Author: Dirk A Bartkoski, Leonard Che Fru, Benjamin Abraham Insley, Michael Kleckner, Dongyeon Lee, Reza Reiazi, Mohammad Reza Salehpour, Aviad Schori, Ramesh C. Tailor 👨🔬
Affiliation: Empyrean Medical Systems, The University of Texas MD Anderson Cancer Center, Convergent-RnR, The University of Texas, MD Anderson, Houston TX 🌍
Purpose: A Geant4-based model was created for a G4BraggReflection process to simulate radiation transport within a novel radiotherapy system developed by Convergent Radiotherapy and Radiosurgery (CRnR; Hafia, Israel). This novel treatment device incorporates a Bragg-diffraction X-ray lens to focus diverging beams of X-rays from a conventional X-ray tube towards a small but finite focal spot at depth in tissue with quasi-monoenergetic photons.
Methods: The simulation code includes an X-ray tube generator and CRnR focusing lens consisting of aluminum crystals. To validate the Geant4 model of this device, transverse and longitudinal dose distributions of the converging X-ray field were calculated and compared to radiochromic film measurements.
Results: The Monte Carlo (MC) simulated transverse dose distributions indicated that the implemented system successfully converged the diverging X-ray beam into a single beam focal spot by following Bragg diffraction physics. The 2D dose distribution calculated along the converging beam’s longitudinal axis agrees well with film measurement. Furthermore, quasi-monoenergetic photons were observed at the focal spot position by the Bragg diffraction from the aluminum crystal lens in agreement with focal spot spectral measurements.
Conclusion:
In this study, CRnR’s converging beam radiotherapy system was modeled in Geant4 to validate the device operation and evaluate its physical and diametrical properties in the future. The MC simulation implemented in this work successfully demonstrated converging dose distributions with Bragg-diffraction physics, which were in excellent agreement with radiochromic film measurements. This simulation code can be used to further refine the converging beam system design for clinical implementation.