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Bobić M, Christensen JB, Lee H, Choulilitsa E, Czerska K, Togno M, Safai S, Yukihara EG, Winey BA, Lomax AJ, Paganetti H, Albertini F, Nesteruk KP. Optically stimulated luminescence dosimeters for simultaneous measurement of point dose and dose-weighted LET in an adaptive proton therapy workflow. Front Oncol 2024; 13:1333039. [PMID: 38510267 PMCID: PMC10951997 DOI: 10.3389/fonc.2023.1333039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Accepted: 12/18/2023] [Indexed: 03/22/2024] Open
Abstract
Purpose To demonstrate the suitability of optically stimulated luminescence detectors (OSLDs) for accurate simultaneous measurement of the absolute point dose and dose-weighted linear energy transfer (LETD) in an anthropomorphic phantom for experimental validation of daily adaptive proton therapy. Methods A clinically realistic intensity-modulated proton therapy (IMPT) treatment plan was created based on a CT of an anthropomorphic head-and-neck phantom made of tissue-equivalent material. The IMPT plan was optimized with three fields to deliver a uniform dose to the target volume covering the OSLDs. Different scenarios representing inter-fractional anatomical changes were created by modifying the phantom. An online adaptive proton therapy workflow was used to recover the daily dose distribution and account for the applied geometry changes. To validate the adaptive workflow, measurements were performed by irradiating Al2O3:C OSLDs inside the phantom. In addition to the measurements, retrospective Monte Carlo simulations were performed to compare the absolute dose and dose-averaged LET (LETD) delivered to the OSLDs. Results The online adaptive proton therapy workflow was shown to recover significant degradation in dose conformity resulting from large anatomical and positioning deviations from the reference plan. The Monte Carlo simulations were in close agreement with the OSLD measurements, with an average relative error of 1.4% for doses and 3.2% for LETD. The use of OSLDs for LET determination allowed for a correction for the ionization quenched response. Conclusion The OSLDs appear to be an excellent detector for simultaneously assessing dose and LET distributions in proton irradiation of an anthropomorphic phantom. The OSLDs can be cut to almost any size and shape, making them ideal for in-phantom measurements to probe the radiation quality and dose in a predefined region of interest. Although we have presented the results obtained in the experimental validation of an adaptive proton therapy workflow, the same approach can be generalized and used for a variety of clinical innovations and workflow developments that require accurate assessment of point dose and/or average LET.
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Affiliation(s)
- Mislav Bobić
- Department of Physics, ETH Zurich, Zurich, Switzerland
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
| | | | - Hoyeon Lee
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
| | - Evangelia Choulilitsa
- Department of Physics, ETH Zurich, Zurich, Switzerland
- Paul Scherrer Institute, Villigen, Switzerland
| | | | | | | | | | - Brian A. Winey
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
| | - Antony J. Lomax
- Department of Physics, ETH Zurich, Zurich, Switzerland
- Paul Scherrer Institute, Villigen, Switzerland
| | - Harald Paganetti
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
| | | | - Konrad P. Nesteruk
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
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Almeida A, Togno M, Ballesteros-Zebadua P, Franco-Perez J, Geyer R, Schaefer R, Petit B, Grilj V, Meer D, Safai S, Lomax T, Weber DC, Bailat C, Psoroulas S, Vozenin MC. Dosimetric and biologic intercomparison between electron and proton FLASH beams. Radiother Oncol 2024; 190:109953. [PMID: 37839557 DOI: 10.1016/j.radonc.2023.109953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 10/07/2023] [Accepted: 10/11/2023] [Indexed: 10/17/2023]
Abstract
BACKGROUND AND PURPOSE The FLASH effect has been validated in different preclinical experiments with electrons (eFLASH) and protons (pFLASH) operating at an average dose rate above 40 Gy/s. However, no systematic intercomparison of the FLASH effect produced by eFLASHvs. pFLASH has yet been performed and constitutes the aim of the present study. MATERIALS AND METHODS The electron eRT6/Oriatron/CHUV/5.5 MeV and proton Gantry1/PSI/170 MeV were used to deliver conventional (0.1 Gy/s eCONV and pCONV) and FLASH (≥110 Gy/s eFLASH and pFLASH) dose rates. Protons were delivered in transmission. Dosimetric and biologic intercomparisons were performed using previously validated dosimetric approaches and experimental murine models. RESULTS The difference between the average absorbed dose measured at Gantry 1 with PSI reference dosimeters and with CHUV/IRA dosimeters was -1.9 % (0.1 Gy/s) and + 2.5 % (110 Gy/s). The neurocognitive capacity of eFLASH and pFLASH irradiated mice was indistinguishable from the control, while both eCONV and pCONV irradiated cohorts showed cognitive decrements. Complete tumor response was obtained after an ablative dose of 20 Gy delivered with the two beams at CONV and FLASH dose rates. Tumor rejection upon rechallenge indicates that anti-tumor immunity was activated independently of the beam-type and the dose-rate. CONCLUSION Despite major differences in the temporal microstructure of proton and electron beams, this study shows that dosimetric standards can be established. Normal brain protection and tumor control were produced by the two beams. More specifically, normal brain protection was achieved when a single dose of 10 Gy was delivered in 90 ms or less, suggesting that the most important physical parameter driving the FLASH sparing effect might be the mean dose rate. In addition, a systemic anti-tumor immunological memory response was observed in mice exposed to high ablative dose of electron and proton delivered at CONV and FLASH dose rate.
