A Universal Range Shifter and Range Compensator Can Enable Proton Pencil Beam Scanning Single-Energy Bragg Peak FLASH-RT Treatment Using Current Commercially Available Proton Systems

Kang, Minglei; Wei, Shouyi; Choi, J. Isabelle; Lin, Haibo; Simone, Charles B.

doi:10.1016/j.ijrobp.2022.01.009

Cited by 38 publications

(70 citation statements)

References 41 publications

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“…In recent years, the field of radiation therapy (RT) has witnessed a reemergence of tremendous interest in the delivery of RT at ultrahigh dose rates (UHDRs), typically greater than 40 Gy/s, beginning with the publication of Favaudon et al 1 . This interest is sparked by a large body of preclinical results that suggest that such UHDR delivery yields comparable tumor control while substantially reducing normal tissue toxicity in in vivo animal models 1–20 . This differential response to radiation delivered at UHDR between tumor and normal tissue widens the therapeutic window and is dubbed by the FLASH effect 1 .…”

Section: Introductionmentioning

confidence: 99%

“…Due to the current technological limitation of slow energy‐layer switching, shoot‐through techniques are widely employed in the treatment planning of proton FLASH‐RT, compromising the dose conformity to some extent in exchange for the high dose rate delivery 14–16 . Recent studies are also investigating the so‐called Bragg peak FLASH‐RT technique, attempting to preserve the high dose conformity at UHDRs 17,18 …”

Section: Introductionmentioning

confidence: 99%

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A 2D strip ionization chamber array with high spatiotemporal resolution for proton pencil beam scanning FLASH radiotherapy

et al. 2022

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Purpose Experimental measurements of two‐dimensional (2D) dose rate distributions in proton pencil beam scanning (PBS) FLASH radiation therapy (RT) are currently lacking. In this study, we characterize a newly designed 2D strip‐segmented ionization chamber array (SICA) with high spatial and temporal resolution and demonstrate its applications in a modern proton PBS delivery system at both conventional and ultrahigh dose rates. Methods A dedicated research beamline of the Varian ProBeam system was employed to deliver a 250‐MeV proton PBS beam with nozzle currents up to 215 nA. In the research and clinical beamlines, the spatial, temporal, and dosimetric performances of the SICA were characterized and compared with measurements using parallel‐plate ion chambers (IBA PPC05 and PTW Advanced Markus chamber), a 2D scintillator camera (IBA Lynx), Gafchromic films (EBT‐XD), and a Faraday cup. A novel reconstruction approach was proposed to enable the measurement of 2D dose and dose rate distributions using such a strip‐type detector. Results The SICA demonstrated a position accuracy of 0.12 ± 0.02 mm at a 20‐kHz sampling rate (50 μs per event) and a linearity of R2 > 0.99 for both dose and dose rate with nozzle beam currents ranging from 1 to 215 nA. The 2D dose comparison to the film measurement resulted in a gamma passing rate of 99.8% (2 mm/2%). A measurement‐based proton PBS 2D FLASH dose rate distribution was compared to simulation results and showed a gamma passing rate of 97.3% (2 mm/2%). Conclusions The newly designed SICA demonstrated excellent spatial, temporal, and dosimetric performances and is well suited for commissioning, quality assurance, and a wide range of clinical applications in proton PBS clinical and FLASH‐RT.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A 2D strip ionization chamber array with high spatiotemporal resolution for proton pencil beam scanning FLASH radiotherapy

et al. 2022

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“…When choosing OARs in a conventional way and evaluating dose rate for different indications (e.g., lung) as done in Ref. [25], the expected results will be different.…”

Section: Discussionmentioning

confidence: 99%

“…23,24 Apart from the ridge filter, a recent study proposed a method of utilizing range shifters and range compensators to implement FLASH with only a single-energy Bragg peak (per field). 25 The main goal of this paper is to investigate the feasibility of two ridge filter designs for PBS-IMPT, as an alternative to the spot-line-layer scanning strategy. Our study puts emphasis on its potential use for FLASH-IMPT, capable of achieving high dose rate and reducing treatment time.…”

Section: Introductionmentioning

confidence: 99%

Design of static and dynamic ridge filters for FLASH–IMPT: A simulation study

2022

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Purpose This paper focused on the design and optimization of ridge filter–based intensity‐modulated proton therapy (IMPT), and its potential applications for FLASH. Differing from the standard pencil beam scanning (PBS) mode, no energy/layer switching is required and total treatment time can be shortened. Methods Unique dose‐influence matrices were generated as a proton beam traverses through slabs of different thicknesses (i.e., modulation by different layers). To establish the references for comparison, conventional IMPT plans (single field) were created using a large‐scale nonlinear solver. The spot weights from the reference IMPT plans were used as inputs for optimizing the design of ridge filters. Two designs were evaluated: model A (static) and model B (dynamic). The ridge filter designs were first verified (by GEANT4 simulation) in a water phantom and then in an H&N case. A direct comparison was made between the GEANT4 simulation results of two models and their respective references, with regard to plan quality, dose‐averaged dose rate, and total treatment time. Results In both the water phantom and the H&N case, two models are able to modulate dose distributions with high conformity, showing no significant difference relative to the reference plans. Dose rate–volume histograms suggest that in order to achieve a dose rate of 40 Gy/s over 90% PTV, the beam intensity needs to be 2.5 × 1011 protons/s for both models. For a fraction dose of 10 Gy, the total treatment time (including both irradiation time and dead time) can be shortened by a factor of 4.9 (model A) and 6.5 (model B), relative to the reference plans. Conclusion Two proposed designs (both static and dynamic) can be used for PBS–IMPT requiring no layer switching. They are promising candidates for FLASH‐IMPT capable of reducing treatment time and achieving high dose rates while maintaining dose conformity simultaneously.

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“…However, it has been demonstrated recently that FLASH dose-rates using single-energy Bragg-peaks are achievable using range shifters and inverse optimization. 53 …”

Section: Discussionmentioning

confidence: 99%

Single-fraction 34 Gy Lung Stereotactic Body Radiation Therapy Using Proton Transmission Beams: FLASH-dose Calculations and the Influence of Different Dose-rate Methods and Dose/Dose-rate Thresholds

Marlen

Verbakel

Slotman

et al. 2022

Advances in Radiation Oncology

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A Universal Range Shifter and Range Compensator Can Enable Proton Pencil Beam Scanning Single-Energy Bragg Peak FLASH-RT Treatment Using Current Commercially Available Proton Systems

Cited by 38 publications

References 41 publications

A 2D strip ionization chamber array with high spatiotemporal resolution for proton pencil beam scanning FLASH radiotherapy

A 2D strip ionization chamber array with high spatiotemporal resolution for proton pencil beam scanning FLASH radiotherapy

Design of static and dynamic ridge filters for FLASH–IMPT: A simulation study

Single-fraction 34 Gy Lung Stereotactic Body Radiation Therapy Using Proton Transmission Beams: FLASH-dose Calculations and the Influence of Different Dose-rate Methods and Dose/Dose-rate Thresholds

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