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Image Acquisition and Reconstruction (pre-2019)

Photoacoustics and ultrasound computed tomography

Project ID: 2018_113

Student: Joseph Hansen-Shearer

1st Supervisor: Mengxing Tang, Imperial College London
2nd Supervisor: Rob Eckersley, King’s College London
3rd Supervisor: Mike Warner, Imperial College London
4th Supervisor: Jeffrey Bamber, Institute of Cancer Research

Project Aims:

This project aims to develop and evaluate novel computed tomographic techniques using light, sound, and advanced image reconstruction algorithms which are based on wave physics and has seen great success in geophysics to detect oil and gas deposits (see figure1), in order to achieve high resolution images of rich structural and functional information in a living body. Multiple tissue properties, including their colour (optical absorption spectrum), acoustic reflectivity and absorption, speed of sound (how fast sound travels within them), all of which are closely related to the physiological and pathological status of tissues, will be mapped in high spatial resolution and contrast. This project, if successful, would have implications in a wide range of applications including cancer and cardiovascular diseases.

Figure 1. The description is in the caption.

Figure 1: The significant improvement of image reconstruction of earth structure achieved through advanced reconstruction algorithm based on improved physics. The colour represents speed of sound.

Project Background:

Photoacoustic Tomography (PAT) is an emerging imaging modality which is able to measure tissue optical properties (e.g. colours) far beyond the penetration depth limit by traditional optical-only imaging techniques such as optical microscopy (<1mm). By shining short (and safe) laser pulses into the tissue, ultrasound waves can be generated when tissue absorbs the laser energy and transiently expands. Such ultrasound signals can be detected at the body surface and used for reconstructing an optical absorption map. By measuring at multiple optical wavelengths, the technique can generate tissue functional information, including blood oxygenation and imaging of dye-labelled molecular contrast agents, non-invasively.

On the other hand, ultrasound has been one of the most used clinical front-line imaging modalities. Existing ultrasound pulse-echo imaging is able to visualise tissue structure, tissue mechanical properties and blood flow dynamics. The combination of PAT with ultrasound offers a 3D tomography system with rich structure as well as functional information, with very little extra hardware complexity and cost. While PAT and ultrasound tomography have shown great promise, the current image reconstruction methods still make some important simplifications of the physics, compromising image quality.

Proposed Work:

In this project we would like to develop novel PAT and ultrasound computed tomographic techniques to achieve high resolution images of rich structural and functional information in the living body. These will include advanced image reconstruction algorithms based on models of wave physics which have seen great success in geophysics to detect oil and gas deposits.

The project contains both computational and experimental elements. We will establish the feasibility of the tomographic techniques in computer simulation first, followed by experimental studies on both phantoms and in pre-clinical models in vivo, to reconstruct high resolution multiple tissue optical and acoustic parameters of clinical relevance. The work will take advantage of the state-of-the-art PAT and ultrasound research hardware system available to this project containing both a pulsed laser, a ring ultrasound transducer array, 256 programmable parallel pulsing and data acquisition channels, as well as the state-of-art image reconstruction algorithms in earth science and engineering research.

The project will be jointly supervised by a multidisciplinary team from Imperial College London (Bioengineering, Earth Science and Engineering), King’s College London (Biomedical Engineering), and Institute of Cancer Research, Sutton, London. A willingness to engage in the multidisciplinary nature of the work (physics, engineering, computing, experimentation and biology) and to travel between sites as the work requires, is important.

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