Improving Treatment of Stroke: Guiding Endovascular Mechanical Thrombectomy

Abstract: In the last few years there has been a revolution in the treatment of ischemic stroke. Thrombus dissolving drugs help many patients but have limited effectiveness when the large cerebral arteries are blocked. It has recently been shown that physically removing the thrombus through a catheter is remarkably effective at reducing the damage to the brain. Removing the thrombus can be effective up to 24 hours after the onset of symptoms. The retrieval method that is most consistently effective is to engage the thrombus with a stent-like retriever and use the retriever to pull the thrombus back into a catheter. One of the challenging aspects of removing the thrombus with this method is that the thrombus cannot be directly visualized during the process of retrieval. The thrombus can be left behind as the stent is pulled back, or fragments of the thrombus can break off and lodge downstream where they cannot be reached. The thrombus itself cannot be seen in x-ray images so there is no way to know how completely the thrombus is being moved with the stent-retriever.We propose to develop unique magnetic nanotechnology to monitor mechanical extraction of these thromboses. The thrombus will be coated with magnetic nanoparticles and the signal from those nanoparticles will be used to monitor the position of the thrombus relative to the stent-retriever. Using the stent-retriever itself as an antenna, one can measure signal from nearby magnetic nanoparticles bound within the thrombus. We will demonstrate that the signal changes dramatically if the thrombus moves relative to the stent-retriever or if a fragment breaks off the thrombus. We will also demonstrate that it is possible to produce images of the thrombus during thrombus removal. These tools will enable the physician to reduce procedure time, more consistently remove the entire thrombus which we expect will improve patient outcomes.