engleski

Development Of A Pregnant Female Phantom And Calculation Of Fetal Dose During A Photon Breast Radiotherapy

Purpose/Introduction The incidence of carcinoma during pregnancy is reported to be 1:1000 – 1:1500 pregnancies, and it has increased over the last 30 years. Breast carcinoma is the most common malignant tumor diagnosed during pregnancy. Within this study a model of the pregnant female, in her second trimester of pregnancy, is developed. It that can be used for radiotherapy treatment planning (as DICOM data), Monte Carlo simulations (as voxelized geometry) and for experimental dosimetry using 3D printing of the molds (as STL files). As a proof of concept, the phantom was used for fetal dose estimation during a photon breast radiotherapy plan. Materials/Methods The developed phantom is based on an MRI and CT images of a female patient in her 18th week of pregnancy. For the treatment of a left breast carcinoma 3D conformational radiotherapy was used. Beam energy was 6 MeV and the prescribed dose was 50 Gy in 25 fractions. The voxelized geometry of the phantom was used for Monte Carlo (MC) simulations using MCNP code in which all radiotherapy fields were simulated independently to determine both the breast target dose and fetal dose. Results Phantom was developed in such a manner that pregnant female and her fetus were scanned “in vivo” using MRI during pregnancy and CT after childbirth. The modelled photon breast radiotherapy plan, applied to the phantom, indicated that the fetus dose is 59 mGy for 50 Gy prescribed to the breast. The results clearly indicate that only 9.5 % of the photons reaching the fetus are generated in accelerator head through scatter and leakage, but the dominant component is scattered radiation from the patient’s body. Discussion The study offers the possibility to perform treatment planning, Monte Carlo simulations and physical measurements on a pregnant female phantom which is important for the improvement of current dosimetry practices in clinics. Our feasibility study demonstrated that the dose received by the fetus, during photon breast radiotherapy was just above the recommendation level which demonstrates the need to have good dosimetry tools in place for dose assessment and optimization

pregnacy ; phantom, Monte Carlo

nije evidentirano