Room: Davidson Ballroom A
Purpose: To investigate the radiosensitization ability of FePt nanoparticle clusters (NPCs) and dose enhancement ratio (DER) under kilovoltage photons with Geant4 Monte Carlo method.
Methods: The Hela cells were incubated with FePt NPs and the distribution of NPCs were then obtained by optical microscope and X-ray Nano-CT imaging. DER was defined as the ratio of the energy deposited in the volume of interest between with and without the NPsC. Based on experimental images, a simplified cell model was developed to evaluate the DER of two types of NPCs (Fe1Pt1 and Fe1Pt3). For each type, the dependency of DER on the thickness and angular distribution of NPCs on the surface of the cell membrane was studied quantitatively.
Results: For each nanoparticles type, DER demonstrates an initial increase to a peak followed by gradual saturation. The peak occurs around 800 nm for 60 kVp. While for 150 kVp and 200 kVp, the saturation starts at a thickness of 1400 nm. Secondly, DER is strongly dependent on the photon energy and the distance from the NPCs to the nucleus. Lower photon energy results in a higher DER. Fe1Pt3 is able to achieve a higher DER relative to Fe1Pt1. For Fe1Pt3, the peak of DER is 64.52 (60 kVp), 41.32 (150 kVp ) and 39.21 (200 kVp), respectively.
Conclusion: The dependency of DER on a number of parameters was obtained, such as photon energy, two materials (Fe1Pt3 and Fe1Pt1), and the thickness of clusters. For a given photon energy, the trapping effect causes DER to saturate as the thickness of NPsC increases above a certain threshold. From the results in this paper, the potential use of FePt NPs as radiosensitizers under kilovoltage may be useful for cancers within superficial tissues, such as melanoma.