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