Susceptibility Weighted Imaging

Abstract

Susceptibility-weighted MRI (SWI) offers unique and complementary information to the conventional contrasts typically used in magnetic resonance imaging (MRI). It uses both magnitude and phase information of high-resolution gradient-echo-based sequences, which is then further post-processed to improve vascular conspicuity and/or tissue contrasts due to the presence of susceptibility sources. SWI has become an established widely used clinical tool, particularly for neuroimaging and imaging vascular pathologies. It is a qualitative technique that is limited by the orientation-dependent and nonlocal nature of the phase and is unable to distinguish unambiguously between positive and negative magnetic susceptibilities. The more recent development of quantitative susceptibility mapping (QSM) overcomes these limitations and allows the generation of three-dimensional maps showing the variation of the relative magnetic susceptibility within the human brain. This chapter provides a background of the SWI method and reviews current research and clinical applications. It also highlights some of the limitations and outlines potential future directions of the technique.