Abstract
Many strokes are caused by emboli from distal sites blocking vessels in the brain. The discovery that emboli of various types can be detected using Doppler ultrasound as they are carried through the major cerebral arteries has led to a new field of study, which has considerable potential. The basic principle of detection is extremely simple: if an embolus backscatters more power than the surrounding blood in which it is moving, then the transient increase in power can be detected and measured. Questions that arise from this principle surround the circumstances under which such power increases can be detected, and whether the size and composition of the embolus can be inferred from such measurements.
In this seminar I will present the clinical background to embolus detection, the basic theory of embolism detection and classification, and describe how embolus monitoring has dramatically affected the outcome for patients undergoing carotid artery surgery. Finally I will describe a series of technical developments related to the detection of emboli and experiments designed to elucidate the effects of embolism on blood flow to the brain.
Short biography
David Evans is Professor of Medical Physics in the Department of Cardiovascular Sciences at the University of Leicester and an honorary Consultant at the University Hospitals of Leicester NHS Trust. He gained his Ph.D. from the University of Leicester and his D.Sc. from the University of Surrey. His principal research interests are related to Doppler ultrasound physics and signal processing, and applications of Doppler ultrasound in the cerebral circulation. He is the principle co-author of two textbooks on Doppler ultrasound physics, has authored over 200 peer reviewed papers, and lectured in 24 different countries around the world. He has served as President of the British Medical Ultrasound Society, President of European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB), and is currently the Honorary Secretary of the World Federation for Ultrasound in Medicine and Biology.