Characterizing devices for validation of dose, dose rate, and LET in ultra high dose rate proton irradiations

This study presents a methodology to validate dose, dose rate (DR), and linear energy transfer (LET) in ultra high dose rate (UHDR) proton therapy, also known as conformal FLASH. FLASH aims to reduce normal tissue damage while preserving tumor control, but its clinical use is limited by challenges in quality assurance (QA) measurements. Researchers used a 250-MeV proton beam and a 3D-printed ridge filter to deliver conformal FLASH to a spherical target. Dose and DR were measured using a 4D multi-layer strip ionization chamber (MLSIC), while LET was assessed using a high-resolution Timepix3 detector with an under-sample and recover (USRe) technique to avoid pile-up. Results from these measurements were compared with those from the MatriXX PT detector and Monte Carlo simulations. The data showed high agreement between experimental results and simulations, with >95% gamma passing rates for dose comparisons and <0.3% difference in DR at the lateral margins. LET measurements also showed strong alignment, with Bhattacharyya distances <1.3% across margins. The study concludes that this methodology is effective for experimental validation and QA of FLASH treatment plans.

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