Measuring gradient waveforms effectively with fully compensated variable-prephasing

Gradient inaccuracies often deteriorate image quality in non-Cartesian MRI, raising a demand for accurate gradient waveform measurements. The recently proposed approach of “variable-prephasing” provides an efficient gradient measurement technique with high SNR. However, the original variable-prephasing sequence neglects lingering field effects from the prephasing gradients, which we show to produce erroneous results if the gradient system exhibits sharp mechanical resonances. We therefore propose “fully compensated variable-prephasing” and demonstrate its ability to remove all field effects not stemming from the test gradient of interest.