A digital phantom was created from a CT scan of a patient’s head and employed together with GATE 8.2 Monte Carlo modeling of a linear accelerator of nominal 6 MV energy to simulate an irradiation geometry for a typical tumor volume centrally within the brain region. Although simplistic in arrangement, this setup was considered appropriate to demonstrate the dose enhancements that may be expected for megavoltage external beam radiation therapy for nanoparticles (NP) of different elemental composition and concentration. Ag, Gd, Pt, Au and Bi were modeled in concentrations varying from 15 mg NP / gram tissue to 70 mg NP / gram tissue. The maximum Average Dose Enhancement Factor (ADEF) to the Gross Tumour Volume (GTV) observed was 3 % for 70 mg NP / gram tissue of Bi.