Purpose: The accurate delivery of electrons at FLASH-RT dose rates in radiobiological experiments require new dosimeters that are capable of accurately measuring the radiation dose delivered at >0.55 Gy per pulse (>100 Gy/s) in real-time. We investigate the use of the novel Hyperscint RP100 plastic dosimeter as a direct pulse counter.
Methods: A Varian 21EX clinac was converted to deliver 16 MeV electrons at FLASH-RT (100 Gy/s) dose rates. The linearity and reproducibility of the plastic scintillator at FLASH-RT dose rates was established by comparing with a pinpoint ionization chamber placed under 10 cm of solid water, where it acts as a relative dosimeter due to intense recombination effects. The plastic scintillator detector and to EBT-XD Gafchromic radiochromic film. were calibrated at conventional dose rates (1000 MU/min) and then irradiated at FLASH-RT Dose rate over a range of 3-20 Gy.
Results: The plastic dosimeter response tracked with relative ion chamber measurements within ≤1% over a wide range of delivered doses and dose rates, showing excellent response linearity and reproducibility. Plastic dosimeter dose measurements agreed with Gafchromic EBT-XD film measurements within ±4-6%. Most importantly, the plastic scintillator system was able to detect the number of pulses delivered by the linac directly, allowing for instant verification of proper delivery of FLASH-RT beams.
Conclusion: The plastic dosimeter was able to accurately measure the delivered radiation absorbed dose under characterization and biological experimental conditions, with a higher degree of reliability than conventional radiochromic film. Furthermore, it was shown to directly and accurately measure the number of pulses delivered in real time. This shows potential for use as a real-time in-vivo dosimeter during biological experiments, as well as potential clinical applications.
Funding Support, Disclosures, and Conflict of Interest: Francois Therriault-Proulx is the founder and CEO of Medscint, Inc. No financial support from Medscint was provided for this study.