer Institute, PSI Villigen, Switzerland
| | - Erik Almhagen
- Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science-Skandion Clinics Uppsala, Sweden
| | - Erik Grusell
- Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science-Skandion Clinics Uppsala, Sweden
| | | | | | - Serge Dumas
- Institut Méditerranéen de Protonthérapie-Centre Antoine Lacassagne, Fédération Claude Lalanne, Nice, France
| | - Richard Trimaud
- Institut Méditerranéen de Protonthérapie-Centre Antoine Lacassagne, Fédération Claude Lalanne, Nice, France
| | - Joël Hérault
- Institut Méditerranéen de Protonthérapie-Centre Antoine Lacassagne, Fédération Claude Lalanne, Nice, France
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Jeon C, Ahn S, Amano D, Kamiguchi N, Cho S, Sheen H, Park HC, Han Y. FLASH dose rate calculation based on log files in proton pencil beam scanning therapy. Med Phys 2023; 50:7154-7166. [PMID: 37431587 DOI: 10.1002/mp.16575] [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: 11/30/2022] [Revised: 06/05/2023] [Accepted: 06/06/2023] [Indexed: 07/12/2023] Open
Abstract
BACKGROUND In radiation therapy, irradiating healthy normal tissues in the beam trajectories is inevitable. This unnecessary dose means that patients undergoing treatment risk developing side effects. Recently, FLASH radiotherapy delivering ultra-high-dose-rate beams has been re-examined because of its normal-tissue-sparing effect. To confirm the mean and instantaneous dose rates of the FLASH beam, stable and accurate dosimetry is required. PURPOSE Detailed verification of the FLASH effect requires dosimeters and a method to measure the average and instantaneous dose rate stably for 2- or 3-dimensional dose distributions. To verify the delivered FLASH beam, we utilized machine log files from the built-in monitor chamber to develop a dosimetry method to calculate the dose and average/instantaneous dose rate distributions in two or three dimensions in a phantom. METHODS To create a spread-out Bragg peak (SOBP) and deliver a uniform dose in a target, a mini-ridge filter was created with a 3D printer. Proton pencil beam line scanning plans of 2 × 2 cm2 , 3 × 3 cm2 , 4 × 4 cm2 , and round shapes with 2.3 cm diameter patterns delivering 230 MeV energy protons were created. The absorbed dose in the solid water phantom of each plan was measured using a PPC05 ionization chamber (IBA Dosimetry, Virginia, USA) in the SOBP region, and the log files for each plan were exported from the treatment control system console. Using these log files, the delivered dose and average dose rate were calculated using two methods: a direct method and a Monte Carlo (MC) simulation method that uses log file information. The computed and average dose rates were compared with the ionization chamber measurements. Additionally, instantaneous dose rates in user-defined volumes were calculated using the MC simulation method with a temporal resolution of 5 ms. RESULTS Compared to ionization chamber dosimetry, 10 of 12 cases using the direct calculation method and 9 of 11 cases using the MC method had a dose difference below ±3%. Nine of 12 cases using the direct calculation method and 8 of 11 cases using the MC method had dose rate differences below ±3%. The average and maximum dose differences for the direct calculation and MC method were-0.17, +0.72%, and -3.15, +3.32%, respectively. For the dose rate difference, the average and maximum for the direct calculation and MC method were +1.26, +1.12%, and +3.75, +3.15%, respectively. In the instantaneous dose rate calculation with the MC simulation, a large fluctuation with a maximum of 163 Gy/s and a minimum of 4.29 Gy/s instantaneous dose rate was observed in a specific position, whereas the mean dose rate was 62 Gy/s. CONCLUSIONS We successfully developed methods in which machine log files are used to calculate the dose and the average and instantaneous dose rates for FLASH radiotherapy and demonstrated the feasibility of verifying the delivered FLASH beams.
