Parallel Transmission with Spectral-Spatial Pulses for Susceptibility Artifact Correction

Cungeng Yang¹, Weiran Deng¹, Vijayanand Alagappan², Lawrence L. Wald³, Victor Andrew Stenger¹

Susceptibility induced signal loss is a major limitation in high field T2*-weighted MRI applications including BOLD fMRI. Spectral-spatial (SPSP) pulses have been shown to be very effective at reducing through-plane signal loss in axial slices using a single excitation. SPSP pulse design assumes a linear relationship between off-resonance frequency and through-plane susceptibility gradient Gs(f)=αf. This approximation holds well in more superior slice locations, however, inferior slices can have several regions that require different αs. We propose the use of parallel excitation to apply unique SPSP pulses with each transmitter. The localization introduced by the transmission sensitivities compensates for the spatial distribution of the susceptibility gradients. The method is demonstrated in T2*-weighted human brain imaging at 3T with an eight-channel parallel transmission system.