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Bookbinder A, Selvaraj B, Zhao X, Yang Y, Bell BI, Pennock M, Tsai P, Tomé WA, Isabelle Choi J, Lin H, Simone CB, Guha C, Kang M. Validation and reproducibility of in vivo dosimetry for pencil beam scanned FLASH proton treatment in mice. Radiother Oncol 2024; 198:110404. [PMID: 38942121 DOI: 10.1016/j.radonc.2024.110404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 06/07/2024] [Accepted: 06/19/2024] [Indexed: 06/30/2024]
Abstract
PURPOSE To investigate quality assurance (QA) techniques for in vivo dosimetry and establish its routine uses for proton FLASH small animal experiments with a saturated monitor chamber. METHODS AND MATERIALS 227 mice were irradiated at FLASH or conventional (CONV) dose rates with a 250 MeV FLASH-capable proton beamline using pencil beam scanning to characterize the proton FLASH effect on abdominal irradiation and examining various endpoints. A 2D strip ionization chamber array (SICA) detector was positioned upstream of collimation and used for in vivo dose monitoring during irradiation. Before each irradiation series, SICA signal was correlated with the isocenter dose at each delivered dose rate. Dose, dose rate, and 2D dose distribution for each mouse were monitored with the SICA detector. RESULTS Calibration curves between the upstream SICA detector signal and the delivered dose at isocenter had good linearity with minimal R2 values of 0.991 (FLASH) and 0.985 (CONV), and slopes were consistent for each modality. After reassigning mice, standard deviations were less than 1.85 % (FLASH) and 0.83 % (CONV) for all dose levels, with no individual subject dose falling outside a ± 3.6 % range of the designated dose. FLASH fields had a field-averaged dose rate of 79.0 ± 0.8 Gy/s and mean local average dose rate of 160.6 ± 3.0 Gy/s. In vivo dosimetry allowed for the accurate detection of variation between the delivered and the planned dose. CONCLUSION In vivo dosimetry benefits FLASH experiments through enabling real-time dose and dose rate monitoring allowing mouse cohort regrouping when beam fluctuation causes delivered dose to vary from planned dose.
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Affiliation(s)
| | | | | | - Yunjie Yang
- New York Proton Center, New York, NY, USA; Departments of Radiation Oncology and Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Brett I Bell
- Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY, USA; Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Michael Pennock
- Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY, USA
| | - Pingfang Tsai
- New York Proton Center, New York, NY, USA; Departments of Radiation Oncology and Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Wolfgang A Tomé
- Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY, USA; Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, NY, USA
| | - J Isabelle Choi
- New York Proton Center, New York, NY, USA; Departments of Radiation Oncology and Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Haibo Lin
- New York Proton Center, New York, NY, USA; Departments of Radiation Oncology and Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY, USA
| | - Charles B Simone
- New York Proton Center, New York, NY, USA; Departments of Radiation Oncology and Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Chandan Guha
- Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY, USA; Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA; Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Minglei Kang
- New York Proton Center, New York, NY, USA; Departments of Radiation Oncology and Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
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Tsai P, Yang Y, Wu M, Chen C, Yu F, Simone CB, Choi JI, Tomé WA, Lin H. A comprehensive pre-clinical treatment quality assurance program using unique spot patterns for proton pencil beam scanning FLASH radiotherapy. J Appl Clin Med Phys 2024; 25:e14400. [PMID: 38831639 PMCID: PMC11302823 DOI: 10.1002/acm2.14400] [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: 01/03/2024] [Revised: 03/14/2024] [Accepted: 05/07/2024] [Indexed: 06/05/2024] Open
Abstract
BACKGROUND Quality assurance (QA) for ultra-high dose rate (UHDR) irradiation is a crucial aspect in the emerging field of FLASH radiotherapy (FLASH-RT). This innovative treatment approach delivers radiation at UHDR, demanding careful adoption of QA protocols and procedures. A comprehensive understanding of beam properties and dosimetry consistency is vital to ensure the safe and effective delivery of FLASH-RT. PURPOSE To develop a comprehensive pre-treatment QA program for cyclotron-based proton pencil beam scanning (PBS) FLASH-RT. Establish appropriate tolerances for QA items based on this study's outcomes and TG-224 recommendations. METHODS A 250 MeV proton spot pattern was designed and implemented using UHDR with a 215nA nozzle beam current. The QA pattern that covers a central uniform field area, various spot spacings, spot delivery modes and scanning directions, and enabling the assessment of absolute, relative and temporal dosimetry QA parameters. A strip ionization chamber array (SICA) and an Advanced Markus chamber were utilized in conjunction with a 2 cm polyethylene slab and a range (R80) verification wedge. The data have been monitored for over 3 months. RESULTS The relative dosimetries were compliant with TG-224. The variations of temporal dosimetry for scanning speed, spot dwell time, and spot transition time were within ± 1 mm/ms, ± 0.2 ms, and ± 0.2 ms, respectively. While the beam-to-beam absolute output on the same day reached up to 2.14%, the day-to-day variation was as high as 9.69%. High correlation between the absolute dose and dose rate fluctuations were identified. The dose rate of the central 5 × 5 cm2 field exhibited variations within 5% of the baseline value (155 Gy/s) during an experimental session. CONCLUSIONS A comprehensive QA program for FLASH-RT was developed and effectively assesses the performance of a UHDR delivery system. Establishing tolerances to unify standards and offering direction for future advancements in the evolving FLASH-RT field.
