Hemorrhagic and non-hemorrhagic causes of signal loss on susceptibility-weighted imaging.

Susceptibility-weighted imaging (SWI) plays a key role in an emergency setting. SWI takes the intrinsic properties of materials being scanned and creates a visual representation of their effects on the magnetic field, thereby differentiating a number of pathologies. Magnetic resonance imaging (MRI) is now more often used, especially when computed tomography (CT) is inconclusive or even negative. Often, clinicians prefer to obtain an MRI first. This article will review the various hemorrhagic and non-hemorrhagic causes of low signal on SWI. There will be a focus on the distribution patterns of low signal on SWI in pathologies such as diffuse axonal injury, cerebral amyloid angiopathy, and cerebral fat embolism. It is important to recognize these patterns of susceptibility, as the radiologist may be the first to give an accurate diagnosis and therefore, directly impact clinical management.