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Affiliation(s)
- A Almeida
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - M Togno
- Center for Proton Therapy, Paul Scherrer Institute, 5323, Villigen, Switzerland
| | - P Ballesteros-Zebadua
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland; Instituto Nacional de Neurología y Neurocirugía MVS, Mexico City, Mexico
| | - J Franco-Perez
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland; Instituto Nacional de Neurología y Neurocirugía MVS, Mexico City, Mexico
| | - R Geyer
- Department of Radiation Oncology, lnselspital, Bern University Hospital, University of Bern, Switzerland
| | - R Schaefer
- Center for Proton Therapy, Paul Scherrer Institute, 5323, Villigen, Switzerland
| | - B Petit
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - V Grilj
- Institute of Radiation Physics (IRA)/CHUV, Lausanne University Hospital, Lausanne, Switzerland
| | - D Meer
- Center for Proton Therapy, Paul Scherrer Institute, 5323, Villigen, Switzerland
| | - S Safai
- Center for Proton Therapy, Paul Scherrer Institute, 5323, Villigen, Switzerland
| | - T Lomax
- Center for Proton Therapy, Paul Scherrer Institute, 5323, Villigen, Switzerland
| | - D C Weber
- Center for Proton Therapy, Paul Scherrer Institute, 5323, Villigen, Switzerland; Department of Radiation Oncology, lnselspital, Bern University Hospital, University of Bern, Switzerland; Department of Radiation Oncology, University Hospital of Zurich, Switzerland
| | - C Bailat
- Institute of Radiation Physics (IRA)/CHUV, Lausanne University Hospital, Lausanne, Switzerland
| | - S Psoroulas
- Center for Proton Therapy, Paul Scherrer Institute, 5323, Villigen, Switzerland
| | - Marie-Catherine Vozenin
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland; Radiotherapy and Radiobiology sector, Radiation Therapy service, University hospital of Geneva, Geneva, Switzerland.
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Christensen JB, Muñoz ID, Bassler N, Stengl C, Bossin L, Togno M, Safai S, Jaekel O, Yukihara EG. Optically stimulated luminescence detectors for dosimetry and LET measurements in light ion beams. Phys Med Biol 2023. [PMID: 37336242 DOI: 10.1088/1361-6560/acdfb0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
Objective: This work investigates the use of Al2O3:C and Al2O3:C,Mg optically stimulated luminescence (OSL) detectors to determine both the dose and the radiation quality in light ion beams. The radiation quality is here expressed through either the linear energy transfer (LET) or the closely related metric Qeff, which depends on the particle's speed and effective charge. The derived LET and Qeffvalues are applied to improve the dosimetry in light ion beams.

Approach: OSL detectors were irradiated in mono-energetic1H-,4He-,12C-, and16O-ion beams. The OSL signal is associated with two emission bands that were separated using a pulsed stimulation technique and subjected to automatic corrections based on reference irradiations. Each emission band was investigated independently for dosimetry, and the ratio of the two emission intensities was parameterized as a function of fluence- and dose-averaged LET, as well as Qeff. The determined radiation quality was subsequently applied to correct the dose for ionization quenching.

Main results: For both materials, the Qeffdeterminations in1H- and4He-ion beams are within 5 % of the Monte Carlo simulated values. Using the determined radiation quality metrics to correct the non-linear (ionization quenched) detector response leads to doses within 2 % of the reference doses. 

Significance: Al2O3:C and Al2O3:C,Mg OSL detectors are applicable for dosimetry and radiation quality estimations in1H- and4He-ions. Only Al2O3:C,Mg shows promising results for dosimetry in12C-ions. Across both materials and the investigated ions, the estimated Qeffvalues were less sensitive to the ion type than the estimated LET values. The reduced uncertainties suggest new possibilities for simultaneously estimating the physical and biological dose in particle therapy with OSL detectors.
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Affiliation(s)
- Jeppe Brage Christensen
- Department of Radiation Safety and Security, Paul Scherrer Institut PSI, Forschungsstrasse 111, Villigen, Aargau, 5232, SWITZERLAND
| | - Iván Domingo Muñoz
- Department of Physics and Astronomy, Heidelberg University Department of Physics and Astronomy, Im Neuenheimer Feld 226, Heidelberg, Baden-Württemberg, 69120, GERMANY
| | - Niels Bassler
- Department of Clinical Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, Aarhus, Midtjylland, 8000, DENMARK
| | - Christina Stengl
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Heidelberg, 69120, GERMANY
| | - Lily Bossin
- Department of Radiation Safety and Security, Paul Scherrer Institut PSI, Forschungsstrasse 111, Villigen, Aargau, 5232, SWITZERLAND
| | - Michele Togno
- Center for Proton Therapy, Paul Scherrer Institut, Forschungsstrasse 111, Villigen PSI, 5232, SWITZERLAND
| | - Sairos Safai
- Center for Proton Therapy, Paul Scherrer Institute, WMSA/C12, Villigen - PSI, 5232, SWITZERLAND
| | - Oliver Jaekel
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Heidelberg, 69120, GERMANY
| | - Eduardo G Yukihara
- Department of Radiation Safety and Security, Paul Scherrer Institut PSI, Forschungsstrasse 111, Villigen, Aargau, 5232, SWITZERLAND
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Almeida A, Togno M, Ballesteros-Zebadua P, Franco-Perez J, Geyer R, Schaefer R, Petit B, Grilj V, Meer D, Safai S, Lomax T, Weber DC, Bailat C, Psoroulas S, Vozenin MC. Dosimetric and biologic intercomparison between electron and proton FLASH beams. bioRxiv 2023:2023.04.20.537497. [PMID: 37131769 PMCID: PMC10153243 DOI: 10.1101/2023.04.20.537497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Background and purpose The FLASH effect has been validated in different preclinical experiments with electrons (eFLASH) and protons (pFLASH) operating at a mean dose rate above 40 Gy/s. However, no systematic intercomparison of the FLASH effect produced by e vs. pFLASH has yet been performed and constitutes the aim of the present study. Materials and methods The electron eRT6/Oriatron/CHUV/5.5 MeV and proton Gantry1/PSI/170 MeV were used to deliver conventional (0.1 Gy/s eCONV and pCONV) and FLASH (≥100 Gy/s eFLASH and pFLASH) irradiation. Protons were delivered in transmission. Dosimetric and biologic intercomparisons were performed with previously validated models. Results Doses measured at Gantry1 were in agreement (± 2.5%) with reference dosimeters calibrated at CHUV/IRA. The neurocognitive capacity of e and pFLASH irradiated mice was indistinguishable from the control while both e and pCONV irradiated cohorts showed cognitive decrements. Complete tumor response was obtained with the two beams and was similar between e and pFLASH vs. e and pCONV. Tumor rejection was similar indicating that T-cell memory response is beam-type and dose-rate independent. Conclusion Despite major differences in the temporal microstructure, this study shows that dosimetric standards can be established. The sparing of brain function and tumor control produced by the two beams were similar, suggesting that the most important physical parameter driving the FLASH effect is the overall time of exposure which should be in the range of hundreds of milliseconds for WBI in mice. In addition, we observed that immunological memory response is similar between electron and proton beams and is independent off the dose rate.