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Affiliation(s)
| | - Yunjie Yang
- Department of Radiation OncologyMemorial Sloan Kettering Cancer CenterNew YorkNew YorkUSA
| | - Mengjou Wu
- New York Proton CenterNew YorkNew YorkUSA
| | | | - Francis Yu
- New York Proton CenterNew YorkNew YorkUSA
| | | | | | - Wolfgang A. Tomé
- Department of Radiation OncologyMontefiore Medical Center and Albert Einstein College of MedicineBronxNew YorkUSA
| | - Haibo Lin
- New York Proton CenterNew YorkNew YorkUSA
- Department of Radiation OncologyMemorial Sloan Kettering Cancer CenterNew YorkNew YorkUSA
- Department of Radiation OncologyMontefiore Medical Center and Albert Einstein College of MedicineBronxNew YorkUSA
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Lin Y, Zhang H, Gu S, Shen L, Lv M, Zhang M, Chen Z. Proton beam spot size and position measurements using a multi-strip ionization chamber. Phys Med 2024; 123:103411. [PMID: 38906045 DOI: 10.1016/j.ejmp.2024.103411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 06/07/2024] [Accepted: 06/11/2024] [Indexed: 06/23/2024] Open
Abstract
PURPOSE To develop and characterize a large-area multi-strip ionization chamber (MSIC) for efficient measurement of proton beam spot size and position at a synchrotron-based proton therapy facility. METHODS AND MATERIALS A 420 mm x 320 mm MSIC was designed with 240 vertical strips and 180 horizontal strips at 1.75 mm pitch. The MSIC was characterized by irradiating a grid of proton spots across 17 energies from 73.5 MeV to 235 MeV and comparing to simultaneous measurements made with a reference Gafchromic EBT3 film. Beam profiles, spot sizes, and positions were analyzed. Short term measurement stability and sensitivity were evaluated. RESULTS Excellent agreement was demonstrated between the MSIC and EBT3 film for both spot size and position measurements. Spot sizes agreed within ± 0.18 mm for all energies tested. Measured beam spot positions agreed within ± 0.17 mm. The detector showed good short term measurement stability and low noise performance. CONCLUSION The large-area MSIC enables efficient and accurate proton beam spot characterization across the clinical energy range. The results indicate the MSIC is suitable for pencil beam scanning proton therapy commissioning and quality assurance applications requiring fast spot size and position quantification.
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Affiliation(s)
- Ye Lin
- Department of Particle Beam Applications, Shanghai Advanced Research Institute, Chinese Academy of Sciences, 201200 Shanghai, China.
| | - Haiqun Zhang
- Department of Particle Beam Applications, Shanghai Advanced Research Institute, Chinese Academy of Sciences, 201200 Shanghai, China
| | - Shuaizhe Gu
- Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Liren Shen
- Department of General Technology, Shanghai Advanced Research Institute, Chinese Academy of Sciences, 201200 Shanghai, China
| | - Ming Lv
- Department of Particle Beam Applications, Shanghai Advanced Research Institute, Chinese Academy of Sciences, 201200 Shanghai, China
| | - Manzhou Zhang
- Department of Particle Beam Applications, Shanghai Advanced Research Institute, Chinese Academy of Sciences, 201200 Shanghai, China
| | - Zhiling Chen
- Department of Particle Beam Applications, Shanghai Advanced Research Institute, Chinese Academy of Sciences, 201200 Shanghai, China
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Kanouta E, Bruza P, Johansen JG, Kristensen L, Sørensen BS, Poulsen PR. Two-dimensional time-resolved scintillating sheet monitoring of proton pencil beam scanning FLASH mouse irradiations. Med Phys 2024; 51:5119-5129. [PMID: 38569159 DOI: 10.1002/mp.17049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 03/14/2024] [Accepted: 03/20/2024] [Indexed: 04/05/2024] Open
Abstract
BACKGROUND Dosimetry in pre-clinical FLASH studies is essential for understanding the beam delivery conditions that trigger the FLASH effect. Resolving the spatial and temporal characteristics of proton pencil beam scanning (PBS) irradiations with ultra-high dose rates (UHDR) requires a detector with high spatial and temporal resolution. PURPOSE To implement a novel camera-based system for time-resolved two-dimensional (2D) monitoring and apply it in vivo during pre-clinical proton PBS mouse irradiations. METHODS Time-resolved 2D beam monitoring was performed with a scintillation imaging system consisting of a 1 mm thick transparent scintillating sheet, imaged by a CMOS camera. The sheet was placed in a water bath perpendicular to a horizontal PBS proton beam axis. The scintillation light was reflected through a system of mirrors and captured by the camera with 500 frames per second (fps) for UHDR and 4 fps for conventional dose rates. The raw images were background subtracted, geometrically transformed, flat field corrected, and spatially filtered. The system was used for 2D spot and field profile measurements and compared to radiochromic films. Furthermore, spot positions were measured for UHDR irradiations. The measured spot positions were compared to the planned positions and the relative instantaneous dose rate to equivalent fiber-coupled point scintillator measurements. For in vivo application, the scintillating sheet was placed 1 cm upstream the right hind leg of non-anaesthetized mice submerged in the water bath. The mouse leg and sheet were both placed in a 5 cm wide spread-out Bragg peak formed from the mono-energetic proton beam by a 2D range modulator. The mouse leg position within the field was identified for both conventional and FLASH irradiations. For the conventional irradiations, the mouse foot position was tracked throughout the beam delivery, which took place through repainting. For FLASH irradiations, the delivered spot positions and relative instantaneous dose rate were measured. RESULTS The pixel size was 0.1 mm for all measurements. The spot and field profiles measured with the scintillating sheet agreed with radiochromic films within 0.4 mm. The standard deviation between measured and planned spot positions was 0.26 mm and 0.35 mm in the horizontal and vertical direction, respectively. The measured relative instantaneous dose rate showed a linear relation with the fiber-coupled scintillator measurements. For in vivo use, the leg position within the field varied between mice, and leg movement up to 3 mm was detected during the prolonged conventional irradiations. CONCLUSIONS The scintillation imaging system allowed for monitoring of UHDR proton PBS delivery in vivo with 0.1 mm pixel size and 2 ms temporal resolution. The feasibility of instantaneous dose rate measurements was demonstrated, and the system was used for validation of the mouse leg position within the field.
