MO-E-AUD B-07: SAF Values for Internal Electron Emitters Calculated for the RPI-P Pregnant-Female Models Using Monte Carlo Methods

Abstract

Purpose: to calculate specific absorbed fraction (SAF) values for internal electron emitters based on more realistic RPI‐P serial pregnant female models. Method and Materials: The RPI‐P series pregnant‐female models developed by Xu and coworkers were used for Monte Carlo simulation. Those models are based on boundary‐representation method for organ delineation. The image sources are from clinical CTimage, VIP‐Man image, and public domain images. The pregnant woman models, RPI‐P3, RPI‐P6, and RPI‐P9, were implemented into a previously developed Monte Carlo user code, EGS4‐VLSI. In this study, internal electron emitters were considered for the following energies: 10, 15, 20, 30, 50, 100, 200, 500, 1000, 1500, 2000, and 4000 keV. SAF values to the fetus were calculated for each of these energies involving 35 source organs.Results and Discussion: SAF factors from source organs to the fetus have been calculated for all the three pregnant female models. Results show that electron SAF values follow linear relationship as equation: log (SAF(fetus ← source) = A ⋅ log (E) + B , where E is the electron energy, A and B are coefficients. A and B coefficients were calculated. R2 coefficient, the determination for the linear relationship, is ranging from 0.90∼1.00 except source organ=heart for RPI‐P3 model. It means the linear relationship between log(SAF) and log(E) is fitting well. Conclusion: SAF values have been derived based on a new developed RPI‐P series pregnant‐female models using Monte Carlo method. For electron emitters ranging from 10 keV to 4000 keV, the log(SAF) and log(energy) relationship can be approximated by linear function.