Experimental validation of time-driven proton PBS FLASH delivery on a clinical proton therapy system
- 1Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, PL-31342, Poland
- 2Corresponding author.
Abstract
Background and purpose: Clinical proton pencil beam scanning systems use dose-driven delivery, limiting operation at ultra-high dose rates required for FLASH radiotherapy. Time-driven spot delivery, controlled by irradiation time rather than monitor chamber feedback, may enable FLASH operation. We implemented a non-clinical time-driven FLASH strategy on a clinical proton PBS system and experimentally validated its performance. Materials and methods: FLASH delivery was achieved by increasing beamline transmission through the energy-selection system and replacing dose-driven spot control with time-driven delivery in the Scanning Controller Diagnostic mode. Beam transmission was evaluated at gantry angle 0°. Depth-dose distributions, beam optics, scanning accuracy and uniform field generation were assessed for 228.4 MeV protons at gantry angles of 0°, 180° and 270°. Results: Opening the ESS divergence-limiting slits increased beamline transmission from 8% to 57%, resulting in approximately 273 nA at the isocentre (1.7 × 10 12 protons s −1 ) and an estimated peak on-axis average dose rate of 2.0 × 10 3 Gy s −1 . An 11 × 11 spot field delivered 25 Gy in approximately 0.6 s, corresponding to an average field dose rate of 42 Gy s −1 , with up to 90 Gy s −1 measured at higher doses. Proton range and Bragg peak width remained unchanged. Spot position deviations were below 0.5 mm, and uniform 4 × 4 cm 2 fields with <3% flatness were achieved. Conclusions: Time-driven delivery enables experimental proton PBS operation at UHDR while maintaining beam characteristics suitable for reproducible dosimetry and radiobiological studies, providing a practical and experimentally characterised platform for preclinical proton PBS FLASH research.
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BibTeX
@article{krzempek2026experimental,
title = {{Experimental validation of time-driven proton PBS FLASH delivery on a clinical proton therapy system}},
author = {Dawid Krzempek and Jan Gajewski and Hubert Jabłoński and Anna Spaleniak and Wiktor Komenda and Konrad Guguła and Michał Kamiński and Michał Hankiewicz and Tomasz Pasiecznik and Krzysztof Suder and Leszek Malinowski and Tomasz Nowak and Natalia Mojżeszek and Marta Bałamut and Paweł Rogalski and Renata Kopeć and Marzena Rydygier},
journal = {Physics and Imaging in Radiation Oncology},
year = {2026},
month = oct,
doi = {10.1016/j.phro.2026.101110},
url = {https://doi.org/10.1016/j.phro.2026.101110},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Experimental validation of time-driven proton PBS FLASH delivery on a clinical proton therapy system
AU - Dawid Krzempek
AU - Jan Gajewski
AU - Hubert Jabłoński
AU - Anna Spaleniak
AU - Wiktor Komenda
AU - Konrad Guguła
AU - Michał Kamiński
AU - Michał Hankiewicz
AU - Tomasz Pasiecznik
AU - Krzysztof Suder
AU - Leszek Malinowski
AU - Tomasz Nowak
AU - Natalia Mojżeszek
AU - Marta Bałamut
AU - Paweł Rogalski
AU - Renata Kopeć
AU - Marzena Rydygier
PY - 2026
DA - 2026/10/10
JO - Physics and Imaging in Radiation Oncology
DO - 10.1016/j.phro.2026.101110
UR - https://doi.org/10.1016/j.phro.2026.101110
AB - Background and purpose: Clinical proton pencil beam scanning systems use dose-driven delivery, limiting operation at ultra-high dose rates required for FLASH radiotherapy. Time-driven spot delivery, controlled by irradiation time rather than monitor chamber feedback, may enable FLASH operation. We implemented a non-clinical time-driven FLASH strategy on a clinical proton PBS system and experimentally validated its performance. Materials and methods: FLASH delivery was achieved by increasing beamline transmission through the energy-selection system and replacing dose-driven spot control with time-driven delivery in the Scanning Controller Diagnostic mode. Beam transmission was evaluated at gantry angle 0°. Depth-dose distributions, beam optics, scanning accuracy and uniform field generation were assessed for 228.4 MeV protons at gantry angles of 0°, 180° and 270°. Results: Opening the ESS divergence-limiting slits increased beamline transmission from 8% to 57%, resulting in approximately 273 nA at the isocentre (1.7 × 10 12 protons s −1 ) and an estimated peak on-axis average dose rate of 2.0 × 10 3 Gy s −1 . An 11 × 11 spot field delivered 25 Gy in approximately 0.6 s, corresponding to an average field dose rate of 42 Gy s −1 , with up to 90 Gy s −1 measured at higher doses. Proton range and Bragg peak width remained unchanged. Spot position deviations were below 0.5 mm, and uniform 4 × 4 cm 2 fields with <3% flatness were achieved. Conclusions: Time-driven delivery enables experimental proton PBS operation at UHDR while maintaining beam characteristics suitable for reproducible dosimetry and radiobiological studies, providing a practical and experimentally characterised platform for preclinical proton PBS FLASH research.
SN - 2405-6316
ER -