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Affiliation(s)
- Eleni Kanouta
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Jacob Graversen Johansen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Line Kristensen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
- Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Brita Singers Sørensen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
- Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Per Rugaard Poulsen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
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Zhou S, Chen Q, Haefner J, Smith W, Darafsheh A, Zhao T, Harrison NA, Zhou J, Lin L, Lu W, Shen L, Jiang H, Zhang T. Proton 3D dose measurement with a multi-layer strip ionization chamber (MLSIC) device. Phys Med Biol 2024; 69:135010. [PMID: 38843812 DOI: 10.1088/1361-6560/ad550f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 06/06/2024] [Indexed: 06/27/2024]
Abstract
Objective. In current clinical practice for quality assurance (QA), intensity modulated proton therapy (IMPT) fields are verified by measuring planar dose distributions at one or a few selected depths in a phantom. A QA device that measures full 3D dose distributions at high spatiotemporal resolution would be highly beneficial for existing as well as emerging proton therapy techniques such as FLASH radiotherapy. Our objective is to demonstrate feasibility of 3D dose measurement for IMPT fields using a dedicated multi-layer strip ionization chamber (MLSIC) device.Approach.Our developed MLSIC comprises a total of 66 layers of strip ion chamber (IC) plates arranged, alternatively, in thexandydirection. The first two layers each has 128 channels in 2 mm spacing, and the following 64 layers each has 32/33 IC strips in 8 mm spacing which are interconnected every eight channels. A total of 768-channel IC signals are integrated and sampled at a speed of 6 kfps. The MLSIC has a total of 19.2 cm water equivalent thickness and is capable of measurement over a 25 × 25 cm2field size. A reconstruction algorithm is developed to reconstruct 3D dose distribution for each spot at all depths by considering a double-Gaussian-Cauchy-Lorentz model. The 3D dose distribution of each beam is obtained by summing all spots. The performance of our MLSIC is evaluated for a clinical pencil beam scanning (PBS) plan.Main results.The dose distributions for each proton spot can be successfully reconstructed from the ionization current measurement of the strip ICs at different depths, which can be further summed up to a 3D dose distribution for the beam. 3D Gamma Index analysis indicates acceptable agreement between the measured and expected dose distributions from simulation, Zebra and MatriXX.Significance.The dedicated MLSIC is the first pseudo-3D QA device that can measure 3D dose distribution in PBS proton fields spot-by-spot.
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Affiliation(s)
- Shuang Zhou
- Department of Radiation Oncology, Physics Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63108, United States of America
| | - Qinghao Chen
- Department of Radiation Oncology, Physics Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63108, United States of America
| | - Jonathan Haefner
- Department of Radiation Oncology, Physics Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63108, United States of America
| | - Winter Smith
- Department of Radiation Oncology, Physics Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63108, United States of America
| | - Arash Darafsheh
- Department of Radiation Oncology, Physics Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63108, United States of America
| | - Tianyu Zhao
- Department of Radiation Oncology, Physics Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63108, United States of America
| | | | - Jun Zhou
- Emory Proton Therapy Center, Atlanta, GA 30308, United States of America
| | - Liyong Lin
- Emory Proton Therapy Center, Atlanta, GA 30308, United States of America
| | - Weiguo Lu
- Unversity of Texas, Southwestern, Dallas, TX 75390, United States of America
| | - Liuxing Shen
- TetraImaging LLC, Maryland Heights, MO 63043, United States of America
| | - Hao Jiang
- TetraImaging LLC, Maryland Heights, MO 63043, United States of America
| | - Tiezhi Zhang
- Department of Radiation Oncology, Physics Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63108, United States of America
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Clark M, Harms J, Vasyltsiv R, Sloop A, Kozelka J, Simon B, Zhang R, Gladstone D, Bruza P. Quantitative, real-time scintillation imaging for experimental comparison of different dose and dose rate estimations in UHDR proton pencil beams. Med Phys 2024. [PMID: 38860497 DOI: 10.1002/mp.17247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 03/28/2024] [Accepted: 04/02/2024] [Indexed: 06/12/2024] Open
Abstract
BACKGROUND Ultra-high dose rate radiotherapy (UHDR-RT) has demonstrated normal tissue sparing capabilities, termed the FLASH effect; however, available dosimetry tools make it challenging to characterize the UHDR beams with sufficiently high concurrent spatial and temporal resolution. Novel dosimeters are needed for safe clinical implementation and improved understanding of the effect of UHDR-RT. PURPOSE Ultra-fast scintillation imaging has been shown to provide a unique tool for spatio-temporal dosimetry of conventional cyclotron pencil beam scanning (PBS) deliveries, indicating the potential use for characterization of UHDR PBS proton beams. The goal of this work is to introduce this novel concept and demonstrate its capabilities in recording high-resolution dose rate maps at FLASH-capable proton beam currents, as compared to log-based dose rate calculation, internally developed UHDR beam simulation, and a fast point detector (EDGE diode). METHODS The light response of a scintillator sheet located at isocenter and irradiated by PBS proton fields (40-210 nA, 250 MeV) was imaged by an ultra-fast iCMOS camera at 4.5-12 kHz sampling frequency. Camera sensor and image intensifier gain were optimized to maximize the dynamic range; the camera acquisition rate was also varied to evaluate the optimal sampling frequency. Large field delivery enabled flat field acquisition for evaluation of system response homogeneity. Image intensity was calibrated to dose with film and the recorded spatio-temporal data was compared to a PPC05 ion chamber, log-based reconstruction, and EDGE diode. Dose and dose rate linearity studies were performed to evaluate agreement under various beam conditions. Calculation of full-field mean and PBS dose rate maps were calculated to highlight the importance of high resolution, full-field information in UHDR studies. RESULTS Camera response was linear with dose (R2 = 0.997) and current (R22 = 0.98) in the range from 2-22 Gy and 40-210 nA, respectively, when compared to ion chamber readings. The deviation of total irradiation time calculated with the imaging system from the log file recordings decreased from 0.07% to 0.03% when imaging at 12 kfps versus 4.5 kfps. Planned and delivered spot positions agreed within 0.2 ± $\pm$ 0.1 mm and total irradiation time agreed within 0.2 ± $\pm$ 0.2 ms when compared with the log files, indicating the high concurrent spatial and temporal resolution. For all deliveries, the PBS dose rate measured at the diode location agreed between the imaging and the diode within 3% ± $\pm$ 2% and with the simulation within 5% ± $\pm$ 3% CONCLUSIONS: Full-field mapping of dose and dose rate is imperative for complete understanding of UHDR PBS proton dose delivery. The high linearity and various spatiotemporal metric reporting capabilities confirm the continued use of this camera system for UHDR beam characterization, especially for spatially resolved dose rate information.