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Affiliation(s)
- A Almeida
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - M Togno
- Center for Proton Therapy, Paul Scherrer Institute, 5323 Villigen PSI, Switzerland
| | - P Ballesteros-Zebadua
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
- Instituto Nacional de Neurología y Neurocirugía MVS, Mexico City, Mexico
| | - J Franco-Perez
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
- Instituto Nacional de Neurología y Neurocirugía MVS, Mexico City, Mexico
| | - R Geyer
- Department of Radiation Oncology, lnselspital, Bern University Hospital, University of Bern, Switzerland
| | - R Schaefer
- Center for Proton Therapy, Paul Scherrer Institute, 5323 Villigen PSI, Switzerland
| | - B Petit
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - V Grilj
- Institute of Radiation Physics (IRA)/CHUV, Lausanne University Hospital, Lausanne, Switzerland
| | - D Meer
- Center for Proton Therapy, Paul Scherrer Institute, 5323 Villigen PSI, Switzerland
| | - S Safai
- Center for Proton Therapy, Paul Scherrer Institute, 5323 Villigen PSI, Switzerland
| | - T Lomax
- Center for Proton Therapy, Paul Scherrer Institute, 5323 Villigen PSI, Switzerland
| | - D C Weber
- Center for Proton Therapy, Paul Scherrer Institute, 5323 Villigen PSI, Switzerland
- Department of Radiation Oncology, lnselspital, Bern University Hospital, University of Bern, Switzerland
- Department of Radiation Oncology, University Hospital of Zurich, Switzerland
| | - C Bailat
- Institute of Radiation Physics (IRA)/CHUV, Lausanne University Hospital, Lausanne, Switzerland
| | - S Psoroulas
- Center for Proton Therapy, Paul Scherrer Institute, 5323 Villigen PSI, Switzerland
| | - M C Vozenin
- Laboratory of Radiation Oncology/Radiation Oncology Service/Department of Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Togno M, Nesteruk KP, Schäfer R, Psoroulas S, Meer D, Grossmann M, Christensen JB, Yukihara EG, Lomax AJ, Weber DC, Safai S. Ultra-high dose rate dosimetry for pre-clinical experiments with mm-small proton fields. Phys Med 2022; 104:101-111. [PMID: 36395638 DOI: 10.1016/j.ejmp.2022.10.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 10/10/2022] [Accepted: 10/23/2022] [Indexed: 11/15/2022] Open
Abstract
PURPOSE To characterize an experimental setup for ultra-high dose rate (UHDR) proton irradiations, and to address the challenges of dosimetry in millimetre-small pencil proton beams. METHODS At the PSI Gantry 1, high-energy transmission pencil beams can be delivered to biological samples and detectors up to a maximum local dose rate of ∼9000 Gy/s. In the presented setup, a Faraday cup is used to measure the delivered number of protons up to ultra-high dose rates. The response of transmission ion-chambers, as well as of different field detectors, was characterized over a wide range of dose rates using the Faraday cup as reference. RESULTS The reproducibility of the delivered proton charge was better than 1 % in the proposed experimental setup. EBT3 films, Al2O3:C optically stimulated luminescence detectors and a PTW microDiamond were used to validate the predicted dose. Transmission ionization chambers showed significant volume ion-recombination (>30 % in the tested conditions) which can be parametrized as a function of the maximum proton current density. Over the considered range, EBT3 films, inorganic scintillator-based screens and the PTW microDiamond were demonstrated to be dose rate independent within ±3 %, ±1.8 % and ±1 %, respectively. CONCLUSIONS Faraday cups are versatile dosimetry instruments that can be used for dose estimation, field detector characterization and on-line dose verification for pre-clinical experiments in UHDR proton pencil beams. Among the tested detectors, the commercial PTW microDiamond was found to be a suitable option to measure real time the dosimetric properties of narrow pencil proton beams for dose rates up to 2.2 kGy/s.
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Affiliation(s)
- M Togno
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland.
