Medical Physics and Biomedical Engineering


UCL Medical Physics researchers awarded funding in EPSRC New Horizons initiative

3 October 2022

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Two projects led by UCL Medical Physics and Biomedical Engineering research teams have received EPSRC funding through the New Horizons initiative.

Each awarded project focuses on high risk, speculative engineering or information and communication technologies research with a potentially transformative impact.

The projects are supported by a £15 million investment from the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation, through the New Horizons initiative.

EPSRC Executive Chair Professor Dame Lynn Gladden commented:

“The adventurous thinking displayed in these new projects underlines the ingenuity and imagination of our research base, taking novel approaches to tackle major challenges. The discovery-led science we support is at the heart of the research and innovation ecosystem. Engineering and physical sciences underpins and advances research across all disciplines, catalysing the breakthroughs and technologies that deliver benefits and prosperity for all of society.”

Our Projects

Complete Material Characterisation Through A Single Polychromatic X-ray Scan

Research team: Professor Peter Munro and Professor Sandro Olivo

Project outline: X-ray computed tomography (CT) is a powerful technique for imaging three-dimensional objects revealing the interior of a sample. X-ray CT is routinely used in medical imaging and industrial inspection, for example. Currently, contrast in X-ray CT images is largely based upon how strongly X-rays are attenuated by the sample. For example, bones in the human body strongly attenuate X-rays incident upon them, which is why bones, which are highly attenuating, appear with relatively high contrast in X-ray CT images. There is much interest in extending X-ray CT to be able to identify particular materials in a sample. For example, personalised diagnosis of complex diseases increasingly involves the use of imaging agents. Our method would provide the ability to pinpoint multiple agents simultaneously in a single scan, allowing for more effective diagnostic tests to be performed in a simple and speedy manner

At present, material identification using X-ray CT can only be performed using two separate CT scans which therefore takes twice the amount of time of a single CT, thus delivering double the radiation does to the sample. Furthermore, this approach only works for monochromatic X-ray source, such as are available at synchrotrons, which are expensive to operate and have very limited capacity. Even if synchrotron access is possible, in many applications, such as medical imaging, performing two scans is not feasible due to the dose they can safely receive. More recently, methods which make use of expensive detectors can achieve this using a single scan, however severely limiting the sample size.

We propose a method of performing material identification which uses a single phase-sensitive CT scan and is based on the edge illumination x-ray phase imaging technique which employs standard, therefore cost effective, x-ray imaging equipment. Our technique works by recognizing that three-dimensional images of electron density and effective atomic number, reconstructed from a single edge-illumination CT data set will only have sharp interfaces between two materials when both of these materials have been correctly identified. Thus, the unknown material can be determined by varying a reconstruction parameter and inspecting an interface between the known and unknown materials. The parameter which leads to this interface becoming sharp essentially reveals the unknown material. This phenomenon can be used sequentially to identify all materials in a sample, resulting in complete material identification using a single CT scan.

The Novel High-accuracy Impedance Tomography Enabled by the Time-of-flight EIT via CHIRP Current Excitation (CHIRP-EIT)

Research team: Dr Kirill Aristovich, Prof David Holder and Dr Enrico Ravagli

Project outline: There is currently no technique that can non-invasively image the functional activity in the brain with sufficient spatial and temporal resolution. In addition, there is a need to have a rapid, precise and portable imaging technique for a variety of medical applications spanning from stroke, where rapid imaging on the back of an ambulance can be lifesaving, to conditions like acute respiratory distress syndrome (ARDS) along with a multitude of other acute conditions, treatment of which could be greatly improved with having bedside continuous imaging system.

The traditional Electrical Impedance Tomography (EIT) produces images of the internal electrical impedance of a subject using arrays of electrodes (usually 32) placed around the object of interest (e.g., human head). Imperceptible, very low amplitude known current is injected between a pair of electrodes at a time, while electric potentials are measured on the remaining electrodes. By rapid switching of current injections between the possible pairs of electrodes, multiple measurements are made which then can be reconstructed into the image of internal conductivity, the variations of which from the normal values are indicative of various pathologies (e.g., stroke). EIT could potentially be the technique enabling rapid portable and low-cost imaging solutions, but traditionally it results in poor quality blurry images because of the severe theoretical limitations.

Time-of-flight EIT can overcome all limitations and result in great improvement in spatial resolution, theoretically providing MRI-quality images with millisecond temporal resolution. The theory relies on the fact that if the current is injected in form of an ideal step function, within the conductive object the current spreads and different paths would take different times to arrive at an opposite electrode. By measuring the voltages at different times of arrival, it is possible to distinguish between the conductivities of all the above different paths, which theoretically will result in a clear high-resolution image. Although the technique is theoretically possible, in practice it was never performed because it is impossible to produce an ideal pulse delta function of a current, and there are additional distortions associated with wave propagation inside the complex conductive object.

The above challenges could be solved by employing temporally separated CHIRP excitation patterns (linear frequency modulation). This way of injecting the current is possible to produce in practice, and more importantly, would allow separation between the true time of arrival and all internal distortions within the object. Preliminary calculations showed that these CHIRP pulses would allow resulting images to have 1mm spatial resolution and 1 ms temporal resolution.

This will establish a completely new imaging technique with unique capabilities, which has the potential to revolutionise diagnostic medicine and perform life-saving changes in several areas of medical practice. In particular, this will disrupt neurology where there are no other alternative techniques for non-invasive imaging inside the human brain.

Photo by Shahadat Rahman on Unsplash