Alison Burgess PhD, Presenter: Nothing to Disclose

Yuexi Huang PhD, Abstract Co-Author: Nothing to Disclose

Milan Ganguly, Abstract Co-Author: Nothing to Disclose

David Goertz PhD, Abstract Co-Author: Nothing to Disclose

Kullervo H. Hynynen PhD, Abstract Co-Author: Nothing to Disclose

Thrombolysis is the most effective method to treat ischemic stroke. Currently the only clinically approved thrombolytic therapy is the administration of tissue plasminogen activator (tPA) which has serious potential side effects. The purpose of this study is to demonstrate that high intensity focused ultrasound (HIFU) is an effective thrombolytic therapy which may be an alternative to tPA for some patients.

Rabbits were anestethized and a craniotomy was performed 2 weeks prior to treatment to ensure proper ultrasound wave propagation. On treatment day, arterial blood clots were formed with super-paramagnetic iron oxide and injected into the internal carotid artery. Fluoroscopy was used to confirm blockages in blood flow. Animal were then placed on the HIFU positioning system inside a 3.0T MRI. Fast gradient echo sequences (TE: 15ms) were used to locate the iron-loaded blood clot and to precisely target the HIFU beam. A 1.5MHz single element transducer was used to sonicate the blood clot (300W, 1 ms bursts, 20 s duration, 0.1% duty cycle) through the cranial window and intact skin. Following treatment, animals were re-imaged with MRI to detect changes in tissue integrity and with fluoroscopy to confirm that reperfusion had been established.

In animals where the embolus lodged beneath the cranial window, HIFU treatment was applied (n=3) and reperfusion was observed 100% of the time.  Those animals in which the embolus remained outside of the cranial window and were hence untreatable with HIFU were used as controls (n=4).  Reperfusion did not occur in any untreated animal. Histological analysis indicated minimal damage to the brain tissue following HIFU treatment.  

Our data suggests that HIFU induces thrombolysis in an embolic model of stroke. Development of a phased array transducer capable of transmitting through the skull will make these results directly transferable to the clinical setting.

HIFU may provide a safe and effective alternative to tPA for treatment of acute ischemic stroke.

Burgess, A, Huang, Y, Ganguly, M, Goertz, D, Hynynen, K, High Intensity Focused Ultrasound (HIFU) Treatment of Acute Stroke.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034499.html