The Inner Lives of Voxels: Revisiting the Basics for Nonlinear Gradient Imaging

Gigi Galiana¹, Jason Stockmann², Leo K. Tam², Robert Todd Constable^1,2

This work examines the prototypical MR echo that would expected for a voxel of spins evolving in a strong quadratic (2z2-x2-y2) gradient field. This case is increasingly relevant given the growing interest in nonlinear imaging, and we report several surprising differences from the linear case, both in magnitude and phase of the echo. Furthermore, we show that neglecting these dynamics can lead to significant errors even in basic sequences, such as those routinely used for field mapping.