The effect of concomitant gradient fields on MRI with long readout radial‐based trajectories

Concomitant gradient fields are found to produce non-negligible imaging artifacts in long readout radial-based trajectories due to variations in the associated phase accrual across view angles. Azimuthal rotation of the readout direction down the echo train, as implemented in the helical EPI and helical stack-of-stars trajectories, is shown in simulations, phantoms, and in vivo to mitigate these effects. Substantial improvement is seen in cases of nonaxial imaging with multiple contrasts, quickly varying B₀ inhomogeneity, and/or high gradient amplitudes.