Partial field-of-view spiral phase-contrast imaging using complex difference processing.

Rapid flow imaging was achieved with a partial field of view (pFOV) spiral motion-encoded technique. The FOV and the acquisition time were reduced by a factor of 2 by undersampling k-space. The pFOV spiral k-space trajectory aliased signals from outside a circular ring whose radius was inversely proportional to the distance between adjacent spirals in k-space. In this study the FOV was adjusted so that all of the moving spins were located inside the inner half circle of the full FOV. Complex subtraction of two differentially flow-encoded images was used to remove the spurious phase sources and provide an accurate measurement of flow. The complex subtraction process also serves to eliminate aliasing artifacts that are generated by static tissue from outside the reduced FOV. Experiments in a flow phantom and volunteers showed that the flow estimates obtained by pFOV spiral motion encoding are in good agreement with the estimates reconstructed using complex difference processing. Copyright (c) 2006 Wiley-Liss, Inc.