Project Summary/Abstract Timely diagnosis of stroke (ischemic vs. hemorrhagic) is critical to streamlining appropriate treatment and achieving optimal clinical outcomes–minimizing damage to brain tissue and function. About 87% of strokes are ischemic, with large vessel occlusions (LVOs) accounting for >90% of deaths among this subset. Patients with LVOs are best treated with mechanical thrombectomy at a certified comprehensive stroke center (CSC) hospital as soon as possible, but the nearest non-CSC stroke-care facility may lack this interventional catheterization capability. Transcranial Doppler (TCD) ultrasound can measure vascular flow and detect LVOs, but current TCD equipment has high operator dependence: to acquire a TCD signal, the user must simultaneously find the optimal “acoustic window” of a patient’s skull and precisely align the ultrasound beam with the middle, anterior, or posterior cerebral arteries. We propose to design a transcranial ultrasound device that enables paramedics to identify LVOs quickly and easily as part of stroke triage, to reduce the time to tPA and thrombectomy treatment delivery (by tens of minutes to >1 hour) and improve ischemic stroke outcomes. This new TCD device will include a customized 2D transducer array that can (1) sample and map trends in acoustic properties over an area of the skull and (2) detect angled wavefronts from moving blood scatterers within the beam. To achieve this design, our team–consisting primarily of undergraduates–will take thorough experimental acoustic measurements of ex vivo skull, acquire transskull Doppler measurements on a custom phantom using a commercial array probe, and perform transskull simulations of unique transducer array geometries. These efforts will pinpoint ideal acoustic windows and yield a high-resolution, digital acoustic model of temporal skull, provide signals from which to refine an algorithm to guide the placement and angle of a TCD transducer, and ultimately optimize the layout and operation of a custom 2D array streamlined for TCD acquisition (and LVO detection) by untrained users. This project will lead to further research (prototype fabrication and in vivo testing) and applications in detecting and monitoring various neurological and cardiovascular conditions. Long-term, we envision cost-effective, user- friendly TCD used in ambulatory care units across the country, and improved transcranial imaging and therapy capabilities as well. The project will provide a closely mentored biomedical research experience to a diverse set of undergraduates, whose success as researchers and role models will significantly impact and enhance the research environment at the University of Memphis and collaborating institutions across the Mid-South.

Project Narrative There is a critical need for a practical means of quickly detecting severe ischemic stroke when paramedics make first contact with a patient. This primarily-undergraduate research project proposes to optimize the design of a transcranial Doppler device and a user-guidance algorithm for this purpose, aided by thorough analysis of ultrasound signals to characterize temporal skull bone. This device design will lead to improved stroke outcomes, including lower rates of mortality and long-term disability, with lower costs for patients and the health care system.