| | - K P Nesteruk
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, USA
| | - R Schäfer
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland
| | - S Psoroulas
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland
| | - D Meer
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland
| | - M Grossmann
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland
| | - J B Christensen
- Department of Radiation Safety and Security, Paul Scherrer Institut, Villigen, Switzerland
| | - E G Yukihara
- Department of Radiation Safety and Security, Paul Scherrer Institut, Villigen, Switzerland
| | - A J Lomax
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland; Department of Physics, ETH Zurich, Zurich, Switzerland
| | - D C Weber
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland; Department of Radiation Oncology, University Hospital Zurich, Zurich, Switzerland; Department of Radiation Oncology, Inselspital, Bern University Hospital, University of Bern, Switzerland
| | - S Safai
- Center for Proton Therapy, Paul Scherrer Institut, Villigen, Switzerland
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Davídková M, Ankjærgaard C, Andersen C, Dasu A, De Angelis C, De Marzi L, De Saint-Hubert M, Ekendahl D, Henthorn N, Michaelidesová AJ, Knežević Ž, Krzempek D, Kukolowicz P, Liszka M, Lorentini S, Leite AM, Majer M, Navrátil M, Reniers B, Ślusarczyk-Kacprzyk W, Van Goethem MJ, Vestergaard A, Vilches-Freixas G, Vondráček V, Togno M, Stolarczyk L, Olko P. MAILED DOSIMETRY AUDIT OF ACTIVE SCANNING PROTON BEAMS IN TEN PROTON THERAPY CENTERS. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)02370-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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Christensen JB, Togno M, Bossin L, Pakari OV, Safai S, Yukihara EG. Improved simultaneous LET and dose measurements in proton therapy. Sci Rep 2022; 12:8262. [PMID: 35585205 PMCID: PMC9117334 DOI: 10.1038/s41598-022-10575-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 04/11/2022] [Indexed: 11/23/2022] Open
Abstract
The objective of this study was to improve the precision of linear energy transfer (LET) measurements using \documentclass[12pt]{minimal}
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\begin{document}$$\text {Al}_2\text {O}_3\text {:C}$$\end{document}Al2O3:C optically stimulated luminescence detectors (OSLDs) in proton beams, and, with that, improve OSL dosimetry by correcting the readout for the LET-dependent ionization quenching. The OSLDs were irradiated in spot-scanning proton beams at different doses for fluence-averaged LET values in the (0.4–6.5) \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {keV}\, \upmu \hbox {m}^{-1}$$\end{document}keVμm-1 range (in water). A commercial automated OSL reader with a built-in beta source was used for the readouts, which enabled a reference irradiation and readout of each OSLD to establish individual corrections. Pulsed OSL was used to separately measure the blue (F-center) and UV (\documentclass[12pt]{minimal}
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\begin{document}$$F^+$$\end{document}F+-center) emission bands of \documentclass[12pt]{minimal}
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\begin{document}$$\text {Al}_2\text {O}_3\text {:C}$$\end{document}Al2O3:C and the ratio between them (UV/blue signal) was used for the LET measurements. The average deviation between the simulated and measured LET values along the central beam axis amounts to 5.5% if both the dose and LET are varied, but the average deviation is reduced to 3.5% if the OSLDs are irradiated with the same doses. With the measurement procedure and automated equipment used here, the variation in the signals used for LET estimates and quenching-corrections is reduced from 0.9 to 0.6%. The quenching-corrected OSLD doses are in agreement with ionization chamber measurements within the uncertainties. The automated OSLD corrections are demonstrated to improve the LET estimates and the ionization quenching-corrections in proton dosimetry for a clinically relevant energy range up to 230 MeV. It is also for the first time demonstrated how the LET can be estimated for different doses.
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Affiliation(s)
- Jeppe Brage Christensen
- Department of Radiation Safety and Security, Paul Scherrer Institute, Villigen PSI, Switzerland.
| | - Michele Togno
- Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Lily Bossin
- Department of Radiation Safety and Security, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Oskari Ville Pakari
- Department of Radiation Safety and Security, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Sairos Safai
- Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
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Ollivier J, Grilj V, Goncalves PJ, Petit B, Martinotti A, Barrera P, Psoroulas S, Nesteruk K, Meer D, Togno M, Safai S, Folkerts M, Pfister S, Sharma R, Lomax A, Weber D, Vozenin MC. IMPACT OF DOSE RATE DELIVERED WITH ELECTRON, PROTON AND PHOTON BEAMS ON THE DEVELOPMENT OF ZEBRAFISH EMBRYOS. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)01643-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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Yukihara E, Christensen J, Togno M. Demonstration of an optically stimulated luminescence (OSL) material with reduced quenching for proton therapy dosimetry: MgB4O7:Ce,Li. RADIAT MEAS 2022. [DOI: 10.1016/j.radmeas.2022.106721] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Togno M, Nesteruk K, Grossmann M, Dütschler A, Weber D, Lomax A, Meer D, Psoroulas S, Safai S. FLASH in the Clinic Track (Oral Presentations) ULTRA-HIGH DOSE RATE DOSIMETRY FOR PRE-CLINICAL EXPERIMENTS WITH MM-SMALL PROTON FIELDS. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)01505-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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Kacem H, Vozenin MC, Psoroulas S, Meer D, Safai S, Togno M, Lomax A, Weber D, Folkerts M, Pfister S, Sharma K. HYDROGEN PEROXIDE PRODUCTION AFTER IRRADIATION WITH PROTON BEAM AT VARIOUS DOSE RATES. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)01603-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Giovannelli AC, Maradia V, Meer D, Safai S, Psoroulas S, Togno M, Bula C, Weber DC, Lomax AJ, Fattori G. Beam properties within the momentum acceptance of a clinical gantry beamline for proton therapy. Med Phys 2022; 49:1417-1431. [PMID: 35041207 DOI: 10.1002/mp.15449] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 12/08/2021] [Accepted: 12/29/2021] [Indexed: 11/08/2022] Open
Abstract
