Avaliação da influência dosimétrica dos implantes dentários de titânio em VMAT de cabeça e pescoço

Abstract

The head and neck cancer is more prevalent in men, predominantly middle or elderly age, featuring a group of individuals with high probability of having done osseointegrated dental implants. Most of these implants are made of titanium and the interaction of X-ray photons with this high atomic number material and high electron density generates scattering and disturbance on radiation dose in their interfaces, generating dosimetric uncertainties in the head and neck radiotherapy treatments. The aim of this study is to assess the dosimetric impact of dental implants of titanium in head and neck VMAT. For this, irradiation of phantom was performed in the presence of a titanium dental implant for direct field and with application of CShape Easy and Head and Neck tests proposed by the TG 119, adapted to VMAT. The planning of these cases was conducted according to criteria determined by the AAPM, with Monaco 5.0 software, and the treatment is in Linear Accelerator Synergy Elekta. The measurements were performed with Semiflex ionization chamber and electrometer US PTW, radiochromic film GafChromic EBT3 scanned with the Epson Expression XL scanner and analysis with the software VeriSoft 6.0. The results of the distribution and dose profiles found in direct irradiation field show that the presence of titanium dental implant causes significant dose disturbance. Due to the presence of the material was also increased the difference between the calculated and the measured dose when compared to irradiation of the homogeneous phantom. But in the dosimetry of TG 119 cases this difference was irrelevant. The dose calculated by the software and the measure with the ionization chamber had negligible differences, as well as the consent of the gamma criterion for cases with and without the presence of dental titanium implant. The results are satisfactory and consistent with other author’s tests in homogeneous phantoms. The impact of dental titanium implant presence can be minimized through the manual delimitation of the metal object and artifact generated and by assigning the electron density values corrected them, and include them as organs with dose constraints on optimization planning. From the testing CShape Easy and Head and Neck TG 119 of the AAPM, we have verified that following the recommendations described, the planning system Monaco 5.0 is capable of performing dose calculations with high degree of accuracy for head and neck VMAT in patients with titanium dental implant.