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Image Acquisition and Reconstruction (pre-2019)

High resolution and high contrast imaging and quantification of cardiac macro- and micro- blood flow based on ultrafast ultrasound acquisition and signal processing

Project ID: 2017_101

Student: Carlos Cueto Mondejar

1st supervisor: Mengxing Tang, Imperial College London
2nd supervisor: Rob Eckersley, King’s College London

The aim of this project is to develop and evaluate the next generation echocardiography techniques for accurate and early diagnosis of e.g. coronary artery diseases and thrombus, taking advantage of ultrafast ultrasound acquisition (kHz frame rate), microbubble contrast agents and signal processing.

Ultrasound imaging is one of the most frequently used clinical imaging modalities and is the first line imaging technique for a wide range of diseases especially cardiac applications. Comparing with other existing established clinical imaging modalities ultrasound imaging is a real-time imaging tool that is far more affordable and accessible at point of care.

Two notable recent advances in medical ultrasound include the development of ultrafast ultrasound imaging systems and ultrasound contrast agents. The techniques offers super high frame rates (thousands of frames per second) and high sensitivity of vascular imaging and have potential to revolutionise the field of both clinical and pre-clinical ultrasound. The potential application of the ultrafast ultrasound in cardiac imaging offers exciting new opportunities in tracking fast wall motion and rapid flow field within the chambers, and quantification of the microvessels within myocardium.  Quantification of micro-vascular flow in myocardium is the holy grail in the early diagnosis of coronary heart diseases. Flow in the chamber is also closely related to cardiac function and has potential value to predict thrombus formation – a serious clinical condition. Conventional ultrasound (tens of frames per second) is not fast enough to reliably track the fast wall motion and flow both within the wall and in the chamber.

This project will explore opportunities opened up by applying ultrafast ultrasound and microbubble contrast agents to cardiac imaging and address the challenges in the large methodology gap between ultrafast platforms available and the cardiac applications. We will focus on three aspects: signal processing/image formation, transmit pulsing scheme, and particle image tracking. More specifically, firstly we will develop ultrasound pulsing schemes that generate higher and more homogeneous imaging sensitivity. Currently short duration diverging waves are used which attenuate in depth and consequently imaging sensitivity is spatial dependent. We will explore and optimise transmission that is between focusing and diverging scheme and use pulse encoding to increase sensitivity. Secondly we would like to firstly develop techniques to process the large amount of data acquired in short period of time afforded by the ultrafast ultrasound to improve final image resolution and contrast, through exploring linear and nonlinear processing of the temporal data on multiple transducer sensors generated from different ultrasound insonation angles. The aim is to accurately quantify micro-vascular flow in the myocardium. Our initial study to use simple correlation between signals from different sensors has already generated very promising results on other organs and this PhD project will build on this work to develop more advanced signal processing for the heart. Finally we will generate heomodynamics information within the heart chambers by tracking contrast agent particle movement, and to estimate both 2D flow velocity field and flow in the 3rd dimension using speckle decorrelation in that dimension, in order to detect flow stagnation, which is a high risk factor for thrombus formation.

We have complementary advanced programmable ultrasound research systems  at ICL and KCL which provide the hardware platform for this project. This project has a mixture of both experimental and signal processing work.

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