Coloured lateral angiograms of the brain of a 65-year-old female patient showing thrombosis (clotting) of the middle cerebral artery, due to a vascular accident, before and after treatment. The left angiogram shows the left internal carotid artery (bottom, white thick line) with clotting of the middle cerebral artery (arrow). The right angiogram taken 45 minutes later after thrombolytic (clot-busting) medication, shows restored blood flow to the affected area of the brain.