TRANSMISSION PROTON THERAPY FOR SKULL-BASE TUMORS: ON-LINE POSITIONAL VERIFICATION AND ENHANCED ROBUSTNESS

Le résumé fourni par la source

Background and Aims: Ultra-high dose rate (FLASH) therapy offers the advantage of delivering therapeutic doses in 1-2 sessions.However, accurate dosimetry remains challenging because conventional ionization chambers suffer uncertainties from ion recombination and reduced ion-collection efficiency at FLASH.Alanine/ESR dosimetry provides a promising alternative, offering high accuracy, near-tissue equivalence, and minimal dependence on dose rate or beam energy.For reliable FLASH dose verification, establishing robust ESR-dose calibration curve is essential.In this study, alanine dosimeters were irradiated using both conventional and FLASH carbon-ion beams, and the corresponding ESR-dose response curves were obtained and compared.Methods: Alanine pellets were irradiated in the same beam an adjacent Advanced Markus ionization chamber using an AEC Twin Jabara water phantom at the Gunma University Heavy Ion Medical Center (GHMC).Conventional and FLASH carbon-ion beams were delivered with dose rates of 0.09 Gy/s and 174-265 Gy/s, respectively.Irradiation was performed in 10 Gy increments from 10 Gy to 100 Gy, and the alanine dosimeters were positioned at the center of the spread-out Bragg peak region based on uniform physical dose.Results: The calibration curve established under conventional carbon-ion beam conditions exhibited excellent linearity (R² = 0.9998) with dose deviations within 2%.However, when this conventional calibration was applied to alanine irradiated under FLASH conditions, substantial discrepancies were observed-dose errors reached up to 28.6% at low doses and 3-4% at higher doses.These deviations highlight the influence of the unique physical and chemical interactions induced by high-LET carbon ions at ultra-high dose rates.To address this, a FLASH-specific calibration curve was developed, showing similarly high linearity (R² = 0.9998) and improved dose deviations within 1.31%.Conclusions: This study demonstrates that conventional calibration curves are not directly applicable to FLASH carbon-ion beams due to significant response deviations.Establishing FLASH-specific ESR-dose response curves is therefore essential for accurate dose assessment, confirming alanine/ESR dosimetry as a reliable and robust tool for beam quality assurance in FLASH carbon-ion therapy.This work was supported by the Korea Hydro & Nuclear Power Co., LTD (No. 2023-Tech-11) and conducted as part of a research project on heavy ions at GHMC.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.