PURPOSE Energy changes in Pencil Beam Scanning (PBS) proton therapy can be a limiting factor in delivery time, hence limiting patient throughput and the effectiveness of motion mitigation techniques requiring fast irradiation. In this study, we investigate the feasibility of performing fast and continuous energy modulation within the momentum acceptance of a clinical beamline for proton therapy. METHODS The alternative use of a local beam degrader at the gantry coupling point has been compared with a more common upstream regulation. Focusing on clinically relevant parameters, a complete beam properties characterization has been carried out. In particular, the acquired empirical data allowed to model and parametrize the errors in range and beam current to deliver clinical treatment plans. RESULTS For both options, the local and the upstream degrader, depth-dose curves measured in water for off-momentum beams were only marginally distorted (γ(1%,1mm) > 90%) and the errors in the spot position were within the clinical tolerance, even though increasing at the boundaries of the investigated scan range. The impact on the beam size was limited for the upstream degrader while dedicated strategies could be required to tackle the beam broadening through the local degrader. Range correction models were investigated for the upstream regulation. The impaired beam transport required a dedicated strategy for fine range control and compensation of beam intensity losses. Our current parametrization based on empirical data allowed energy modulation within acceptance with range errors (median 0.05 mm) and transmission (median -14%) compatible with clinical operation and remarkably low average 27 ms dead time for small energy changes. The technique, tested for the delivery of a skull glioma treatment, resulted in high gamma pass rates at 1%,1mm compared to conventional deliveries in experimental measurements with about 45% reduction of the energy switching time when regulation could be performed within acceptance. CONCLUSIONS Fast energy modulation within beamline acceptance has potential for clinical applications and, when realized with an upstream degrader, does not require modification in the beamline hardware, therefore being potentially applicable in any running facility. Centers with slow energy switching time can particularly profit from such a technique for reducing dead time during treatment delivery. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Anna Chiara Giovannelli
- Center for Proton Therapy, Paul Scherrer Institut, Switzerland.,Department of Physics, ETH Zürich, Switzerland
| | - Vivek Maradia
- Center for Proton Therapy, Paul Scherrer Institut, Switzerland.,Department of Physics, ETH Zürich, Switzerland
| | - David Meer
- Center for Proton Therapy, Paul Scherrer Institut, Switzerland
| | - Sairos Safai
- Center for Proton Therapy, Paul Scherrer Institut, Switzerland
| | | | - Michele Togno
- Center for Proton Therapy, Paul Scherrer Institut, Switzerland
| | - Christian Bula
- Center for Proton Therapy, Paul Scherrer Institut, Switzerland
| | - Damien Charles Weber
- Center for Proton Therapy, Paul Scherrer Institut, Switzerland.,University Hospital Zürich, Switzerland.,University Hospital Bern, University of Bern, Switzerland
| | - Antony John Lomax
- Center for Proton Therapy, Paul Scherrer Institut, Switzerland.,Department of Physics, ETH Zürich, Switzerland
| | - Giovanni Fattori
- Center for Proton Therapy, Paul Scherrer Institut, Switzerland.,Department of Physics, ETH Zürich, Switzerland
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Winterhalter C, Togno M, Nesteruk KP, Emert F, Psoroulas S, Vidal M, Meer D, Weber DC, Lomax A, Safai S. Faraday cup for commissioning and quality assurance for proton pencil beam scanning beams at conventional and ultra-high dose rates. Phys Med Biol 2021; 66. [PMID: 33906166 DOI: 10.1088/1361-6560/abfbf2] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 04/27/2021] [Indexed: 11/11/2022]
Abstract
Recently, proton therapy treatments delivered with ultra-high dose rates have been of high scientific interest, and the Faraday cup (FC) is a promising dosimetry tool for such experiments. Different institutes use different FC designs, and either a high voltage guard ring, or the combination of an electric and a magnetic field is employed to minimize the effect of secondary electrons. The authors first investigate these different approaches for beam energies of 70, 150, 230 and 250 MeV, magnetic fields between 0 and 24 mT and voltages between -1000 and 1000 V. When applying a magnetic field, the measured signal is independent of the guard ring voltage, indicating that this setting minimizes the effect of secondary electrons on the reading of the FC. Without magnetic field, applying the negative voltage however decreases the signal by an energy dependent factor up to 1.3% for the lowest energy tested and 0.4% for the highest energy, showing an energy dependent response. Next, the study demonstrates the application of the FC up to ultra-high dose rates. FC measurements with cyclotron currents up to 800 nA (dose rates of up to approximately 1000 Gy s-1) show that the FC is indeed dose rate independent. Then, the FC is applied to commission the primary gantry monitor for high dose rates. Finally, short-term reproducibility of the monitor calibration is quantified within single days, showing a standard deviation of 0.1% (one sigma). In conclusion, the FC is a promising, dose rate independent tool for dosimetry up to ultra-high dose rates. Caution is however necessary when using a FC without magnetic field, as a guard ring with high voltage alone can introduce an energy dependent signal offset.
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Affiliation(s)
- C Winterhalter
- Centre for Proton Therapy, Paul Scherrer Institute, Switzerland.,Physics Department, ETH Zurich, Switzerland
| | - M Togno
- Centre for Proton Therapy, Paul Scherrer Institute, Switzerland
| | - K P Nesteruk
- Centre for Proton Therapy, Paul Scherrer Institute, Switzerland
| | - F Emert
- Centre for Proton Therapy, Paul Scherrer Institute, Switzerland
| | - S Psoroulas
- Centre for Proton Therapy, Paul Scherrer Institute, Switzerland
| | - M Vidal
- Institut Mediterraneen de Protontherapie, Centre Antoine Lacassagne, Nice, France
| | - D Meer
- Centre for Proton Therapy, Paul Scherrer Institute, Switzerland
| | - D C Weber
- Centre for Proton Therapy, Paul Scherrer Institute, Switzerland.,Radiation Oncology Department of the University Hospital of Bern, Switzerland.,Radiation Oncology Department of the University Hospital of Zürich, Switzerland
| | - A Lomax
- Centre for Proton Therapy, Paul Scherrer Institute, Switzerland.,Physics Department, ETH Zurich, Switzerland
| | - S Safai
- Centre for Proton Therapy, Paul Scherrer Institute, Switzerland
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Nesteruk KP, Togno M, Grossmann M, Lomax AJ, Weber DC, Schippers JM, Safai S, Meer D, Psoroulas S. Commissioning of a clinical pencil beam scanning proton therapy unit for ultra-high dose rates (FLASH). Med Phys 2021; 48:4017-4026. [PMID: 33963576 DOI: 10.1002/mp.14933] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 04/04/2021] [Accepted: 04/27/2021] [Indexed: 12/26/2022] Open
Abstract
PURPOSE The purpose of this work was to provide a flexible platform for FLASH research with protons by adapting a former clinical pencil beam scanning gantry to irradiations with ultra-high dose rates. METHODS PSI Gantry 1 treated patients until December 2018. We optimized the beamline parameters to transport the 250 MeV beam extracted from the PSI COMET accelerator to the treatment room, maximizing the transmission of beam intensity to the sample. We characterized a dose monitor on the gantry to ensure good control of the dose, delivered in spot-scanning mode. We characterized the beam for different dose rates and field sizes for transmission irradiations. We explored scanning possibilities in order to enable conformal irradiations or transmission irradiations of large targets (with transverse scanning). RESULTS We achieved a transmission of 86% from the cyclotron to the treatment room. We reached a peak dose rate of 9000 Gy/s at 3 mm water equivalent depth, along the central axis of a single pencil beam. Field sizes of up to 5 × 5 mm2 were achieved for single-spot FLASH irradiations. Fast transverse scanning allowed to cover a field of 16 × 1.2 cm2 . With the use of a nozzle-mounted range shifter, we are able to span depths in water ranging from 19.6 to 37.9 cm. Various dose levels were delivered with precision within less than 1%. CONCLUSIONS We have realized a proton FLASH irradiation setup able to investigate continuously a wide dose rate spectrum, from 1 to 9000 Gy/s in single-spot irradiation as well as in the pencil beam scanning mode. As such, we have developed a versatile test bench for FLASH research.