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Affiliation(s)
- Megan Clark
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Joseph Harms
- Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Roman Vasyltsiv
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Austin Sloop
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | | | - Bill Simon
- Sun Nuclear Inc., Melbourne, Florida, USA
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - David Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
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Levin DS, Friedman PS, Ferretti C, Ristow N, Tecchio M, Litzenberg DW, Bashkirov V, Schulte R. A prototype scintillator real-time beam monitor for ultra-high dose rate radiotherapy. Med Phys 2024; 51:2905-2923. [PMID: 38456622 DOI: 10.1002/mp.17018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 02/24/2024] [Accepted: 02/26/2024] [Indexed: 03/09/2024] Open
Abstract
BACKGROUND FLASH Radiotherapy (RT) is an emergent cancer RT modality where an entire therapeutic dose is delivered at more than 1000 times higher dose rate than conventional RT. For clinical trials to be conducted safely, a precise and fast beam monitor that can generate out-of-tolerance beam interrupts is required. This paper describes the overall concept and provides results from a prototype ultra-fast, scintillator-based beam monitor for both proton and electron beam FLASH applications. PURPOSE A FLASH Beam Scintillator Monitor (FBSM) is being developed that employs a novel proprietary scintillator material. The FBSM has capabilities that conventional RT detector technologies are unable to simultaneously provide: (1) large area coverage; (2) a low mass profile; (3) a linear response over a broad dynamic range; (4) radiation hardness; (5) real-time analysis to provide an IEC-compliant fast beam-interrupt signal based on true two-dimensional beam imaging, radiation dosimetry and excellent spatial resolution. METHODS The FBSM uses a proprietary low mass, less than 0.5 mm water equivalent, non-hygroscopic, radiation tolerant scintillator material (designated HM: hybrid material) that is viewed by high frame rate CMOS cameras. Folded optics using mirrors enable a thin monitor profile of ∼10 cm. A field programmable gate array (FPGA) data acquisition system generates real-time analysis on a time scale appropriate to the FLASH RT beam modality: 100-1000 Hz for pulsed electrons and 10-20 kHz for quasi-continuous scanning proton pencil beams. An ion beam monitor served as the initial development platform for this work and was tested in low energy heavy-ion beams (86Kr+26 and protons). A prototype FBSM was fabricated and then tested in various radiation beams that included FLASH level dose per pulse electron beams, and a hospital RT clinic with electron beams. RESULTS Results presented in this report include image quality, response linearity, radiation hardness, spatial resolution, and real-time data processing. The HM scintillator was found to be highly radiation damage resistant. It exhibited a small 0.025%/kGy signal decrease from a 216 kGy cumulative dose resulting from continuous exposure for 15 min at a FLASH compatible dose rate of 237 Gy/s. Measurements of the signal amplitude versus beam fluence demonstrate linear response of the FBSM at FLASH compatible dose rates of >40 Gy/s. Comparison with commercial Gafchromic film indicates that the FBSM produces a high resolution 2D beam image and can reproduce a nearly identical beam profile, including primary beam tails. The spatial resolution was measured at 35-40 µm. Tests of the firmware beta version show successful operation at 20 000 Hz frame rate or 50 µs/frame, where the real-time analysis of the beam parameters is achieved in less than 1 µs. CONCLUSIONS The FBSM is designed to provide real-time beam profile monitoring over a large active area without significantly degrading the beam quality. A prototype device has been staged in particle beams at currents of single particles up to FLASH level dose rates, using both continuous ion beams and pulsed electron beams. Using a novel scintillator, beam profiling has been demonstrated for currents extending from single particles to 10 nA currents. Radiation damage is minimal and even under FLASH conditions would require ≥50 kGy of accumulated exposure in a single spot to result in a 1% decrease in signal output. Beam imaging is comparable to radiochromic films, and provides immediate images without hours of processing. Real-time data processing, taking less than 50 µs (combined data transfer and analysis times), has been implemented in firmware for 20 kHz frame rates for continuous proton beams.
