Department of Cardiovascular Sciences

Transcranial Ultrasound

A major cause of stroke comes from embolic debris (thrombus, bubbles and pieces of plaque) that travel through the cerebral circulation and become lodged in arteries supplying the brain. Our research group has extensive expertise in the detection and characterisation of cerebral emboli using transcranial Doppler ultrasound. Recent advances include the development of software to estimate the sizes of air bubbles entering the cerebral circulation during cardiac surgery, use of 'virtual patient' simulations to estimate the impact of bubbles on cerebral blood flow, and development of digital MR subtraction software to assist Radiologists in identifying new embolic lesions. We are also investigating the potential for using an acoustic radiation force to deflect emboli away from the brain and to distinguish solid emboli from bubbles.

Detection and deflection of emboli in the bloodstream

This Engineering and Physical Sciences Research Council (EPSRC) study (P.I. Dr Emma Chung) is investigating the feasibility of using an ultrasound acoustic radiation force to deflect emboli away from vital organs, such as the brain, during surgery. We are also investigating whether differing responses of solid and gas emboli to an acoustic radiation force could provide a reliable method for distinguishing between harmful solid emboli and benign gas bubbles.

Brain injury during heart surgery

This British Heart Foundation (BHF) study (P.I. Dr Emma Chung) was the first to determine the size distribution of bubbles and volume of air entering the cerebral circulation during heart surgery. We compared the incidence, timing, and properties of bubbles released into the bloodstream during surgery with brain injury assessed using MRI and cognitive testing and found no links between the number or sizes of bubbles and brain injury. The PhD student who performed this study, Dr Nikil Patel, was awarded a College PhD prize and the results of this study were published on the cover of Stroke.

Modelling embolic stroke

This collaboration with Open University theoretical physicist, Dr Jim Hague, led to development of the first computational model of embolic stroke. Our 'virtual patient' simulations are capable of taking information about the size and composition of emboli experienced intraoperatively to provide real-time estimates of the likely impact of emboli on cerebral blood flow.

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