SAR Reduction using Non-Linear Gradients

Emre Kopanoglu^1,2, Burak Akin¹, Vakur B. Erturk², Ergin Atalar^1,2

Slice-profile is related to the frequency-spectrum of an RF envelope through the gradient field, which is conventionally linear. Although a rectangular pulse is more efficient as far as SAR is concerned, apodized sinc envelopes are widely used for excitation because the slice-profile of a rectangular pulse is not desirable. In this study, a method that employs non-linear gradients to modify the slice-profile of a rectangular pulse into a feasible one is proposed. As a sample study, the method is compared to an apodized sinc envelope, and showed 41% reduction in SAR as well as an increase in correct excitation in the region of interest from 71% to 94%.