Fig. 2:

(a) Simulation results of participant G1 for dose per fluence in 10 nm-thick spherical shells at different radial distances from a 100 nm gold nanoparticle (GNP) irradiated in water with a circular 50 kVp photon beam of diameter 110 nm (symbols). The x-axis shows the difference between the radius of the spherical shell’s outer surface and the GNP radius and is linear up to 1000 nm and then logarithmic. The dashed blue lines on all panels indicate the value obtained without GNP for charged particle equilibrium (CPE); the solid blue lines mark the dose per fluence of primary particles for the case of full secondary particle equilibrium (SPE), i.e. including scattered photons. (b) Difference of the simulation results in (a) for the GNP present and absent (downward triangles) and corrected values taking into account scattered photons (circles). (c) Sums of the data shown in (b) and the constant values of dose to water per fluence for CPE and SPE.