Author: Dirk A Bartkoski, Michael Kleckner, Dongyeon Lee, Reza Reiazi, Mohammad Reza Salehpour π¨βπ¬
Affiliation: The University of Texas MD Anderson Cancer Center, Convergent-RnR π
Purpose:
To develop and validate G4BraggReflection, a novel physics process within Geant4, designed to incorporate diffraction properties resulting in Bragg reflection into Monte Carlo simulations. This process addresses critical challenges in modeling diffraction effects and crystal lattice interactions for both perfect and mosaic crystals, with applications in radiation therapy, particularly convergent radiotherapy.
Methods:
G4BraggReflection was implemented using a hybrid approach that combines Geant4βs particle tracking capabilities with solid-state physics principles. The model incorporates a mathematical framework to calculate reflection probabilities and mosaicity effects, enabling accurate simulations of Bragg reflection. Validation was performed against X-ray Oriented Programs (XOP) software by comparing reflectivity profiles for various energies, crystal configurations, and conditions. Key metrics, such as Ξ³-index and mean squared error (MSE), were evaluated to quantify the agreement between simulation and analytical results.
Results:
The G4BraggReflection process demonstrated excellent agreement with XOP. For mosaic crystals at 59.318 keV and 8 keV, Ξ³-indices reached 100% with MSE values as low as 1.41 Γ 10β»β΅. Perfect crystal simulations also showed strong agreement, with Ξ³-indices exceeding 93% for absorbing and nonabsorbing crystals. This high level of accuracy highlights the robustness of the process in modeling reflectivity under diverse conditions. The seamless integration into Geant4 enables simulations without toolkit recompilation, ensuring user-friendly application and adaptability.
Conclusion:
G4BraggReflection represents a groundbreaking advancement in Monte Carlo simulations, enabling precise modeling of Bragg reflection and bridging the gap between particle transport and wave-like quantum phenomena. This innovation provides support for developing converging radiotherapy techniques, offering the potential for highly focused and efficient cancer treatments with minimal damage to surrounding tissues. The development of this capability has allowed for exploration of novel radiotherapy devices including a focusing lens for xray capable producing therapeutic monoenergetic 60 keV xrays, demonstrating the processβs transformative impact on radiation oncology and its broader applications in applied physics and medical research.