A 3-dimensional magnetic resonance image form a patient who has undergone an acute myocardial infarction. The heart is visible in the center of the image. Healthy (non-infarcted) cardiac muscle is indicated by asterisks, whereas arrows point to the infarcted region. MRI can reveal the extent of the area affected by inflammation after a heart attack (the yellow infarcted region marked by arrows). Serial MRI studies reveal that this inflammatory reaction appears immediately after the infarction but then rapidly resolves and then reappears several days after the infarction.