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Affiliation(s)
- Daniel S Levin
- Department of Physics, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Claudio Ferretti
- Department of Physics, University of Michigan, Ann Arbor, Michigan, USA
| | - Nicholas Ristow
- Department of Physics, University of Michigan, Ann Arbor, Michigan, USA
| | - Monica Tecchio
- Department of Physics, University of Michigan, Ann Arbor, Michigan, USA
| | - Dale W Litzenberg
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan, USA
| | - Vladimir Bashkirov
- Division of Biomedical Engineering Sciences, Loma Linda University School of Medicine, Loma Linda, California, USA
| | - Reinhard Schulte
- Division of Biomedical Engineering Sciences, Loma Linda University School of Medicine, Loma Linda, California, USA
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Tsubouchi T, Beltran CJ, Yagi M, Hamatani N, Takashina M, Shimizu S, Kanai T, Furutani KM. Beam delivery characteristics of the Hitachi carbon ion scanning system at Osaka Heavy Ion Medical Accelerator in Kansai (HIMAK). Med Phys 2024; 51:2239-2250. [PMID: 37877590 DOI: 10.1002/mp.16791] [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: 06/04/2023] [Revised: 09/15/2023] [Accepted: 09/28/2023] [Indexed: 10/26/2023] Open
Abstract
BACKGROUND Using the pencil beam raster scanning method employed at most carbon beam treatment facilities, spots can be moved without interrupting the beam, allowing for the delivery of a dose between spots (move dose). This technique is also known as Dose-Driven-Continuous-Scanning (DDCS). To minimize its impact on HIMAK patient dosimetry, there's an upper limit to the move dose. Spots within a layer are grouped into sets, or "break points," allowing continuous irradiation. The beam is turned off when transitioning between sets or at the end of a treatment layer or spill. The control system beam-off is accomplished by turning off the RF Knockout (RFKO) extraction and after a brief delay the High Speed Steering Magnet (HSST) redirects the beam transport away from isocenter to a beam dump. PURPOSE The influence of the move dose and beam on/off control on the dose distribution and irradiation time was evaluated by measurements never before reported and modelled for Hitachi Carbon DDCS. METHOD We conducted fixed-point and scanning irradiation experiments at three different energies, both with and without breakpoints. For fixed-point irradiation, we utilized a 2D array detector and an oscilloscope to measure beam intensity over time. The oscilloscope data enabled us to confirm beam-off and beam-on timing due to breakpoints, as well as the relative timing of the RFKO signal, HSST signal, and dose monitor (DM) signals. From these measurements, we analyzed and modelled the temporal characteristics of the beam intensity. We also developed a model for the spot shape and amplitude at isocenter occurring after the beam-off signal which we called flap dose and its dependence on beam intensity. In the case of scanning irradiation, we measured move doses using the 2D array detector and compared these measurements with our model. RESULT We observed that the most dominant time variation of the beam intensity was at 1 kHz and its harmonic frequencies. Our findings revealed that the derived beam intensity cannot reach the preset beam intensity when each spot belongs to different breakpoints. The beam-off time due to breakpoints was approximately 100 ms, while the beam rise time and fall time (tdecay ) were remarkably fast, about 10 ms and 0.2 ms, respectively. Moreover, we measured the time lag (tdelay ) of approximately 0.2 ms between the RFKO and HSST signals. Since tdelay ≈ tdecay at HIMAK then the HSST is activated after the residual beam intensity, resulting in essentially zero flap dose at isocenter from the HSST. Our measurements of the move dose demonstrated excellent agreement with the modelled move dose. CONCLUSION We conducted the first move dose measurement for a Hitachi Carbon synchrotron, and our findings, considering beam on/off control details, indicate that Hitachi's carbon synchrotron provides a stable beam at HIMAK. Our work suggests that measuring both move dose and flap dose should be part of the commissioning process and possibly using our model in the Treatment Planning System (TPS) for new facilities with treatment delivery control systems with higher beam intensities and faster beam-off control.
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Affiliation(s)
- Toshiro Tsubouchi
- Department of Medical Physics, Osaka Heavy Ion Therapy Center, Osaka, Japan
| | - Chris J Beltran
- Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, Osaka, Japan
- Department of Radiation Oncology, Division of Medical Physics, Mayo Clinic, Jacksonville, Florida, USA
| | - Masashi Yagi
- Department of Medical Physics, Osaka Heavy Ion Therapy Center, Osaka, Japan
- Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Noriaki Hamatani
- Department of Medical Physics, Osaka Heavy Ion Therapy Center, Osaka, Japan
| | - Masaaki Takashina
- Department of Medical Physics, Osaka Heavy Ion Therapy Center, Osaka, Japan
| | - Shinichi Shimizu
- Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Tatsuaki Kanai
- Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Keith M Furutani
- Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, Osaka, Japan
- Department of Radiation Oncology, Division of Medical Physics, Mayo Clinic, Jacksonville, Florida, USA
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9
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Spruijt K, Mossahebi S, Lin H, Lee E, Kraus J, Dhabaan A, Poulsen P, Lowe M, Ayan A, Spiessens S, Godart J, Hoogeman M. Multi-institutional consensus on machine QA for isochronous cyclotron-based systems delivering ultra-high dose rate (FLASH) pencil beam scanning proton therapy in transmission mode. Med Phys 2024; 51:786-798. [PMID: 38103260 DOI: 10.1002/mp.16854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Revised: 10/07/2023] [Accepted: 10/31/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND The first clinical trials to assess the feasibility of FLASH radiotherapy in humans have started (FAST-01, FAST-02) and more trials are foreseen. To increase comparability between trials it is important to assure treatment quality and therefore establish a standard for machine quality assurance (QA). Currently, the AAPM TG-224 report is considered as the standard on machine QA for proton therapy, however, it was not intended to be used for ultra-high dose rate (UHDR) proton beams, which have gained interest due to the observation of the FLASH effect. PURPOSE The aim of this study is to find consensus on practical guidelines on machine QA for UHDR proton beams in transmission mode in terms of which QA is required, how they should be done, which detectors are suitable for UHDR machine QA, and what tolerance limits should be applied. METHODS A risk assessment to determine the gaps in the current standard for machine QA was performed by an international group of medical physicists. Based on that, practical guidelines on how to perform machine QA for UHDR proton beams were proposed. RESULTS The risk assessment clearly identified the need for additional guidance on temporal dosimetry, addressing dose rate (constancy), dose spillage, and scanning speed. In addition, several minor changes from AAPM TG-224 were identified; define required dose rate levels, the use of clinically relevant dose levels, and the use of adapted beam settings to minimize activation of detector and phantom materials or to avoid saturation effects of specific detectors. The final report was created based on discussions and consensus. CONCLUSIONS Consensus was reached on what QA is required for UHDR scanning proton beams in transmission mode for isochronous cyclotron-based systems and how they should be performed. However, the group discussions also showed that there is a lack of high temporal resolution detectors and sufficient QA data to set appropriate limits for some of the proposed QA procedures.
