 BACKGROUND: Thrombolytic drugs may dissolve blood vessel clots in acute ischemic stroke. The overall benefit of intravenous thrombolysis is substantial, but up to 23 of patients with large clots may not achieve re-opening of the vessel and up to 40 of the patients may remain severely disabled or die. Ultrasound accelerates clot break-up lysis when combined with thrombolysis sonothrombolysis and increases the likelihood of functional independence at 3 months. Adding intravenous ultrasound contrast gaseous microspheres further enhances the thrombolytic effect contrast enhanced sonothrombolysis CEST. Contrast enhanced ultrasound may also accelerate clot break-up in the absence of thrombolytic drugs contrast enhanced sonolysis CES. 