Providing better risk stratification power with echocardiographic pressure mapping
First Supervisor: Dr Pablo Lamata
Second Supervisor: Dr Ronak Rajani
Some cardiac conditions cause an obstruction to the blood flow, and thus an extra burden to our heart. Cardiologists then need to measure this extra burden, and use either accurate but risky sensors introduced in vessels or heart, or a non-invasive but less accurate measurement based on echocardiography. The aim of this research project is to equip the cardiologist with the non-invasive and accurate measurement of the extra burden caused by a flow obstruction. This will be possible combining sophisticated imaging and computational technologies. And this will allow the definition of the optimal strategy to resolve the obstruction, with surgery only when actually needed.
The specific objective is to propose an improved assessment of pressure biomarkers for the risk stratification of flow constrictions (i.e. valve stenosis) based on a combination of recent advances in echocardiography (ultrafast acquisition enabling the assessment of blood velocity) and computational flow dynamics (application of Newton’s fundamental laws to make an optimal estimation of the pressure drop with the minimum information).
The project draws a synergy between two areas of research, on the acquisition and on the analysis of medical images. Our research teams are at the forefront on these areas, providing the technology to capture velocity profiles with echocardiography  and resolving the physics of the flow to derive the required pressure drop estimations to resolve the clinical diagnostic and prognostic questions .
Building on this preliminary work, the work of this project is structured as follows:
Task 1: Flow phantom experimental work. The objective is to combine the echocardiographic acquisition  with the pressure mapping analysis . The first hypothesis is the acquisition of the full velocity profile at the cross section of the vessel, at its point of maximum constriction, for an improved estimation of the pressure drop, translating the lessons learned with MRI . The work will entail the construction of the echo compatible phantoms with accurate location of pressure sensors, and the first analysis of the performance of the “out of the box” components of the envisioned solution. Metrics of performance (accuracy in the estimation of pressure biomarkers) of this baseline solution should be available at the end of the first year.
Task 2: Improved acquisition and analysis of flow data. With the understanding of the limitations after the first year, the student will embark in pushing the boundaries of the technology towards the acquisition of blood pressure biomarkers. The challenges of a reduced field of view, of a limiting maximum velocity, and of the definition of the optimal orientation and positioning of the echo probe will be addressed. On the analysis side, the main objective will be the improvement of the data quality through the integration of the redundancy between adjacent heart beats, and trying to capture the information of beat to beat variability. The proposal of a protocol to best characterise the cardiac extra burden should be available at the end of the second year.
Task 3: Clinical translation and evaluation. The goal will be to evaluate the proposed improved analysis in a subset of subjects with aortic stenosis (n=40) that are planned to be studied as part of our BHF Translational Award “Improving the identification of faulty valves”. The pathway will be to engage with GE, our industrial partner in an EU consortium led by P.Lamata, to re-implement our methods into their system. The risk contingency plan will be to search for ethical approval for the use of our ULA-OP experimental platform available in our laboratory.
 C. H. Leow, E. Bazigou, R. J. Eckersley, A. C. H. Yu, P. D. Weinberg, and M.-X. Tang, “Flow Velocity Mapping Using Contrast Enhanced High-Frame-Rate Plane Wave Ultrasound and Image Tracking: Methods and Initial in Vitro and in Vivo Evaluation,” Ultrasound Med. Biol., vol. 41, no. 11, pp. 2913–2925, Nov. 2015.
 F. Donati, S. G. Myerson, M. M. Bissell, N. Smith, S. Neubauer, M. J. Monaghan, D. A. Nordslettern, and P. Lamata, “Beyond Bernoulli: improving the accuracy and precision of non-invasive estimation of peak pressure drops,” Circ Cardiovasc Imaging.