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Affiliation(s)
- Chanil Jeon
- Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul, Republic of Korea
| | - Sunghwan Ahn
- Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Daizo Amano
- Sumitomo Heavy Industries, Ltd, Tokyo, Japan
| | | | - Sungkoo Cho
- Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Heesoon Sheen
- Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Hee Chul Park
- Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Youngyih Han
- Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul, Republic of Korea
- Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
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Ehwald J, Togno M, Lomax AJ, Weber DC, Safai S, Winterhalter C. Detailed Monte-Carlo characterization of a Faraday cup for proton therapy. Med Phys 2023; 50:5828-5841. [PMID: 37227735 DOI: 10.1002/mp.16464] [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: 06/07/2022] [Revised: 04/03/2023] [Accepted: 04/09/2023] [Indexed: 05/26/2023] Open
Abstract
BACKGROUND Experiments with ultra-high dose rates in proton therapy are of increasing interest for potential treatment benefits. The Faraday Cup (FC) is an important detector for the dosimetry of such ultra-high dose rate beams. So far, there is no consensus on the optimal design of a FC, or on the influence of beam properties and magnetic fields on shielding of the FC from secondary charged particles. PURPOSE To perform detailed Monte Carlo simulations of a Faraday cup to identify and quantify all the charge contributions from primary protons and secondary particles that modify the efficiency of the FC response as a function of a magnetic field employed to improve the detector's reading. METHODS In this paper, a Monte Carlo (MC) approach was used to investigate the Paul Scherrer Institute (PSI) FC and quantify contributions of charged particles to its signal for beam energies of 70, 150, and 228 MeV and magnetic fields between 0 and 25 mT. Finally, we compared our MC simulations to measurements of the response of the PSI FC. RESULTS For maximum magnetic fields, the efficiency (signal of the FC normalized to charged delivered by protons) of the PSI FC varied between 99.97% and 100.22% for the lowest and highest beam energy. We have shown that this beam energy-dependence is mainly caused by contributions of secondary charged particles, which cannot be fully suppressed by the magnetic field. Additionally, it has been demonstrated that these contributions persist, making the FC efficiency beam energy dependent for fields up to 250 mT, posing inevitable limits on the accuracy of FC measurements if not corrected. In particular, we have identified a so far unreported loss of electrons via the outer surfaces of the absorber block and show the energy distributions of secondary electrons ejected from the vacuum window (VW) (up to several hundred keV), together with electrons ejected from the absorber block (up to several MeV). Even though, in general, simulations and measurements were well in agreement, the limitation of the current MC calculations to produce secondary electrons below 990 eV posed a limit in the efficiency simulations in the absence of a magnetic field as compared to the experimental data. CONCLUSION TOPAS-based MC simulations allowed to identify various and previously unreported contributions to the FC signal, which are likely to be present in other FC designs. Estimating the beam energy dependence of the PSI FC for additional beam energies could allow for the implementation of an energy-dependent correction factor to the signal. Dose estimates, based on accurate measurements of the number of delivered protons, provided a valid instrument to challenge the dose determined by reference ionization chambers, not only at ultra-high dose rates but also at conventional dose rates.
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Affiliation(s)
- Julian Ehwald
- Centre for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
- Department of Physics, ETH Zurich, Zurich, Switzerland
| | - Michele Togno
- Centre for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Antony John Lomax
- Centre for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
- Department of Physics, ETH Zurich, Zurich, Switzerland
| | - Damien Charles Weber
- Centre for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
- Radiation Oncology Department of University Hospital of Bern, Bern, Switzerland
- Radiation Oncology Department of University Hospital of Zurich, Zurich, Switzerland
| | - Sairos Safai
- Centre for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Carla Winterhalter
- Centre for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
- Department of Physics, ETH Zurich, Zurich, Switzerland
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Yap J, De Franco A, Sheehy S. Future Developments in Charged Particle Therapy: Improving Beam Delivery for Efficiency and Efficacy. Front Oncol 2021; 11:780025. [PMID: 34956897 PMCID: PMC8697351 DOI: 10.3389/fonc.2021.780025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/16/2021] [Indexed: 01/09/2023] Open
Abstract
The physical and clinical benefits of charged particle therapy (CPT) are well recognized. However, the availability of CPT and complete exploitation of dosimetric advantages are still limited by high facility costs and technological challenges. There are extensive ongoing efforts to improve upon these, which will lead to greater accessibility, superior delivery, and therefore better treatment outcomes. Yet, the issue of cost remains a primary hurdle as utility of CPT is largely driven by the affordability, complexity and performance of current technology. Modern delivery techniques are necessary but limited by extended treatment times. Several of these aspects can be addressed by developments in the beam delivery system (BDS) which determines the overall shaping and timing capabilities enabling high quality treatments. The energy layer switching time (ELST) is a limiting constraint of the BDS and a determinant of the beam delivery time (BDT), along with the accelerator and other factors. This review evaluates the delivery process in detail, presenting the limitations and developments for the BDS and related accelerator technology, toward decreasing the BDT. As extended BDT impacts motion and has dosimetric implications for treatment, we discuss avenues to minimize the ELST and overview the clinical benefits and feasibility of a large energy acceptance BDS. These developments support the possibility of advanced modalities and faster delivery for a greater range of treatment indications which could also further reduce costs. Further work to realize methodologies such as volumetric rescanning, FLASH, arc, multi-ion and online image guided therapies are discussed. In this review we examine how increased treatment efficiency and efficacy could be achieved with improvements in beam delivery and how this could lead to faster and higher quality treatments for the future of CPT.
