Leveraging high-performance head-only gradients to enable ~2-fold higher multiband acceleration in SMS-EPI and SMS-EPTI

Abstract

High-performance head-only gradient systems can substantially reduce echo spacing (ESP) in echo-planar imaging (EPI), but the resulting encoding speed is typically used to shorten readouts and reduce distortion. Here, we instead leverage the increased echo budget to enable denser k-space sampling and higher simultaneous-multislice (SMS) acceleration in SMS-EPI and SMS-EPTI. Fast k-space traversal with denser ky-kz sampling is achieved using peripheral nerve stimulation (PNS)-optimized gradient waveforms, while high-quality reconstruction is obtained using field-correcting GRAPPA (FCG). The resulting ESPs on MAGNUS 3T and Impulse 7T are approximately half those of high-performance whole-body systems, enabling approximately 2-fold higher multiband (MB) acceleration. This facilitates high-quality 2.5-mm isotropic whole-brain resting-state fMRI at 7T with MB28 and a repetition time (TR) of 123 ms.