How to reduce trajectory errors caused by non-linear gradient amplifier characteristics

Motivation: The gradient system transfer function (GSTF) can correct k-space distortions arising from gradient imperfections, but is limited by assuming a linear, time-invariant gradient system. Goal(s): We wanted to investigate the linearity of the gradient signal path before and after the gradient power amplifier. Approach: We compared transfer functions for different segments of the gradient chain, measured with positive and negative test pulses. We then predicted the waveform of a trapezoidal gradient with the transfer functions, and quantified the error of the predicted k-space. Results: Using a transfer function based on the gradient amplifier currents halved the errors on the predicted k-space coordinates. Impact: The current-based transfer function could enable a fully automated k-space trajectory determination with doubled accuracy compared to the gradient system transfer function, without special hardware or lengthening scan times. This could help with the clinical translation of non-Cartesian MRI acquisitions.