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Affiliation(s)
- Jacinta Yap
- School of Physics, University of Melbourne, Melbourne, VIC, Australia
| | - Andrea De Franco
- IFMIF Accelerator Development Group, Rokkasho Fusion Institute, National Institutes for Quantum Science and Technology, Aomori, Japan
| | - Suzie Sheehy
- School of Physics, University of Melbourne, Melbourne, VIC, Australia
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Maradia V, Meer D, Weber DC, Lomax AJ, Schippers JM, Psoroulas S. A new emittance selection system to maximize beam transmission for low-energy beams in cyclotron-based proton therapy facilities with gantry. Med Phys 2021; 48:7613-7622. [PMID: 34655083 PMCID: PMC9298197 DOI: 10.1002/mp.15278] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 08/24/2021] [Accepted: 10/03/2021] [Indexed: 02/06/2023] Open
Abstract
Purpose In proton therapy, the potential of using high‐dose rates in the cancer treatment is being explored. High‐dose rates could improve efficiency and throughput in standard clinical practice, allow efficient utilization of motion mitigation techniques for moving targets, and potentially enhance normal tissue sparing due to the so‐called FLASH effect. However, high‐dose rates are difficult to reach when lower energy beams are applied in cyclotron‐based proton therapy facilities, because they result in large beam sizes and divergences downstream of the degrader, incurring large losses from the cyclotron to the patient position (isocenter). In current facilities, the emittance after the degrader is reduced using circular collimators; however, this does not provide an optimal matching to the acceptance of the following beamline, causing a low transmission for these energies. We, therefore, propose to use a collimation system, asymmetric in both beam size and divergence, resulting in symmetric emittance in both beam transverse planes as required for a gantry system. This new emittance selection, together with a new optics design for the following beamline and gantry, allows a better matching to the beamline acceptance and an improvement of the transmission. Methods We implemented a custom method to design the collimator sizes and shape required to select high emittance, to be transported by the following beamline using new beam optics (designed with TRANSPORT) to maximize acceptance matching. For predicting the transmission in the new configuration (new collimators + optics), we used Monte Carlo simulations implemented in BDSIM, implementing a model of PSI Gantry 2 which we benchmarked against measurements taken in the current clinical scenario (circular collimators + clinical optics). Results From the BDSIM simulations, we found that the new collimator system and matching beam optics results in an overall transmission from the cyclotron to the isocenter for a 70 MeV beam of 0.72%. This is an improvement of almost a factor of 6 over the current clinical performance (0.13% transmission). The new optics satisfies clinical beam requirements at the isocenter. Conclusions We developed a new emittance collimation system for PSI's PROSCAN beamline which, by carefully selecting beam size and divergence asymmetrically, increases the beam transmission for low‐energy beams in current state‐of‐the‐art cyclotron‐based proton therapy gantries. With these improvements, we could predict almost 1% transmission for low‐energy beams at PSI's Gantry 2. Such a system could easily be implemented in facilities interested in increasing dose rates for efficient motion mitigation and FLASH experiments alike.
