Venous vessel boundary delineation at high field using sigmoid-SWI

Susceptibility Weighted Imaging (SWI) is an increasingly utilised MRI technique for enhancing image contrast by attenuating magnitude data with a mask derived from the phase data. It is particularly useful for venography, however at higher field strengths, the effects of localised magnetic susceptibility differences lead to ill-defined edges within SWI images and overestimation of widths in large veins oriented perpendicular to the main field. We propose a variation on SWI, sigmoid-SWI, that removes the vessel boundary artefacts, resulting in clearer visibility of edges and more accurate widths of venous vessels.