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Affiliation(s)
- Konrad P Nesteruk
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland
| | - Michele Togno
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland
| | - Martin Grossmann
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland
| | - Anthony J Lomax
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.,Department of Physics, ETH Zurich, Zurich, Switzerland
| | - Damien C 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, Bern, Switzerland
| | - Jacobus M Schippers
- Division of Large Research Facilities, Paul Scherrer Institute, Villigen, Switzerland
| | - Sairos Safai
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland
| | - David Meer
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland
| | - Serena Psoroulas
- Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland
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17
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Christensen JB, Togno M, Nesteruk KP, Psoroulas S, Meer D, Weber DC, Lomax T, Yukihara EG, Safai S. Al 2O 3:C optically stimulated luminescence dosimeters (OSLDs) for ultra-high dose rate proton dosimetry. Phys Med Biol 2021; 66. [PMID: 33571973 DOI: 10.1088/1361-6560/abe554] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 02/11/2021] [Indexed: 11/11/2022]
Abstract
The response of Al2O3:C optically stimulated luminescence detectors (OSLDs) was investigated in a 250 MeV pencil proton beam. The OSLD response was mapped for a wide range of average dose rates up to 9000 Gy s-1, corresponding to a ∼150 kGy s-1instantaneous dose rate in each pulse. Two setups for ultra-high dose rate (FLASH) experiments are presented, which enable OSLDs or biological samples to be irradiated in either water-filled vials or cylinders. The OSLDs were found to be dose rate independent for all dose rates, with an average deviation <1% relative to the nominal dose for average dose rates of (1-1000) Gy s-1when irradiated in the two setups. A third setup for irradiations in a 9000 Gy s-1pencil beam is presented, where OSLDs are distributed in a 3 × 4 grid. Calculations of the signal averaging of the beam over the OSLDs were in agreement with the measured response at 9000 Gy s-1. Furthermore, a new method was presented to extract the beam spot size of narrow pencil beams, which is in agreement within a standard deviation with results derived from radiochromic films. The Al2O3:C OSLDs were found applicable to support radiobiological experiments in proton beams at ultra-high dose rates.
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Affiliation(s)
| | - Michele Togno
- Center for Proton Therapy, Paul Scherrer Institute, Switzerland
| | | | | | - David Meer
- Center for Proton Therapy, Paul Scherrer Institute, Switzerland
| | - Damien Charles Weber
- Center for Proton Therapy, Paul Scherrer Institute, Switzerland.,Department of Radiation Oncology, University Hospital Zurich, Switzerland.,Department of Radiation Oncology, University Hospital Bern, Switzerland
| | - Tony Lomax
- Center for Proton Therapy, Paul Scherrer Institute, Switzerland.,Department of Physics, ETH Zurich, Switzerland
| | - Eduardo G Yukihara
- Department of Radiation Safety and Security, Paul Scherrer Institute, Switzerland
| | - Sairos Safai
- Center for Proton Therapy, Paul Scherrer Institute, Switzerland
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Ozkan Loch C, Eichenberger MA, Togno M, Zinsli SP, Egloff M, Papa A, Ischebeck R, Lomax AJ, Peier P, Safai S. Characterization of a Low-Cost Plastic Fiber Array Detector for Proton Beam Dosimetry. Sensors (Basel) 2020; 20:s20205727. [PMID: 33050153 PMCID: PMC7601306 DOI: 10.3390/s20205727] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/21/2020] [Accepted: 09/28/2020] [Indexed: 01/12/2023]
Abstract
The Pencil Beam Scanning (PBS) technique in proton therapy uses fast magnets to scan the tumor volume rapidly. Changing the proton energy allows changing to layers in the third dimension, hence scanning the same volume several times. The PBS approach permits adapting the speed and/or current to modulate the delivered dose. We built a simple prototype that measures the dose distribution in a single step. The active detection material consists of a single layer of scintillating fibers (i.e., 1D) with an active length of 100 mm, a width of 18.25 mm, and an insignificant space (20 μm) between them. A commercial CMOS-based camera detects the scintillation light. Short exposure times allow running the camera at high frame rates, thus, monitoring the beam motion. A simple image processing method extracts the dose information from each fiber of the array. The prototype would allow scaling the concept to multiple layers read out by the same camera, such that the costs do not scale with the dimensions of the fiber array. Presented here are the characteristics of the prototype, studied under two modalities: spatial resolution, linearity, and energy dependence, characterized at the Center for Proton Therapy (Paul Scherrer Institute); the dose rate response, measured at an electron accelerator (Swiss Federal Institute of Metrology).
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Affiliation(s)
- Cigdem Ozkan Loch
- Department of Large Scale Research Facilities, Paul Scherrer Institut, 5232 Villigen, Switzerland; (M.A.E.); (S.P.Z.); (R.I.)
- Correspondence:
| | - Michael Alexander Eichenberger
- Department of Large Scale Research Facilities, Paul Scherrer Institut, 5232 Villigen, Switzerland; (M.A.E.); (S.P.Z.); (R.I.)
| | - Michele Togno
- Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen, Switzerland; (M.T.); (M.E.); (A.J.L.); (S.S.)
| | - Simon Pascal Zinsli
- Department of Large Scale Research Facilities, Paul Scherrer Institut, 5232 Villigen, Switzerland; (M.A.E.); (S.P.Z.); (R.I.)
| | - Martina Egloff
- Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen, Switzerland; (M.T.); (M.E.); (A.J.L.); (S.S.)
| | - Angela Papa
- Department for Research with Neutrons and Muons, Paul Scherrer Institut, 5232 Villigen, Switzerland;
| | - Rasmus Ischebeck
- Department of Large Scale Research Facilities, Paul Scherrer Institut, 5232 Villigen, Switzerland; (M.A.E.); (S.P.Z.); (R.I.)
| | - Antony John Lomax
- Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen, Switzerland; (M.T.); (M.E.); (A.J.L.); (S.S.)
| | - Peter Peier
- Laboratory Ionising Radiation, Federal Institute of Metrology (METAS), 3003 Bern-Wabern, Switzerland;
| | - Sairos Safai
- Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen, Switzerland; (M.T.); (M.E.); (A.J.L.); (S.S.)