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Affiliation(s)
- Vivek Maradia
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.,Department of Physics, ETH Zurich, Zurich, Switzerland
| | - David Meer
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland
| | - Damien Charles Weber
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.,Department of Radiation Oncology, University Hospital Zurich, Zurich, Switzerland.,Department of Radiation Oncology, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Antony John Lomax
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.,Department of Physics, ETH Zurich, Zurich, Switzerland
| | | | - Serena Psoroulas
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland
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Diffenderfer ES, Sørensen BS, Mazal A, Carlson DJ. The current status of preclinical proton FLASH radiation and future directions. Med Phys 2021; 49:2039-2054. [PMID: 34644403 DOI: 10.1002/mp.15276] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 09/12/2021] [Accepted: 09/17/2021] [Indexed: 11/05/2022] Open
Abstract
We review the current status of proton FLASH experimental systems, including preclinical physical and biological results. Technological limitations on preclinical investigation of FLASH biological mechanisms and determination of clinically relevant parameters are discussed. A review of the biological data reveals no reproduced proton FLASH effect in vitro and a significant in vivo FLASH sparing effect of normal tissue toxicity observed with multiple proton FLASH irradiation systems. Importantly, multiple studies suggest little or no difference in tumor growth delay for proton FLASH when compared to conventional dose rate proton radiation. A discussion follows on future areas of development with a focus on the determination of the optimal parameters for maximizing the therapeutic ratio between tumor and normal tissue response and ultimately clinical translation of proton FLASH radiation.
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Affiliation(s)
- Eric S Diffenderfer
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Brita S Sørensen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Alejandro Mazal
- Department of Medical Physics, Centro de Protonterapia Quironsalud, Madrid, Spain
| | - David J Carlson
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Chua KLM, Chu PL, Tng DJH, Soo KC, Chua MLK. Repurposing Proton Beam Therapy through Novel Insights into Tumour Radioresistance. Clin Oncol (R Coll Radiol) 2021; 33:e469-e481. [PMID: 34509347 DOI: 10.1016/j.clon.2021.08.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 08/02/2021] [Accepted: 08/25/2021] [Indexed: 12/11/2022]
Abstract
Despite improvements in radiotherapy, radioresistance remains an important clinical challenge. Radioresistance can be mediated through enhanced DNA damage response mechanisms within the tumour or through selective pressures exerted by the tumour microenvironment (TME). The effects of the TME have in recent times gained increased attention, in part due to the success of immune modulating strategies, but also through improved understanding of the downstream effects of hypoxia and dysregulated wound healing processes on mediating radioresistance. Although we have a better appreciation of these molecular mechanisms, efforts to address them through novel combination approaches have been scarce, owing to limitations of photon therapy and concerns over toxicity. At the same time, proton beam therapy (PBT) represents an advancement in radiotherapy technologies. However, early clinical results have been mixed and the clinical strategies around optimal use and patient selection for PBT remain unclear. Here we highlight the role that PBT can play in addressing radioresistance, through better patient selection, and by providing an improved toxicity profile for integration with novel agents. We will also describe the developments around FLASH PBT. Through close examination of its normal tissue-sparing effects, we will highlight how FLASH PBT can facilitate combination strategies to tackle radioresistance by further improving toxicity profiles and by directly mediating the mechanisms of radioresistance.
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Affiliation(s)
- K L M Chua
- Oncology Academic Clinical Programme, Duke-NUS Medical School, Singapore; Division of Radiation Oncology, National Cancer Centre Singapore, Singapore
| | - P L Chu
- Oncology Academic Clinical Programme, Duke-NUS Medical School, Singapore
| | - D J H Tng
- Division of Radiation Oncology, National Cancer Centre Singapore, Singapore
| | - K C Soo
- Division of Medical Sciences, National Cancer Centre Singapore, Singapore; Division of Surgical Oncology, National Cancer Centre Singapore, Singapore
| | - M L K Chua
- Oncology Academic Clinical Programme, Duke-NUS Medical School, Singapore; Division of Radiation Oncology, National Cancer Centre Singapore, Singapore; Division of Medical Sciences, National Cancer Centre Singapore, Singapore.
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