Impact of Silicone gel breast prosthesis on photon beam therapy of recurrence carcinoma post mastectomy

AbstractIntroduction Silicone gel breast implants are used for breast reconstruction post mastectomy. In the event of cancer recurrence, the radiation oncologists are forced to irradiate through the prosthesis device. Due to prosthesis higher atomic number dose perturbations occur during treatment. This study determined the influence of silicone gel thickness on the photon beam distribution. Materials and MethodsA Varian linear accelerator, water phantom (dimensions 30 × 30 × 30 cm3), silicone gel breast prosthesis and Omni-Pro Accept software were used in the study. With the gantry positioned at at a source-to-surface distance (SSD) of 100 cm, the collimators were adjusted to a field size of 10 × 10 cm2 and the 6 MeV photon beam was used. Omni-Pro Accept software was used to plot the percentage depth dose curves and the beam profiles. The results obtained with a Monte Carlo Nuclear Particle (MCNP) Code were validated with the measurement data. The beam profile and percentage depth dose curves were also measured for silicone gel thicknesses (4, 6, 8, 10, 12, 14 and 16 cm) and width 16.5 cm aligned 1 cm below the surface of the water.ResultsThe measured and calculated percentage depth dose (PDD) ratio was 0.03. The measured and calculated beam profiles were 0.5% and 0.9% respectively. For the silicone gel prosthesis, the depth dose values at 0.5 cm below the prosthesis were 2.8%.ConclusionDose perturbations below the breast prosthesis are insignificant, breast prosthesis are safe in the event of carcinoma recurrences.

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Keywords: Monte Carlo method ، Silicone gel breast prosthesis ، Photon therapy ، Photon dose distribution ، MCNP code ، Percentage depth dose