Integrated Ultrasonic Sensors for In-Situ Stent, Graft, or Stent-Graft Patency Monitoring

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This PhD project will develop miniaturised ultrasonic sensing devices for vascular stents and stents/grafts. The goal is to produce a device that can continually monitor the state of the stent or stent/graft, detecting the implant's patency and monitoring for possible stenosis, thrombosis, malposition or leak. Background and motivation - Despite significant improvements in healthcare provision, cardiovascular disease (CVD) remains the number one cause of death in the World. The economic burden to the European Union for cardiovascular disease is estimated at over 196 Billion EUR. This proposal attempts to build towards a smart stent or stent/graft device that can be deployed using existing surgical and catheterisation procedures, yet provides advanced technological abilities that are predicted to reduce patient morbidity and mortality. An implant which can interact and report on its own vessel status, such as when the vessel leaks, re-blocks or clots would be transformative. In this project we will investigate how placing a miniature ultrasonic transducer onto the stent/graft before it is deployed could help to monitor the health of the vessel and the stent/graft within it. Current research on smart stents includes using ultrasound (US) devices for monitoring blood flow velocity or the electrical properties of the device which change in response with the build-up of tissue around the implant. In addition, our proposed US sensor will allow the ultrasonic interrogation of the implant and vessel providing further diagnostic information. This opens up the possibility of endovascular leak detection, monitoring any positive vessel remodelling or the amount and composition of any material building up around the implant, stenosis or thrombosis, giving key clinical data informing on whether further intervention is necessary. Sensing methods - with an ultrasonic transducer integrated onto a cardiovascular implant we will be able to continually measure one or both of two physical properties of the vessel; first the blood flow rate as a Doppler shift flow meter and second the physical anatomy of the vessel, giving the percentage and composition of the occlusion of the vessel using the ultrasonic waves as an imaging method similar to interventional intravascular ultrasound (IVUS) modalities, other possibilities include placing Surface Acoustic Wave (SAW) devices within the implant which could detect material building up in their vicinity. Device placement - a miniaturised sensing device could be placed inside the stent or stent/graft as similar smart devices are proposed to be deployed or with the ultrasound passing through the vessel/device wall easily it could be placed outside the vessel or between the layers of a multi-lumen graft; positioning that has also been proposed for other smart vascular sensors.