Optical Interferometric Temperature Sensors for Intravascular Blood Flow Measurements

Lead Research Organisation: University College London
Department Name: Medical Physics and Biomedical Eng

Abstract

Brief description of the context of the research including potential impact;
Coronary heart disease is a leading cause of death and disability in the developed world. It can be caused by atherosclerosis, where lipid-rich plaques can rupture and restrict blood flow. Stenting is an important treatment option but it carries significant risks, including blood clots and re-stenosis. It is therefore of paramount importance to optimize decisions about whether stenting is appropriate. A novel optic fibre intravascular flow sensor is being developed and it could allow for direct and continuous measurements of blood flow. This would especially be of value within cardiology, where intravascular physiological measurements can be of critical importance to determine if stenting should be performed. Current methods include taking pressure measurements as a surrogate for flow, but that correspondence has many limitations, and methods which directly measure blood flow are often difficult to use and produce unreliable measurements. Therefore obtaining direct, reliable, and accurate flow measurements is desirable, and could be achieved by this sensor. If successful in a clinical setting, it has the potential to directly affect the decision making of the clinician into whether or not a vessel requires stenting.
Aims and objectives
The goal of the student is to take the design of the sensor and to test, validate, and optimize it. This involves testing the sensor within bench top experiments, and then exploring various methods to extract the blood flow rates from the signal of the sensor. They will also optimize the system, and help characterize the sensor's performance. In parallel with these experiments, the student is expanding upon an analytical model to describe the system that the sensor is placed in. This will also be tested against a secondary model based on a numeric approach. By understanding the idealized version of the system, this work will inform and optimize the experiments. Later, the sensor will be tested during in vivo experiments which the student will take part in, and they will use the data collected to determine whether or not the sensor is a viable tool, and if the blood flow measurements are accurate and reliable. This could then produce a new version of the method and sensor, and the process would begin again. Ultimately we hope to introduce the optimized sensor in a human clinical pilot study toward the end of the student's PhD.
Novelty of the research methodology
The novelty arises both from the flow sensor itself, and the method in which it is used to measure flow. The sensor comprises a polymer dome at the distal end of a single mode optical fibre, and can measure thermally-induced changes to the dome's length with nanometre resolution. As a temperature sensor, it can measure temperature changes faster, more accurately, and to a higher resolution, than current clinical methods. To measure flow, heat is delivered optically into the fluid, and then temperature is monitored downstream. This is similar to thermodilution, but there the temperature change is induced by manually injecting cold saline. This means that the method used for the sensor would be far preferable, as it does not introduce more liquid into the vessels, and can also be done automatically.
Alignment to EPSRC's strategies and research areas
This research aligns well with the EPSRC's priority areas of "engineering for life and health" and "healthcare device innovation".
Any companies or collaborators involved
There has been very little done to look at the effect of transiently heating a small portion of blood by a few degrees, and so to ensure that the method is safe to use, the student has been collaborating with Imperial College London to explore the effects of heating blood. This will entail looking at clot formation and tissue damage when heating blood.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R512400/1 01/10/2017 30/09/2021
1931389 Studentship EP/R512400/1 25/09/2017 29/09/2021 Elizabeth Carr
 
Description This work is focused upon measuring blood flow using a novel temperature/pressure sensor. The technique involves heating blood upstream of the sensor, and then recording the subsequent temperature changes in the blood downstream. This technique has been used twice in pre-clinical swine models, which is the first time (to our knowledge) in vivo in which time-of-flight flow measurements were performed optically.
Exploitation Route The work is still on going, and is being developed further for commercialisation by EchoPoint Medical Ltd.
Sectors Healthcare

 
Description Worshipful Company of Scientific Instrument Makers Scholarship
Amount £2,000 (GBP)
Organisation Worshipful Company of Scientific Instrument Makers 
Sector Charity/Non Profit
Country United Kingdom
Start 04/2018 
End 03/2020
 
Title Intravasular optical fibre based blood flow sensor 
Description This device is an integrated microcatheter than can be deployed into the coronary arteries in the human heart. It comprises of both pressure and temperature sensors, and will be used to measure blood flow to aid clinical decision making for treatment of ischaemia. It has been tested twice in a pre-clinical swine model, and is being further developed by a spin-out company, EchoPoint Medical ltd. 
Type Diagnostic Tool - Non-Imaging
Current Stage Of Development Initial development
Year Development Stage Completed 2019
Development Status Under active development/distribution
Impact So far this device is still under development, but it is expected that it will improve decision making, especially when deciding on whether or not to stent, which should improve patient outcomes. 
 
Description Science Museum Half Term Activities - 'Build a Body' 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Over two days, the team and I delivered activities at the Science Museum. It was during Half Term, and so it was designed for young children and their families. Over the two days we reached over 1000 people. Children appeared to grow in confidence after trying the activities, and there were many opportunities for thought-provoking conversations with the adults present.
Year(s) Of Engagement Activity 2020
 
Description Science Museum Lates - January 'Medicine' 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact On Wednesday 29th January I delivered interactive activities as part of a stall exploring all-optical ultrasound imaging, materials in healthcare engineering development and the challenges of laparoscopic surgery. This included ultrasound demonstrations, real surgical tools, 'squish-a-phantom' opportunities and an interactive guidewire maze where visitors could experience the difficulties of laparoscopic approaches.
The event took place for 3 1/2 hours, between 6:30 - 10:00, during which time our centre's activities reached over 600 adults visiting this popular cultural event for over 18s interested in the sciences. We reached a range of ages and knowledge levels, pitching explanations based on the reactions, questions and answers of each person.
Year(s) Of Engagement Activity 2020
URL https://www.ucl.ac.uk/interventional-surgical-sciences/news/2020/feb/weiss-features-science-museum-l...
 
Description Science of Surgery - Family activities held at the department 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact This annual event is where various research groups based at WEISS UCL open the dooors and put on activities based on their research to engage with children, their parents, and various other members of the public. The mains aims are to raise local awareness of our work, and to build relationships to facilitate further conversations and collaborations. Last year in 2019 we reached over 300 people, and the centre has had subsequent contact with five local groups to discuss the work. The children also reported being very inspired by the activities that I took part in.
Year(s) Of Engagement Activity 2019,2020
URL https://www.ucl.ac.uk/interventional-surgical-sciences/science-surgery