FETAL DOSE ESTIMATION DURING PREGNANCY USING GATE MONTE CARLO SIMULATION: APPLICATION OF HODGKIN'S LYMPHOMA RADIOTHERAPY.

The aim of this study is to estimate the fetal radiation dose for a pregnant patient treated for Hodgkin's lymphoma. Due to the supradiaphragmatic extensions, two plans are used for this treatment, one for supra-clavicular and the other for cervical lymph nodes, with beam energies of 18 and 6 MV, respectively. We model the ELEKTA accelerator (Versa HD Ltd, Crawly, UK) and the pregnant patient using GATE code. The accelerator is modelled based on the vendor-supplied data and the pregnant patient is modeled with a voxelized pregnant woman phantom (Katja, 29 years old) at the 24th week of pregnancy. In each plan, we estimate the absorbed dose of each fetus organ by delivering a 2 Gy for one fraction and then multiplying the result by 15 fractions to get the total prescribed dose, then we calculate the mean fetal absorbed dose. The results indicate that the mean absorbed fetal dose was 26.18 mGy.