Speaker
Description
This work presents the realization and complete characterization of a low energy electron mini-beam flash beam. This beam can vary the Flash parameters (Dose per pulse, average dose rate, intra-pulse dose rate) and the mini-beam parameters (Peak-to-Valley Dose Ratio (PVDR), FWHM and center-to-center (ctc) distance) independently from one and another. We utilize the Triode-Gun equipped ElectronFlash linac by SIT at the Centro Pisano FLASH Radiotherapy (CPFR), thanks to special funding from Fondazione Pisa, operating at 7 and 9 MeV with an average dose rate of up to 5,000 Gy/s. The linac's flexibility enables the independent variation of main parameters without altering the experimental setup.
To create Ultra-High Dose Rate (UHDR) mini-beams, Monte Carlo simulations are employed to design collimator templates, utilizing tungsten for its high atomic number to prevent electron bleed-through. Various hole structures and ctc in the templates are explored to study different mini-beam effects. Spatial distribution comparisons are conducted using radiochromic gafchromic films and three independent Monte Carlo simulation codes (EGSnrc, Geant4, and FLUKA). Despite inherent limitations in dose reading accuracy, the radiochromic films demonstrate agreement with Monte Carlo simulations.
The results highlight minor discrepancies in valley dose among Monte Carlo codes and generally falling within the uncertainty range of gafchromic films. Manipulating ctc influences valley dose, PVDR (above 30 in some configurations), and mini-beam zone size, providing versatility for different experimental setups. The proposed mini-beam generation method, combined with flash capabilities, establishes a robust platform for quantitative experiments, allowing the independent variation of spatial and temporal parameters. The mini-beam and mini-beam-flash operating beams emerge as valuable tools for radiobiological experiments, offering insights into quantitative dependencies and underlying mechanisms. This research contributes to advancing a comprehensive understanding of these novel techniques and their potential application in radiotherapy, providing a foundation for future clinical protocols and treatment planning systems.
