Modeling and dosimetric characterization of a 3D printed pregnant woman phantom for fetal dosimetry in radiotherapy

A phantom-based estimation of the fetal dose for pregnant women undergoing radiotherapy and its optimization are recommended by the French society for radiation oncology. The objective of this study was to model and print 3D bellies representing various stages of pregnancy, that could be added to a female ATOM® phantom, enabling fetal dose assessment through measurements for optimization studies. The bellies were designed based on fundal height values from gynecological references and printed using a Stratasys 3D Printer and VeroWhite resin. Its chemical composition was determined using a CHONS analyzer: 65.51% carbon (C), 7.95% hydrogen(H), 23.3% oxygen (O), and 2.89% nitrogen (N). Its physical density was assessed using the helium pycnometry method: 1.190 +/-0.001. The linear attenuation coefficients for VeroWhite resin were evaluated using two methods: by calculations based on the linear attenuation coefficients of each chemical element and by experimental attenuation measurements using a 6MV beam. Consistent results were obtained with both methods; the VeroWhite resin is approximately 15% higher attenuation than water according to the calculation method and approximately 12% higher attenuation than RW3 water equivalent plates with the experimental method. These results were considered as acceptable for comparative parametric studies of fetal dose.