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Affiliation(s)
- Kees Spruijt
- HollandPTC, Delft, The Netherlands
- Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Sina Mossahebi
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Haibo Lin
- New York Proton Center, New York, New York, USA
| | - Eunsin Lee
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, Ohio, USA
| | - James Kraus
- Department of Radiation Oncology, University of Alabama-Birmingham, Birmingham, Alabama, USA
| | - Anees Dhabaan
- Department of Radiation Oncology, Emory University of Medicine, Atlanta, Georgia, USA
| | - Per Poulsen
- Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark and Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Matthew Lowe
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK
| | - Ahmet Ayan
- Department of Radiation Oncology, Ohio State University Medical Center, Columbus, Ohio, USA
| | - Sylvie Spiessens
- Varian, a Siemens Healthineers Company, Groot-Bijgaarden, Belgium
| | - Jeremy Godart
- HollandPTC, Delft, The Netherlands
- Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Mischa Hoogeman
- HollandPTC, Delft, The Netherlands
- Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, The Netherlands
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10
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Monaco V, Ali OH, Bersani D, Abujami M, Boscardin M, Cartiglia N, Betta GFD, Data E, Donetti M, Ferrero M, Ficorella F, Giordanengo S, Villarreal OAM, Milian FM, Mohammadian-Behbahani MR, Olivares DM, Pullia M, Tommasino F, Verroi E, Vignati A, Cirio R, Sacchi R. Performance of LGAD strip detectors for particle counting of therapeutic proton beams. Phys Med Biol 2023; 68:235009. [PMID: 37827167 DOI: 10.1088/1361-6560/ad02d5] [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: 06/04/2023] [Accepted: 10/12/2023] [Indexed: 10/14/2023]
Abstract
Objective. The performance of silicon detectors with moderate internal gain, named low-gain avalanche diodes (LGADs), was studied to investigate their capability to discriminate and count single beam particles at high fluxes, in view of future applications for beam characterization and on-line beam monitoring in proton therapy.Approach. Dedicated LGAD detectors with an active thickness of 55μm and segmented in 2 mm2strips were characterized at two Italian proton-therapy facilities, CNAO in Pavia and the Proton Therapy Center of Trento, with proton beams provided by a synchrotron and a cyclotron, respectively. Signals from single beam particles were discriminated against a threshold and counted. The number of proton pulses for fixed energies and different particle fluxes was compared with the charge collected by a compact ionization chamber, to infer the input particle rates.Main results. The counting inefficiency due to the overlap of nearby signals was less than 1% up to particle rates in one strip of 1 MHz, corresponding to a mean fluence rate on the strip of about 5 × 107p/(cm2·s). Count-loss correction algorithms based on the logic combination of signals from two neighboring strips allow to extend the maximum counting rate by one order of magnitude. The same algorithms give additional information on the fine time structure of the beam.Significance. The direct counting of the number of beam protons with segmented silicon detectors allows to overcome some limitations of gas detectors typically employed for beam characterization and beam monitoring in particle therapy, providing faster response times, higher sensitivity, and independence of the counts from the particle energy.
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Affiliation(s)
- Vincenzo Monaco
- Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino, Italy
- Istituto Nazionale di Fisica Nucleare, sezione di Torino, Italy
| | - Omar Hammad Ali
- Fondazione Bruno Kessler, Center for Sensors & Devices , Trento, Italy
| | - Davide Bersani
- Istituto Nazionale di Fisica Nucleare, sezione di Pisa, Italy
| | - Mohammed Abujami
- Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino, Italy
- Istituto Nazionale di Fisica Nucleare, sezione di Torino, Italy
| | - Maurizio Boscardin
- Fondazione Bruno Kessler, Center for Sensors & Devices , Trento, Italy
- Trento Institute for Fundamental Physics and Applications, Povo, Trento, Italy
| | | | - Gian Franco Dalla Betta
- Trento Institute for Fundamental Physics and Applications, Povo, Trento, Italy
- Università degli Studi di Trento, Trento, Italy
| | - Emanuele Data
- Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino, Italy
- Istituto Nazionale di Fisica Nucleare, sezione di Torino, Italy
| | - Marco Donetti
- CNAO, Centro Nazionale di Adroterapia Oncologica, Pavia, Italy
| | - Marco Ferrero
- Istituto Nazionale di Fisica Nucleare, sezione di Torino, Italy
| | | | | | | | - Felix Mas Milian
- Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino, Italy
- Istituto Nazionale di Fisica Nucleare, sezione di Torino, Italy
- Universidade Estadual de Santa Cruz, Department of Exact and Technological Sciences, Ilhéus, Brazil
| | | | - Diango Montalvan Olivares
- Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino, Italy
- Istituto Nazionale di Fisica Nucleare, sezione di Torino, Italy
| | - Marco Pullia
- CNAO, Centro Nazionale di Adroterapia Oncologica, Pavia, Italy
| | - Francesco Tommasino
- Trento Institute for Fundamental Physics and Applications, Povo, Trento, Italy
- Università degli Studi di Trento, Trento, Italy
| | - Enrico Verroi
- Trento Institute for Fundamental Physics and Applications, Povo, Trento, Italy
| | - Anna Vignati
- Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino, Italy
- Istituto Nazionale di Fisica Nucleare, sezione di Torino, Italy
| | - Roberto Cirio
- Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino, Italy
- Istituto Nazionale di Fisica Nucleare, sezione di Torino, Italy
| | - Roberto Sacchi
- Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino, Italy
- Istituto Nazionale di Fisica Nucleare, sezione di Torino, Italy
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11
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Siddique S, Ruda HE, Chow JCL. FLASH Radiotherapy and the Use of Radiation Dosimeters. Cancers (Basel) 2023; 15:3883. [PMID: 37568699 PMCID: PMC10417829 DOI: 10.3390/cancers15153883] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 07/27/2023] [Accepted: 07/27/2023] [Indexed: 08/13/2023] Open
Abstract
Radiotherapy (RT) using ultra-high dose rate (UHDR) radiation, known as FLASH RT, has shown promising results in reducing normal tissue toxicity while maintaining tumor control. However, implementing FLASH RT in clinical settings presents technical challenges, including limited depth penetration and complex treatment planning. Monte Carlo (MC) simulation is a valuable tool for dose calculation in RT and has been investigated for optimizing FLASH RT. Various MC codes, such as EGSnrc, DOSXYZnrc, and Geant4, have been used to simulate dose distributions and optimize treatment plans. Accurate dosimetry is essential for FLASH RT, and radiation detectors play a crucial role in measuring dose delivery. Solid-state detectors, including diamond detectors such as microDiamond, have demonstrated linear responses and good agreement with reference detectors in UHDR and ultra-high dose per pulse (UHDPP) ranges. Ionization chambers are commonly used for dose measurement, and advancements have been made to address their response nonlinearities at UHDPP. Studies have proposed new calculation methods and empirical models for ion recombination in ionization chambers to improve their accuracy in FLASH RT. Additionally, strip-segmented ionization chamber arrays have shown potential for the experimental measurement of dose rate distribution in proton pencil beam scanning. Radiochromic films, such as GafchromicTM EBT3, have been used for absolute dose measurement and to validate MC simulation results in high-energy X-rays, triggering the FLASH effect. These films have been utilized to characterize ionization chambers and measure off-axis and depth dose distributions in FLASH RT. In conclusion, MC simulation provides accurate dose calculation and optimization for FLASH RT, while radiation detectors, including diamond detectors, ionization chambers, and radiochromic films, offer valuable tools for dosimetry in UHDR environments. Further research is needed to refine treatment planning techniques and improve detector performance to facilitate the widespread implementation of FLASH RT, potentially revolutionizing cancer treatment.
