Comparing film measurements and Monte Carlo simulations of dose delivered in a pelvic phantom with titanium hip prosthesis

Abstract

An increasing number of elderly prostate cancer patients with high-density material hip prostheses are referred for external beam Radiotherapy (EBRT). Radiation treatment of pelvis cancer patients with high-density hip prostheses needs special attention due to the artifacts created in the computed tomography (CT) field of view and the radiotherapy dosimetry challenges. This study investigated the pelvic prostate point dose with and without titanium hip prosthesis using a 0.6 cc PTW Farmer ionization chamber, EBT3 Gafchromic films, compared with the EGSnrc Monte Carlo (MC) simulation dose distribution. The doses were measured and simulated in a locally made pelvic phantom. MC and measured doses were compared with the Treatment Planning System (TPS) calculated prostate point dose. The ionization chamber, EBT3 Gafchromic films, and MC doses have a maximum deviation of 6.3 %, 5.7 %, and 7.4 % for 6 MV and 4.2 %, 4.7 %, and 5.5 % for 15 MV photon beam, respectively, when compared with TPS calculated dose. There is a significant difference between the prostate point dose measured with ionization chamber, EBT3 Gafchromic film in comparison MC simulated doses. The MC simulation dose shows the highest deviation especially on the lateral field passing through the prosthesis.