(Sunday, 7/14/2019) 4:00 PM - 4:30 PM
Room: Exhibit Hall | Forum 4
Purpose: Gold nanoparticles (GNPs) have gained prominence in radiation therapy thanks to their unique radio-sensitizing properties. While sparing the surrounding healthy tissues, the presence of GNPs leads to dose amplification in their micrometric vicinity, due to low-energy photo and Auger electrons. The metric dose enhancement ratio (DER) is used, throughout the literature, to quantify GNPs efficacy to increase local energy deposition. However, there is a large disparity between the reported experimental radio-sensitization and the simulated values of DER for both diagnostic and therapeutic beams. The main objective of this study is to compare the profiles of DER in the vicinity of GNPs with another metric, RBE enhancement ratio (RBEER), in order to highlight the superiority of RBEER in predicting the radiobiological impact of GNPs.
Methods: In this work, Geant4 simulation toolkit has been used to obtain the DER and RBEER profiles around 10 and 20 nm GNPs for incident photons having energies of 120 kVp and 6 MV. The quantities of interest are tallied in 10 nm concentric spherical shells around GNP, and the resulting DER and RBEER profiles are plotted versus radial distance for each GNP size.
Results: In the diagnostic energy range, RBEER values are lower than DER in good agreement with the reported sensitization. Moreover, for therapeutic beams, the simulated values of RBEER are higher than DER in broad consistency with the literature, where it has been reported that the observed sensitization in the therapeutic range is higher than computational simulations.
Conclusion: The DER metric is not a good estimator of the radio-sensitization observed during in vivo or in vitro experiments, since the dose itself is a physical quantity. On the other hand, RBEER is a better predictor of the radiobiological outcome in GNP aided radiation therapy, due to its biological nature as compared with DER.
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