Susceptibility-weighted imaging in intracranial hemorrhage: not all bleeds are black.

To correctly recognize intracranial hemorrhage (ICH) and differentiate it from other lesions, knowledge of the imaging characteristics of an ICH on susceptibility weighted imaging (SWI) is essential. It is a common misconception that blood is always black on SWI, and it is important to realize that hemorrhage has a variable appearance in different stages on SWI. Furthermore, the presence of a low signal on SWI does not equal the presence of blood products. In this review, the appearance of ICH on SWI during all its stages and common other causes of a low signal on SWI are further discussed and illustrated.