Zero-gradient-excitation ramped hybrid encoding (zGRF-RHE) sodium MRI

Abstract

Purpose: Fast bi-exponential transverse signal decay compounds sodium image quality. This work aims at enhancing image characteristics using a special case of ramped hybrid encoding (RHE). Zero-gradient-excitation (zGRF)-RHE provides (1) gradient-free excitation for high flip angle, artifact-free excitation profiles and (2) gradient ramping during dead-time for the optimization of encoding time (tenc) to reduce T2* signal decay influence during acquisition. Methods: Radial zGRF-RHE and standard radial UTE were investigated over a range of receiver bandwidths in simulations, phantom and in vivo brain experiments. Central k-space in zGRF-RHE was acquired through single point measurements at th..