Multi echo susceptibility weighted imaging: Improving image contrast by applying the susceptibility weighted phase mask to maps of the R2* decay

Introduction: Magnetic susceptibility weighted phase images (SWI) provide improved anatomical contrast compared to the corresponding magnitude images [1,2]. At 3 Tesla, T2* of white matter (WM) is about 50 ms and T2* of grey matter (GM) is about 65 ms; therefore, a very long TE would have to be used for good GM/WM contrast in a magnitude image. However the GM/WM contrast is present in R2* maps, even if these maps are computed from echoes shorter than the TE for optimum contrast. The purpose of this study was to perform multi echo SWI from which R2* maps and phase maps are computed and then combined into phase filtered R2* maps with improved GM/WM contrast.