Abstract: A method is presented for correcting Maxwell term error artifacts produced by an NMR system during the production of either a phase contrast angiogram or a complex difference angiogram. Phase corrections are made to the reconstructed phase image to eliminate the artifacts. Correction coefficients calculated from the flow encoding magnetic gradient waveforms of the phase contrast pulse sequence are used in a polynomial to calculate a set of phase error corrections. These corrections are then used to adjust the phase at each pixel of the angiogram image.

Abstract: An MRI method and system in which phase gradients and read gradients overlap over varying time durations. The MRI signals sampled while there is no overlap fill a non-rectangular matrix in K-space. Alternately, the MRI signal is sampled during the times of overlap as well but a zero is placed at the corners of the matrix at locations which correspond to overlap. The benefit include a reduction in the MRI data acquisition time for the same spatial resolution as known sequences, an increase in image spatial resolution for the same MRI data acquisition time as known sequences, lower signal bandwidth and increase the image signal-to-noise ratio (SNR). In addition, in a gradient echo MRI sequence, the read and write gradients do not overlap in time but vary in width (or at least one of the them varies in width) with time to achieve similar advantages.

Abstract: A method is disclosed to remove the image artifacts produced by Maxwell terms arising from the imaging gradients in an echo planar imaging pulse sequence. The frequency and phase errors caused by the Maxwell terms are calculated on an individual slice basis. During the subsequent data acquisition these errors are compensated by dynamically adjusting the receiver frequency and phase.