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Affiliation(s)
- Sarkar Siddique
- Department of Physics, Toronto Metropolitan University, Toronto, ON M5B 2K3, Canada;
| | - Harry E. Ruda
- Centre of Advance Nanotechnology, Faculty of Applied Science and Engineering, University of Toronto, Toronto, ON M5S 3E4, Canada;
- Department of Materials Science and Engineering, University of Toronto, Toronto, ON M5S 3E4, Canada
| | - James C. L. Chow
- Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 1X6, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5T 1P5, Canada
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12
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Jang YJ, Yang TK, Kim JH, Jang HS, Jeong JH, Kim KB, Kim GB, Park SH, Choi SH. Development of a Real-Time Pixel Array-Type Detector for Ultrahigh Dose-Rate Beams. SENSORS (BASEL, SWITZERLAND) 2023; 23:4596. [PMID: 37430512 DOI: 10.3390/s23104596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 05/08/2023] [Accepted: 05/08/2023] [Indexed: 07/12/2023]
Abstract
Although research into ultrahigh dose-rate (UHDR) radiation therapy is ongoing, there is a significant lack of experimental measurements for two-dimensional (2D) dose-rate distributions. Additionally, conventional pixel-type detectors result in significant beam loss. In this study, we developed a pixel array-type detector with adjustable gaps and a data acquisition system to evaluate its effectiveness in measuring UHDR proton beams in real time. We measured a UHDR beam at the Korea Institute of Radiological and Medical Sciences using an MC-50 cyclotron, which produced a 45-MeV energy beam with a current range of 10-70 nA, to confirm the UHDR beam conditions. To minimize beam loss during measurement, we adjusted the gap and high voltage on the detector and determined the collection efficiency of the developed detector through Monte Carlo simulation and experimental measurements of the 2D dose-rate distribution. We also verified the accuracy of the real-time position measurement using the developed detector with a 226.29-MeV PBS beam at the National Cancer Center of the Republic of Korea. Our results indicate that, for a current of 70 nA with an energy beam of 45 MeV generated using the MC-50 cyclotron, the dose rate exceeded 300 Gy/s at the center of the beam, indicating UHDR conditions. Simulation and experimental measurements show that fixing the gap at 2 mm and the high voltage at 1000 V resulted in a less than 1% loss of collection efficiency when measuring UHDR beams. Furthermore, we achieved real-time measurements of the beam position with an accuracy of within 2% at five reference points. In conclusion, our study developed a beam monitoring system that can measure UHDR proton beams and confirmed the accuracy of the beam position and profile through real-time data transmission.
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Affiliation(s)
- Young Jae Jang
- Research Team of Radiological Physics & Engineering, Korea Institute of Radiological & Medical Sciences, Seoul 01812, Republic of Korea
- Department of Accelerator Science, Korea University, Sejong 30015, Republic of Korea
| | - Tae Keun Yang
- Research Team of Radiological Physics & Engineering, Korea Institute of Radiological & Medical Sciences, Seoul 01812, Republic of Korea
| | - Jeong Hwan Kim
- Research Team of Radiological Physics & Engineering, Korea Institute of Radiological & Medical Sciences, Seoul 01812, Republic of Korea
| | - Hong Suk Jang
- Research Team of Radiological Physics & Engineering, Korea Institute of Radiological & Medical Sciences, Seoul 01812, Republic of Korea
| | - Jong Hwi Jeong
- Center for ProtonTherapy, National Cancer Center, Goyang 10408, Republic of Korea
| | - Kum Bae Kim
- Research Team of Radiological Physics & Engineering, Korea Institute of Radiological & Medical Sciences, Seoul 01812, Republic of Korea
| | - Geun-Beom Kim
- Research Team of Radiological Physics & Engineering, Korea Institute of Radiological & Medical Sciences, Seoul 01812, Republic of Korea
| | - Seong Hee Park
- Department of Accelerator Science, Korea University, Sejong 30015, Republic of Korea
| | - Sang Hyoun Choi
- Research Team of Radiological Physics & Engineering, Korea Institute of Radiological & Medical Sciences, Seoul 01812, Republic of Korea
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13
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Clark M, Ding X, Zhao L, Pogue B, Gladstone D, Rahman M, Zhang R, Bruza P. Ultra-fast, high spatial resolution single-pulse scintillation imaging of synchrocyclotron pencil beam scanning proton delivery. Phys Med Biol 2023; 68:045016. [PMID: 36716492 PMCID: PMC9935801 DOI: 10.1088/1361-6560/acb753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 01/12/2023] [Accepted: 01/30/2023] [Indexed: 02/01/2023]
Abstract
Objective.To demonstrates the ability of an ultra-fast imaging system to measure high resolution spatial and temporal beam characteristics of a synchrocyclotron proton pencil beam scanning (PBS) system.Approach.An ultra-fast (1 kHz frame rate), intensified CMOS camera was triggered by a scintillation sheet coupled to a remote trigger unit for beam on detection. The camera was calibrated using the linear (R2> 0.9922) dose response of a single spot beam to varying currents. Film taken for the single spot beam was used to produce a scintillation intensity to absolute dose calibration.Main results. Spatial alignment was confirmed with the film, where thexandy-profiles of the single spot cumulative image agreed within 1 mm. A sample brain patient plan was analyzed to demonstrate dose and temporal accuracy for a clinically-relevant plan, through agreement within 1 mm to the planned and delivered spot locations. The cumulative dose agreed with the planned dose with a gamma passing rate of 97.5% (2 mm/3%, 10% dose threshold).Significance. This is the first system able to capture single-pulse spatial and temporal information for the unique pulse structure of a synchrocyclotron PBS systems at conventional dose rates, enabled by the ultra-fast sampling frame rate of this camera. This study indicates that, with continued camera development and testing, target applications in clinical and FLASH proton beam characterization and validation are possible.
