All-inclusive Safety Models Limit Imaging Performance at 7T

Safety models on scanners are patient-position unaware and may include multiple patient positions to ensure safety. This may lead to overestimation of the specific absorption rate (SAR) and limit scanning performance. This study investigates the effect of an all-inclusive safety model on SAR estimation for parallel-transmit and quadrature-excitation at 7T. Results show that more than 4-fold SAR overestimation can be commonly observed. RF shimming suffered the most, with 11-fold overestimation at the worst-case and more than 4-fold overestimation in 37% of cases. RF shimming also offered the lowest peak local SAR and may be unnecessarily penalized by overconservative safety models.