Author: Rafael Carballeira, David J. Gladstone, Philippe Liger, Rongxiao Zhang 👨🔬
Affiliation: TheryQ, Dartmouth College, University of Missouri, Thayer School of Engineering, Dartmouth College 🌍
Purpose: To model a FLASH electron beam system (FLASHLAB) via first principle Monte Carlo methods, navigating installation configurations, shielding and regulatory radiation safety considerations for ultra high dose rate (UHDR) irradiation at 7 MeV.
Methods: A detailed geometric model of the TheryQ FLASHLAB setup was created in GAMOS 6.2.0, incorporating an aluminum enclosure, collimator, exit window, and a surrounding “Room” volume. Parameterized voxel volumes were used to evaluate dose deposition in air regions or phantom‐like materials, and a 7 MeV point electron source was positioned upstream of the collimator. Simulations included electromagnetic physics processes relevant to electron interactions. To assess beam propagation and radiation leakage, phase‐space scorers and dose scorers were implemented, allowing visualization of the electron beam path, dose mapping within the enclosure, and potential dose contributions in the surrounding environment.
Results: Preliminary simulations confirmed that the electron beam travels as expected through the enclosure and collimator, depositing a measurable dose within the intended target region. Phase‐space data illustrated the energy and angular spread of electrons exiting the collimator, aiding in the identification of potential leakage paths. Dose values in the “Room” region remained below thresholds relevant for occupational exposure when the enclosure was modeled with sufficient shielding thickness. Data also indicated minimal secondary scattering beyond the primary field, suggesting that the chosen layout effectively confines high‐energy electrons and secondary x-rays.
Conclusion: This study demonstrates that a GAMOS‐based approach can accurately predict shielding performance for a FLASH electron beam facility. The resulting dose distributions and phase‐space analyses confirm that the modeled enclosure design maintains acceptable radiation safety margins while delivering FLASH therapy. Future work will refine material definitions and incorporate heterogeneous phantoms to optimize shielding and further validate dose accuracy for clinical or research applications.