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Fattori G, Hrbacek J, Regele H, Bula C, Mayor A, Danuser S, Oxley DC, Rechsteiner U, Grossmann M, Via R, Böhlen TT, Bolsi A, Walser M, Togno M, Colvill E, Lempen D, Weber DC, Lomax AJ, Safai S. Commissioning and quality assurance of a novel solution for respiratory-gated PBS proton therapy based on optical tracking of surface markers. Z Med Phys 2020; 32:52-62. [PMID: 32830006 PMCID: PMC9948868 DOI: 10.1016/j.zemedi.2020.07.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 06/01/2020] [Accepted: 07/10/2020] [Indexed: 12/15/2022]
Abstract
We present the commissioning and quality assurance of our clinical protocol for respiratory gating in pencil beam scanning proton therapy for cancer patients with moving targets. In a novel approach, optical tracking has been integrated in the therapy workflow and used to monitor respiratory motion from multiple surrogates, applied on the patients' chest. The gating system was tested under a variety of experimental conditions, specific to proton therapy, to evaluate reaction time and reproducibility of dose delivery control. The system proved to be precise in the application of beam gating and allowed the mitigation of dose distortions even for large (1.4cm) motion amplitudes, provided that adequate treatment windows were selected. The total delivered dose was not affected by the use of gating, with measured integral error within 0.15cGy. Analysing high-resolution images of proton transmission, we observed negligible discrepancies in the geometric location of the dose as a function of the treatment window, with gamma pass rate greater than 95% (2%/2mm) compared to stationary conditions. Similarly, pass rate for the latter metric at the 3%/3mm level was observed above 97% for clinical treatment fields, limiting residual movement to 3mm at end-exhale. These results were confirmed in realistic clinical conditions using an anthropomorphic breathing phantom, reporting a similarly high 3%/3mm pass rate, above 98% and 94%, for regular and irregular breathing, respectively. Finally, early results from periodic QA tests of the optical tracker have shown a reliable system, with small variance observed in static and dynamic measurements.
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Affiliation(s)
- Giovanni Fattori
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland.
| | - Jan Hrbacek
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Harald Regele
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Christian Bula
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Alexandre Mayor
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Stefan Danuser
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - David C. Oxley
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Urs Rechsteiner
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Martin Grossmann
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Riccardo Via
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Till T. Böhlen
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Alessandra Bolsi
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Marc Walser
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Michele Togno
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Emma Colvill
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Daniel Lempen
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Damien C. Weber
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland,Department of Radiation Oncology, University Hospital Zurich, 8091 Zurich, Switzerland,Department of Radiation Oncology, University Hospital Bern, 3000 Bern, Switzerland
| | - Antony J. Lomax
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland,Department of Physics, ETH Zurich, 8092 Zurich, Switzerland
| | - Sairos Safai
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen, Switzerland
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Vai A, Mirandola A, Magro G, Maestri D, Mastella E, Mairani A, Molinelli S, Russo S, Togno M, Civita SL, Ciocca M. Characterization of a MLIC Detector for QA in Scanned Proton and Carbon Ion Beams. Int J Part Ther 2020; 6:50-59. [PMID: 31998821 DOI: 10.14338/ijpt-19-00064.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 10/10/2019] [Indexed: 11/21/2022] Open
Abstract
Purpose Beam energy validation is a fundamental aspect of the routine quality assurance (QA) protocol of a particle therapy facility. A multilayer ionization chamber (MLIC) detector provides the optimal tradeoff between achieving accuracy in particle range determination and saving operational time in measurements and analysis procedures. We propose the characterization of a commercial MLIC as a suitable QA tool for a clinical environment with proton and carbon-ion scanning beams. Materials and Methods Commercial MLIC Giraffe (IBA Dosimetry, Schwarzenbruck, Germany) was primarily evaluated in terms of short-term and long-term stability, linearity with dose, and dose-rate independence. Accuracy was tested by analyzing range of integrated depth-dose curves for a set of representative energies against reference acquisitions in water for proton and carbon ion beams; in addition, 2 modulated proton spread-out Bragg peaks were also measured. Possible methods to increase the native spatial resolution of the detector were also investigated. Results Measurements showed a high repeatability: mean relative standard deviation was within 0.5% for all channels and both particle types. The long-term stability of the gain calibration showed discrepancies less than 1% at different times. The detector response was linear with dose (R 2 > 0.99) and independent on the dose rate. Measurements of integrated depth-dose curve ranges revealed a mean deviation from reference measurements in water of 0.1 ± 0.3 mm for protons with a maximum difference of 0.4 mm and 0.2 ± 0.6 mm with maximum difference of 0.85 mm for carbon ion beams. For the 2 modulated proton spread-out Bragg peaks, measured differences in distal dose falloff were ≤0.5 mm against calculated values. Conclusions The detector is stable, linearly responding with dose, precise, and easy to handle for QA beam energy checks of proton and carbon ion beams.
