Author: Ruirui Dong, Gernot Echner, Peter Haering, Clarence King, Carlos Murillo, Gavin Poludniowski, Nicholas Sammut, Joao Seco, Steffen Seeber, Maria Francesca Spadea, Elpida Theodoridou 👨🔬
Affiliation: KIT, Department of Physics and Astronomy, Heidelberg University, Karolinska Institutet, DKFZ, University of Malta 🌍
Purpose:
The goal is to develop the first benchtop X-ray FLASH system based on a conventional small animal irradiator. The small animal irradiator will be modeled using a Monte Carlo toolkit for both filtered and unfiltered X-rays at conventional dose rates of about 2Gy/min. The model will be based on dosimetric measurements taken at distances ranging from 13.1cm to 58.1cm from the source.
Methods:
Monte Carlo simulations were performed using the BEAMnrc code and the SpekPy toolkit to model the X-ray source under different operating conditions. Experimental validation was performed using ionization chambers and radiochromic films to measure radiation doses. Dose rate assessment was performed for both filtered and unfiltered beams, corresponding to X-ray tube energies of 119kV, 160kV, and 200kV. The experimental setup was carefully calibrated according to the TRS-398 protocol and correction factors were applied to account for the unfiltered beam characteristics. Inventor 2024 was used for the 3D design of the FLASH table-top platform system. Initial clonogenic assays were performed using normoxic protocols.
Results:
Monte Carlo simulations of dose rates at various distances showed a variation of about 5% compared to experimental measurements for filtered configurations. The strong consistency of these measurements subsequently suggested correction factors for the unfiltered beam measurements. HVL measurements showed strong agreement between experimental data and MC simulations, with discrepancies of less than 5%. Simulations demonstrated the potential to achieve FLASH conditions at 5 cm from the source, where the dose of 66Gy/s was achieved. An easily transferable FLASH system was designed that could be applied to any commercial X-ray source.
Conclusion:
The first benchtop X-ray FLASH system was modeled with EGSnrc and calibrated dosimetrically for use in-vitro and in-vivo. Preliminary in vitro studies were performed as an initial test of the X-ray FLASH system, with dose rates varying between 40Gy/s and 66Gy/s.