Reduction of Required Gradient Spoiler Size for AFI B1 Mapping

Kim Shultz¹, Greig Scott¹, John Pauly¹

AFI is a powerful, fast technique for B1 mapping, useful for quantitative imaging and parallel transmit pulse design. It is made more difficult by the requirement of very large gradients to spoil the transverse magnetization at the end of each TR. We present a technique to correct for the error that occurs with small spoiler gradients based on the expected reconstruction error seen in simulations for various tissues. This allows accurate AFI results with more reasonable gradient sizes. Additionally, the error seen in lipids is smaller than that seen with very large spoiler gradients.