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Characterization of a Time-Resolved, Real-Time Scintillation Dosimetry System for Ultra-High Dose-Rate Radiation
Alexander Baikalov1, Daline Tho2, Kevin Liu3
1Department of Radiation Physics, University of Texas MD Anderson Cancer Center; Department of Radiation Oncology, School of Medicine and Klinikum rechts der Isar, Technical University of Munich, Munich, Germany; Institute of Radiation Medicine, Helmholtz Zentrum München GmbH, German Research Center for Environmental Health, Neuherberg, Germany.
Purpose:
Scintillation dosimetry has promising qualities for ultra-high-dose-rate (UHDR) radiation therapy (RT), but no system has shown compatibility with mean dose rates (DR¯) above 100 Gy/s and doses per pulse (Dp) exceeding 1.5 Gy typical of UHDR (FLASH)-RT. The aim of this study was to characterize a novel scintillation dosimetry system with the potential of accommodating UHDRs.
Methods And Materials:
We undertook a thorough dosimetric characterization of the system on an UHDR electron beamline. The system's response as a function of dose, DR¯, Dp, and the pulse dose-rate (DRp) was investigated, as was the system's dose sensitivity (signal per unit dose) as a function of dose history. The capabilities of the system for time-resolved dosimetric readout were also evaluated.
Results:
Within a tolerance of ±3%, the system exhibited dose linearity and was independent of DR¯ and Dp within the tested ranges of 1.8 to 1341 Gy/s and 0.005 to 7.68 Gy, respectively. A 6% reduction in the signal per unit dose was observed as DRp was increased from 8.9e4 to 1.8e6 Gy/s. The dose delivered per integration window of the continuously sampling photodetector had to remain between 0.028 and 11.56 Gy to preserve a stable signal response per unit dose. The system accurately measured Dp of individual pulses delivered at up to 120 Hz. The day-to-day variation of the signal per unit dose in a reference setup varied by up to ±13% but remained consistent (<±2%) within each treatment day and showed no signal loss as a function of dose history.
Conclusions:
With daily calibrations and DRp-specific correction factors, the system reliably provides real-time, millisecond-resolved dosimetric measurements of pulsed conventional and UHDR beams from typical electron linacs, marking an important advancement in UHDR dosimetry and offering diverse applications to FLASH-RT and related fields.
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