B1 Insensitive Genetically Altered Refocusing Pulses for Ultrahigh Field Spin Echo Imaging

Aaron Christopher Hurley^1,2, Andrew Peters¹, Uwe Aickelin², Li Bai², Penny Anne Gowland¹

Urgurbil et al. proposed the use of a Numerically Optimised Modulation (NOM) scheme to improve the adiabaticity over the whole length of a BIR4 pulse and this method provides better performance for shorter pulses. NOM resamples the AM and FM functions with reference to the adiabatic condition and is restricted to looking at on-resonance effects. Following from this work, we attempted to optimize the resampling function via a Genetic Algorithm. The evaluation function considers B1 and B0 inhomogeneities to tailor the optimization to 7T conditions, requiring the study of off-resonance behaviour.