Estimation of Dose Perturbation Due to the Presence of Metal Hip Prostheses in Radiotherapy with Electron and Photon Beams: A Monte Carlo Study

Morteza  Hashemizadeh; Mansour  Zabihzadeh; Omid  Azadbakht; Masoud  Jamali

doi:10.18502/fbt.v11i4.16513

Morteza Hashemizadeh Department of Medical Physics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Mansour Zabihzadeh Department of Medical Physics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Omid Azadbakht Department of Radiology Technology, Behbahan Faculty of Medical Sciences, Behbahan, Iran
Masoud Jamali Radiation Oncologist, Technical Manager in Sarerm Hospital, Tehran, Iran

DOI: https://doi.org/10.18502/fbt.v11i4.16513

Keywords: Dose Perturbation; Electron Backscatter Factor; Hip Prostheses; Monte Carlo Calculation; Radiotherapy.

Abstract

Purpose: The impact of various hip prosthesis materials on the amount of dose perturbation generated by 9 MeV electron and 18 MV photon beams during pelvic radiation therapy is analyzed in this research.

Materials and Methods: The Varian 2100 C/D LINAC head for the electron (9 MeV) and photon (18 MV) modes and a water phantom with a realistic hip prosthesis were modeled using the Monte Carlo (MC) code; MCNPX (Ver. 2.6.0) and were benchmarked for measurement. Four different materials, including Cobalt–Chromium–Molybdenum-alloy (CCM), Stainless Steel (SS), Titanium, and Titanium-alloy (Ti-alloy) were evaluated. The changes in electron and photon fluences and dose perturbations due to the presence of the hip prostheses were investigated.

Results: An increased dose of 13.29%, 13.77%, 6.16%, and 5.93% for 9 MeV and 30.43%, 33.05%, 10.89%, and 11.27% for 18 MV was calculated for Ti-alloy, Ti, CCM, and SS prosthesis, respectively. At 0.5 mm distance from the prosthesis, the Electron Backscatter Factor (EBF) of 1.31, 1.33, 1.15, and 1.14 for 9 MeV and 1.32, 1.34, 1.11, and 1.12 for 18 MV was calculated for Ti-alloy, Ti, CCM, and SS prosthesis, respectively. Dose perturbation is higher at a near distance from the prosthesis; by reducing the distance from the Ti-alloy prosthesis (1.5 to 0.5 mm), an increased dose of 7.70% and 5.54% resulted in 18 MV and 9 MeV, respectively. The dose decreases of up to 21% behind the hip prosthesis were calculated for 18 MV.

Conclusion: It is essential to consider the dose perturbation due to the presence of a hip prosthesis to achieve the optimal treatment planning in radiotherapy.