Tissue detail of pregnant body models needed to estimate SAR for fetal MRI

Motivation: Due to the large variation of the body shape and size in the pregnant population, several pregnant body models are needed in fetal MRI safety studies. However, creating detailed pregnant body models is challenging. Goal(s): Our goal is to investigate the effect of reducing maternal tissue detail on maternal and fetal SAR. Approach: We simplified >18 maternal tissues into 3 (muscle, lung and fat) in 7 pregnant body models and quantified the change in maternal and fetal SAR. Results: The value and location of maternal and fetal SAR changes by up to 13% and 34 mm with maternal tissue detail reduction. Impact: Simplification of maternal tissues into muscle, lung and fat changes maternal and fetal SAR (<14%) significantly less than the variation of SAR between pregnant subjects (>x2) and might provide a good trade-off between accuracy and practicality in RF safety studies.