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Affiliation(s)
| | - Xuanfeng Ding
- Beaumont Proton Therapy Center, Detroit, MI, United States of America
| | - Lewei Zhao
- Beaumont Proton Therapy Center, Detroit, MI, United States of America
| | - Brian Pogue
- University of Wisconsin-Madison, Madison, WI, United States of America
| | - David Gladstone
- Dartmouth College, NH, Lebanon
- Dartmouth Cancer Center, NH, Lebanon
| | | | - Rongxiao Zhang
- Dartmouth College, NH, Lebanon
- Dartmouth Cancer Center, NH, Lebanon
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14
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Kanouta E, Poulsen PR, Kertzscher G, Sitarz MK, Sørensen BS, Johansen JG. Time-resolved dose rate measurements in pencil beam scanning proton FLASH therapy with a fiber-coupled scintillator detector system. Med Phys 2022; 50:2450-2462. [PMID: 36508162 DOI: 10.1002/mp.16156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 11/08/2022] [Accepted: 11/30/2022] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The spatial and temporal dose rate distribution of pencil beam scanning (PBS) proton therapy is important in ultra-high dose rate (UHDR) or FLASH irradiations. Validation of the temporal structure of the dose rate is crucial for quality assurance and may be performed using detectors with high temporal resolution and large dynamic range. PURPOSE To provide time-resolved in vivo dose rate measurements using a scintillator-based detector during proton PBS pre-clinical mouse experiments with dose rates ranging from conventional to UHDR. METHODS All irradiations were performed at the entrance plateau of a 250 MeV PBS proton beam. A detector system with four fiber-coupled ZnSe:O inorganic scintillators and 20 μs temporal resolution was used for dose rate measurements. The system was first characterized in terms of precision and stem signal. The detector precision was determined through repeated irradiations with the same field. The stem signal contribution was quantified by irradiating two of the detector probes alongside a bare fiber (fiber without a coupled scintillator). Next, the detector system was calibrated against an ionization chamber (IC) with all four detector probes and the IC placed in a water bath at 2 cm depth. A scan pattern covering 9.6 × 9.6 cm was used. Multiple irradiations with different requested nozzle currents provided instantaneous dose rates at the detector positions in the range of 7-1270 Gy/s. The correspondence of the detector signal (in Volts) to the instantaneous dose rate (in Gy/s) was found. The instantaneous dose rate was calculated from the beam current and the spot-to-detector distance assuming a Gaussian beam profile at distances up to 8 mm from the spot. Afterwards, the calibrated system was used in vivo, in mouse experiments, where mouse legs were irradiated with a constant dose and varying field dose rates of 0.7-87.5 Gy/s. The instantaneous dose rate was measured for each delivered spot and the delivered dose was determined as the integrated instantaneous dose rate. The spot dose profile and PBS dose rate map were calculated. The dose contamination to neighbouring mice were measured together with the upper limit of the dose to the mouse body. RESULTS The detectors showed high precision with ≤0.4% fluctuations in the measured dose. The stem signal exceeded 10% for spots <5 mm from the optical fiber and >18 mm from the scintillator. It contributed up to 0.2% to the total dose, which was considered negligible. All four detectors showed a non-linear relation between signal and instantaneous dose rate, which was modelled with a polynomial response function. In the mouse experiments, the measured scintillator dose showed 1.8% fluctuations, independent of the field dose rate. The in vivo measured spot dose profile had tails that deviated from a Gaussian profile with measurable dose contributions from spots up to 85 mm from the detector. Neighbour mouse irradiation contributed ∼1% of the total mouse dose. The upper limit of the mouse body dose was 6% of the mouse leg dose. CONCLUSIONS A fiber-coupled inorganic scintillator-based detector system can provide high precision in vivo measurements of the instantaneous dose rate if correction for the non-linear dose rate dependency is applied.
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Affiliation(s)
- Eleni Kanouta
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Per Rugaard Poulsen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark.,Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
| | | | - Mateusz Krzysztof Sitarz
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Brita Singers Sørensen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark.,Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Jacob Graversen Johansen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark.,Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
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15
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Vozenin MC, Bourhis J, Durante M. Towards clinical translation of FLASH radiotherapy. Nat Rev Clin Oncol 2022; 19:791-803. [DOI: 10.1038/s41571-022-00697-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2022] [Indexed: 11/09/2022]
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