Verification of dose and dose rate for quality assurance of spread‐out‐Bragg‐peak proton FLASH radiotherapy using machine log files

• DOI: 10.1002/mp.17792
• Publication Date: 2025-04-04T04:20:18Z
• Authors: Seyyedeh Azar Oli...; François Vander S...; Michele M. Kim; Rudi Labarbe; Lucian Hotoiu; Arnaud Pin; Rasmus Nilsson; Erik Traneus; Keith A. Cengel; Wei Zou; Boon‐Keng Kevin Teo; Lei Dong; Eric S. Diffenderfer
• Keywords: Sobp; Pencil-beam scanning

Ultra-high dose rate radiotherapy elicits a biological effect (FLASH), which has been shown to reduce toxicity while maintaining tumor control in preclinical radiobiology experiments. FLASH depends on the rate, with evidence that higher rates drive increased normal tissue sparing. The pattern of delivery also significance for conformal proton delivered via pencil beam scanning (PBS) given its unique spatio-temporal distribution deposition. In PBS, machine-generated log file contains information PBS measured by segmented ionization chambers treatment nozzle. spot position and monitor unit (MU) obtained from files have previously used reconstruct Monte Carlo (MC) simulations. incorporation timing allows reconstruction 3D temporal distribution. log-based can role quality assurance (QA) verification if be accurate spatial domains Thus, objective this study is validate accuracy using input data machine delivery. By analyzing timing, position, MU extracted logs, we aim evaluate reliability precision reconstruction. spread-out Bragg peak (SOBP) fields were cyclotron accelerated beam. This method involves patient field-specific energy modulator (CEM) achieve SOBP at site. Log record positions 250 µs resolution. To information, 9.9 mm diameter parallel plate chamber was positioned various locations within SOBP. An electrometer sampling 20 kHz recorded time-resolved current collected chamber. These measurements determine dose, duration, transition times. Disparities between logged map determined. Dose average compared measurement MC There good agreement dwell time across detector positions. median disparities inter-spot range -0.041 0.024 ms. Differences planned are minimal, measuring less than 1.08 x direction 1.15 y direction, consistent prior studies resolution nozzle Delivered 1.9% MU. Measured simulated outcomes derived simulation. We validated through findings support use calculations as one part patient-specific (PSQA)