Dosimetry verification of in vitro radiotherapy dose via laser polishing of 3D-printed metallic implant surface

Abstract

Titanium alloys have been frequently used for medical implants. However, their presence can cause variability in radiation dose during radiotherapy, leading to potential complications. Herein, this work aims to explore the impact of 3D printed Ti6Al4V implants on the dose of 6MV X-ray in radiotherapy, through direct measurement in the ionization chamber. The findings indicate that the absorption effect of titanium alloy implants lowers the dose behind the implants, while the backscattering effect increases the dose in front of the implants. It is demonstrated that the size, thickness, and mesh density of the titanium alloy implant show no significant effect on the dose in front of the implants. Nonetheless, it is found that the dose behind the implants increases with mesh density and decreases with implant thickness. Laser polishing is implemented as a surface modification technique for titanium implants, resulting in significantly improved implant surface smoothness, a reduction of the surface roughness, a decrease in defects and an alteration in the elemental composition percentage. Furthermore, the reduction in surface roughness leads to a transition towards a hydrophilic implant surface, which also leads to the enhancement of specular reflection and the reduction of diffuse scattering on the implant surface, thus producing a complex influence on the radiation dose. It is also revealed that at a constant X-ray irradiation energy, the dose values in front of and behind the implant both exhibit a declining trend as the irradiation field size increases. Finally, the existence of a dose compensation effect of scattered radiation on the primary radiation during radiotherapy is confirmed. This work provides important reference for clinical practice, aiding medical professionals in formulating precise treatment plans, optimizing the efficacy of radiotherapy, and minimizing side effects.