Dose distrubution evaluation of different dental implants on a real human dry-skull model for head and neck cancer radiotherapy

Objectives: In this study, the effect of different dental implant materials on dose distribution in head and neck cancer radiotherapy planning was investigated in a real human dry-skull taken from cadaver. Methods: The effect of Root-shaped Yttrium (Y) stabilized tetragonal Zr polycrystalline (Y-TZP), Titanium (Ti), Alumina (Al2O3) and polyether ether ketone (PEEK) dental implants on dose distribution was investigated by three different methods; Monte Carlo (MC) simulation, Eclipse Treatment Planning System's (TPS) Pencil Beam Convolution (PBC) algorithm and Thermoluminescence Dosimeter (TLD). The 6 MV photon beam simulation was performed for the Varian 2300 C/D linear accelerator using the EGSnrc based BEAMnrc MC Code. To perform MC simulation on skull phantom, phantom CT images with extended CT scale were imported to BEAMnrc/EGSnrc MC code via CTCREATE code. Results: According to the dose distribution measurement in dry skull, the calculated dose differences between PBC and MC algorithms were in the range of 0.6-4.5% whereas the dose difference between MC and TLD were in the range of 1,1-14.6% range depending on implant material. The PBC calculated dose increase difference range confirmed with TLD measurements was between 1.7% and 19.8%. The PBC algorithm could not fully determine the dose due to backscattering caused by dental implants. This is probably due to the limitations and shortcomings of the PBC algorithm. Conclusion: The maximum dose increase was observed for the Y-TZP dental implant material, which has the highest physical density. No significant dose increase was observed for the PEEK implant probably due to the low physical density of implants close to the physical density of water.