Fig. 2

Comparison of predicted and observed values of dose enhancement for gold nanoparticles at both megavoltage and kilovoltage energies. “Increase in physical dose” here refers to the ratio of the additional dose deposited by X-rays in the system due to the addition of GNPs to that which would be deposited in the absence of gold. The observed data in this figure are dose modification results from in vitro experiments, while the predicted dose increase is based on the gold concentrations and X-ray energies used. The dashed line shows the trend which would be followed if the sensitizer enhancement ratio directly followed predicted increases in physical dose (Butterworth et al. 2013)