Hemorrhage on MRI Dr Derek Smith ◉ and Assoc Prof Frank Gaillard ◉ ◈ et al. Hemorrhage on MRI has highly variable imaging characteristics that depend on both the age of the blood, the type of hemoglobin present (oxy- deoxy- or met-), on whether or not the red blood cell walls are intact and the specifics of the MRI sequence. Although MRI is often thought of as not being sensitive to acute hemorrhage, this is not, in fact, true particularly with more modern sequences 5,7 . The appearance of hemorrhage will, however, be different at different times and is not perfectly stereotyped, as such caution should be exercised in precisely aging hemorrhages. Physiology The factors that affect the appearance of hemorrhage on MRI vary according to the sequence. The oxygenation state of hemoglobin and the location of either contained within red blood cells or diffused in the extracellular space have a tremendous effect on the imaging effects of blood. The three hemoglobin states to be con