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Affiliation(s)
- Alessandro Vai
- Fondazione CNAO (Italian National Center for Oncological Hadronterapy), Pavia, Italy
| | - Alfredo Mirandola
- Fondazione CNAO (Italian National Center for Oncological Hadronterapy), Pavia, Italy
| | - Giuseppe Magro
- Fondazione CNAO (Italian National Center for Oncological Hadronterapy), Pavia, Italy
| | - Davide Maestri
- Fondazione CNAO (Italian National Center for Oncological Hadronterapy), Pavia, Italy
| | - Edoardo Mastella
- Fondazione CNAO (Italian National Center for Oncological Hadronterapy), Pavia, Italy
| | - Andrea Mairani
- Fondazione CNAO (Italian National Center for Oncological Hadronterapy), Pavia, Italy.,Heidelberg Ion-Beam Therapy Center, Heidelberg, Germany
| | - Silvia Molinelli
- Fondazione CNAO (Italian National Center for Oncological Hadronterapy), Pavia, Italy
| | - Stefania Russo
- Fondazione CNAO (Italian National Center for Oncological Hadronterapy), Pavia, Italy
| | - Michele Togno
- R&D Department, IBA Dosimetry, Schwarzenbruck, Germany
| | | | - Mario Ciocca
- Fondazione CNAO (Italian National Center for Oncological Hadronterapy), Pavia, Italy
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Vai A, Maestri D, Magro G, Mairani A, Mastella E, Mirandola A, Molinelli S, Russo S, Togno M, La Civita S, Ciocca M. PO-0894 Characterization of a multilayer ionization chamber for relative depth-dose curves in particle beams. Radiother Oncol 2019. [DOI: 10.1016/s0167-8140(19)31314-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Placidi L, Togno M, Weber DC, Lomax AJ, Hrbacek J. Range resolution and reproducibility of a dedicated phantom for proton PBS daily quality assurance. Z Med Phys 2018; 28:310-317. [DOI: 10.1016/j.zemedi.2018.02.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 02/13/2018] [Accepted: 02/13/2018] [Indexed: 10/17/2022]
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Togno M, Wilkens JJ, Menichelli D, Oechsner M, Perez-Andujar A, Morin O. Development and clinical evaluation of an ionization chamber array with 3.5 mm pixel pitch for quality assurance in advanced radiotherapy techniques. Med Phys 2017; 43:2283. [PMID: 27147340 DOI: 10.1118/1.4945414] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To characterize a new air vented ionization chamber technology, suitable to build detector arrays with small pixel pitch and independence of sensitivity on dose per pulse. METHODS The prototype under test is a linear array of air vented ionization chambers, consisting of 80 pixels with 3.5 mm pixel pitch distance and a sensitive volume of about 4 mm(3). The detector has been characterized with (60)Co radiation and MV x rays from different linear accelerators (with flattened and unflattened beam qualities). Sensitivity dependence on dose per pulse has been evaluated under MV x rays by changing both the source to detector distance and the beam quality. Bias voltage has been varied in order to evaluate the charge collection efficiency in the most critical conditions. Relative dose profiles have been measured for both flattened and unflattened distributions with different field sizes. The reference detectors were a commercial array of ionization chambers and an amorphous silicon flat panel in direct conversion configuration. Profiles of dose distribution have been measured also with intensity modulated radiation therapy (IMRT), stereotactic radiosurgery (SRS), and volumetric modulated arc therapy (VMAT) patient plans. Comparison has been done with a commercial diode array and with Gafchromic EBT3 films. RESULTS Repeatability and stability under continuous gamma irradiation are within 0.3%, in spite of low active volume and sensitivity (∼200 pC/Gy). Deviation from linearity is in the range [0.3%, -0.9%] for a dose of at least 20 cGy, while a worsening of linearity is observed below 10 cGy. Charge collection efficiency with 2.67 mGy/pulse is higher than 99%, leading to a ±0.9% sensitivity change in the range 0.09-2.67 mGy/pulse (covering all flattened and unflattened beam qualities). Tissue to phantom ratios show an agreement within 0.6% with the reference detector up to 34 cm depth. For field sizes in the range 2 × 2 to 15 × 15 cm(2), the output factors are in agreement with a thimble chamber within 2%, while with 25 × 25 cm(2) field size, an underestimation of 4.0% was found. Agreement of field and penumbra width measurements with the flat panel is of the order of 1 mm down to 1 × 1 cm(2) field size. Flatness and symmetry values measured with the 1D array and the reference detectors are comparable, and differences are always smaller than 1%. Angular dependence of the detector, when compared to measurements taken with a cylindrical chamber in the same phantom, is as large as 16%. This includes inhomogeneity and asymmetry of the design, which during plan verification are accounted for by the treatment planning system (TPS). The detector is capable to reproduce the dose distributions of IMRT and VMAT plans with a maximum deviation from TPS of 3.0% in the target region. In the case of VMAT and SRS plans, an average (maximum) deviation of the order of 1% (4%) from films has been measured. CONCLUSIONS The investigated technology appears to be useful both for Linac QA and patient plan verification, especially in treatments with steep dose gradients and nonuniform dose rates such as VMAT and SRS. Major limitations of the present prototype are the linearity at low dose, which can be solved by optimizing the readout electronics, and the underestimation of output factors with large field sizes. The latter problem is presently not completely understood and will require further investigations.
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Affiliation(s)
- M Togno
- Physik-Department, Technische Universität München, Munich 85748, Germany; Department of Radiation Oncology, Technische Universität München, Klinikum rechts der Isar, Munich 81675, Germany; and IBA Dosimetry GmbH, Schwarzenbruck 90592, Germany
| | - J J Wilkens
- Physik-Department, Technische Universität München, Munich 85748, Germany and Department of Radiation Oncology, Technische Universität München, Klinikum rechts der Isar, Munich 81675, Germany
| | - D Menichelli
- IBA Dosimetry GmbH, Schwarzenbruck 90592, Germany
| | - M Oechsner
- Department of Radiation Oncology, Technische Universität München, Klinikum rechts der Isar, Munich 81675, Germany
| | - A Perez-Andujar
- Department of Radiation Oncology, University of California, San Francisco, San Francisco, California 94143
| | - O Morin
- Department of Radiation Oncology, University of California, San Francisco, San Francisco, California 94143
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Togno M, Menichelli D, Vogel C, Celi J, Wilkens J, McGlade J, Mooij R, Olszanski A, Solberg T. EP-1497: High resolution air-vented ionization chamber array for QA of VMAT and stereotactic treatments. Radiother Oncol 2016. [DOI: 10.1016/s0167-8140(16)32747-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Togno M, Wilkens J, Menichelli D. SU-E-T-415: An Ionization Chamber Array with High Spatial Resolution for External Beam Radiotherapy. Med Phys 2014. [DOI: 10.1118/1.4888748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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