Milestone 1.5: Effects of LET on radio-sensitising effects of nanoparticles, comparison
with GEANT4 simulations
Marios Sotiropoulos – ESR3 – WP1
The gold nanoparticle radio-sensitization effect has been studied through Geant4 simulation. In the
simulation, a gold nanoparticles of 25 nm has been irradiated with 3, 25, and 100 MeV protons, which
corresponds to LET values of 11.7, 2.2, and 0.73 keV/μm respectively. The radial dose distribution,
which is the dose deposited in concentric spherical shells, and the dose enhancement ratio, which is
the dose deposited from a gold nanoparticle to the dose deposited by a virtual nanoparticle made from
water were calculated as an index of the radio-sensitization effect.
Our results based on the dose distributions and enhancement ratio predict a maximum enhancement
increase of about 15 fold for the low LET protons and a 9 fold maximum increase for the high LET
protons (Figure 1). Although the dose enhancement ratio provides useful information about the radiosensitization potential, does not incorporate important parameters such as the gold nanoparticle
distribution and DNA damage predicting substantially increased enhancement than experimentally
observed. Therefore, to fully understand the radio-sensitization effect at the cellular level a cell model
with detailed DNA structure has been created. Further investigation of the radio-sensitization effect in
terms of DNA damage is on the way.
100
DER
3 MeV; 11.7 keV/μm
25 MeV; 2.2 keV/μm
100 MeV; 0.73 keV/μm
10
1
1
10
100
1000 10000 100000 1000000
R (nm)
Figure 1. Dose enhancement ratio (DER) calculated by Geant4 simulations for a 25 nm gold nanoparticle
irradiated with 3, 25, and 100 MeV protons (LET values 11.7, 2.2, 0.73 keV/μm). Data adapted from
Sotiropoulos et al (2017).
The dose enhancement data, alongside with a sensitivity analysis on the Geant4 model used for the
calculation, have been published in Sotiropoulos et al (2017). Preliminary findings on the cell model
have been presented in Sotiropoulos et al (2016).
References
Sotiropoulos et al, 2016, Modelling DNA damage on gold nanoparticle enhanced proton therapy,
PPRIG Proton Therapy Physics Workshop 2016, National Physical Laboratory, Teddington, UK
Sotiropoulos et al, 2017, Biomed. Phys. Eng. Express, at press: https://doi.org/10.1088/20571976/aa69cc