Figure 1.

Evolution of intraparenchymal hemorrhage on magnetic resonance imaging. (A) In the earliest stage of acute hematomas, blood is still oxygenated within intact red blood cells (RBCs). (B) Rapid deoxygenation occurs, first at the periphery and then throughout the hematoma, but the RBCs remain intact. (C) As the lesion undergoes oxidation, the peripheral hemoglobin within intact RBCs forms methemoglobin. (D) This oxidation process and conversion to methemoglobin occur throughout the hematoma and subsequently the RBCs lyse. (E) As free methemoglobin is formed, hemosiderin and other iron storage forms are deposited within macrophages in the adjacent brain parenchyma. Eventually, the lesion contains no intact RBCs, and methemoglobin is resorbed or metabolized, leaving only a collapsed cleft lined by hemosiderin and ferritin without any notable central constituents.