Design and validation of an integrated reference dosimetry and monitoring system for ultra-high dose-rate proton beams ranging from 20 Gy/s to 230 Gy/s

Purpose:

This study aims to design, develop, and test an integrated reference dosimetry and beam monitoring system tailored for proton beams in a dose rate regime ranging from 20 Gy/s to 230 Gy/s. The primary objective is to establish a robust system for diagnostic and dosimetry addressing the challenges associated with ultra-high dose-rate (UHDR) radiotherapy. The proposed detectors chain seeks to ensure accurate dose measurements to support future clinical applications and radiobiological experiments in FLASH proton therapy (pFLASH-RT).

Methods:

The system integrates three detectors, a Secondary Emission Monitor (SEM), a Dual-Gap Ionization Chamber (DGIC), and a Faraday Cup (FC) , providing dose measurements. The SEM and DGIC operate continuously to monitor dose rates, while the FC, designed with innovative geometric and electronic features, ensures dose calibration. Experimental validations were conducted using a 62 MeV proton beam at the INFN-LNS, spanning various dose rates. Calibration procedures and correction algorithms, including the Boag–Wilson theory, were applied to ensure the reliability of the dosimetry and monitoring system.

Results:

Experimental results demonstrated high reproducibility and accuracy of the entire system. The FC exhibited a mean relative dose uncertainty of 2%, with no significant response variation across dose rates, even at the highest dose rate tested (230 Gy/s). Similarly, the SEM demonstrated consistent performance, with an average agreement within 1.4% of the FC measurements. Additionally, the application of correction factors based on collection efficiency parameters reduced the DGIC measurement uncertainty to less than 3%.

Conclusion:

The proposed system represents a reliable solution for the dosimetry of UHDR proton beams. Its ability to provide accurate, real-time dose measurements under extreme beam conditions supports the integration of pFLASH-RT into clinical practice. While the individual detectors employed in this work (Faraday Cup, DGIC, SEM) are based on established technologies, the innovation of this study lies in the integration and cross-calibration of these components within a single real-time dosimetric architecture, experimentally validated over a wide dose rate range. Furthermore, the system’s robustness and reproducibility make it an invaluable tool for advancing radiobiological research and ensuring the safe application of UHDR proton therapy.