Sporadic diffraction and absorption volumetric X-ray imaging

This project will bring exciting advances to X-ray imaging by revealing the true nature of materials buried in 3-dimensional scans. The main limitation of conventional X-ray absorption imaging is that the image forming signals are a function of the attenuation coefficient, which tells us almost nothing about the chemical or crystallographic structure of the object under inspection. However, it is well understood that if diffracted flux, rather than the transmitted X-rays, is collected then slice images may be reconstructed using similar algorithms to conventional computed tomography (CT). The measurement of the energy or wavelength of the diffracted X-rays together with their associated diffraction angles enables the calculation of crystallographic parameters to identify, for example, the material phase of a sample.

Scientists and engineers routinely measure diffracted flux from carefully prepared samples in instruments called diffractometers. Typically, this 'molecular fingerprinting' process uses relatively soft radiation and long inspection times of which both are impractical for security and in vivo diagnostic imaging. Despite significant efforts over the decades, there is little evidence of the 'gold standard' specificity and sensitivity achieved in laboratory settings being realised in time critical, commercially viable 3-dimensional imaging technologies. For example, the security screening industry has recognised the potential for X-ray diffraction as a 'gold standard' probe since the early 1990s. The challenge in this sector includes identifying powders, liquids, aerosols, and gels buried amongst the clutter of everyday objects in security scans of luggage. State-of-the-art CT spectroscopic scanners are limited fundamentally and are unable to deal adequately with homemade explosives.

A main limitation of using diffracted radiation is that the signals are often orders of magnitude weaker in comparison with the primary incident beam. This fundamental limitation leads to long inspection times i.e. minutes or hours per point measurement, which in general is impractical for imaging. We have previously demonstrated a focal construct geometry (FCG) method where a hollow or conical shell beam produces high-intensity patterns or caustics in the diffracted flux from a sample. The bright caustics enable high-speed measurements that can be deconvoluted to form depth-resolved sectional images. Our novel method enables spatial features much smaller than the diameter of the interrogating beam to be resolved accurately in the reconstructed images. In keeping with standard computed tomography, FCG tomography in absorption and diffraction both use similar reconstruction principles.

In this project, we propose reducing the total number of X-ray measurements and X-ray dose by more than 90% by applying sporadic sampling to FCG absorption/diffraction signals. We use a state-of-the-art flat panel X-ray source with multiple X-ray emission points optically coupled to energy resolving detectors. We treat the array of emitters as a virtual or spatially offset linear array (SOLA) to implement sporadic sampling independently of the minimum separation between emitter points (limited by the emitter physics) and to minimise crosstalk between measurements. We expect our method to enable the collection of diffraction and absorption signals at the same scan rate to realise depth-resolved material specific imaging. A successful demonstration of our method would establish a platform technology scalable in both X-ray energy and inspection space. This work will maintain the UK at the forefront of these unique and exciting scientific developments in security and diagnostic imaging.

The programme will deliver a novel scanning instrument to help realise exciting advances in X-ray imaging with an initial target within security and medical applications. Central to this unique UK led research is a novel and rapid way of collecting 'molecular fingerprints' buried in complex or cluttered X-ray scans.

Deployment of our technology would support the UK's counter terrorism strategy CONTEST through reduction in the risk to the UK, its citizens and overseas interests. Specifically, the technology will address a global security need to identify accurately and automatically contraband and threat materials. It will provide the basis for enhanced detection and identification of threats such as homemade explosives hidden in luggage. The attacks in Manchester and Parsons Green in 2017 demonstrated that homemade explosives are a weapon of choice for terrorists. In particular, the work will have impact for the following sectors of society.

>Travelling public will benefit from enhanced safety and security at travel hubs through more accurate detection of improvised explosive devices. In addition, their experience will improve through the reduction in security queues and hand searches; our technology will reduce false alarm rates.

>Society at large will benefit through the disruption in the transportation, and illegal import of unlawful controlled substances, such as cocaine, heroin, methamphetamines, and other illegal drugs. The abuse of opioids such as fentanyl has created an unprecedented international public health crisis in the US. Fentanyl is a powerful synthetic opioid that is similar to morphine but is 50 to 100 times more potent. For example, in 2017, around 50,000 Americans died from opioid overdoses. The international mail has been identified as a route for illicit opioid distribution. The drugs are commonly transported in nearly pure, powdered form enabling large-scale drug trafficking via small packages sent in the mail. The UK is following inexorably the US trend.

The programme will also deliver a basis for a novel and accurate, non-invasive clinical scanner. One application of such a scanner is to assess bone quality and provide an individualised fracture risk prediction. A significant beneficiary of this aspect will be the ageing population who present with an increasing risk of fragility fracture. In particular, the work will have impact for the following sectors.

>Elderly populations, as individuals will receive more accurate management of their fracture risk. The reduced times to diagnosis will relieve associated psychological stress.

>Patients receiving therapy for bone disease will have improved care through faster and more accurate diagnostic testing.

>The NHS spends >£2 billion pa on osteoporosis and hip fractures. This amount would be reduced significantly if accurate fracture assessment were possible. Further, rapid and more accurate diagnosis within the community would produce efficiency savings for GPs and hospitals.

The potential global R&D investment will contribute ultimately to the UK's economic growth. Halo X-ray Technology Ltd and Adaptix will assume a world lead in the development of this new technology. The successful award of this grant will help attract Innovate UK and private venture funding to develop further commercial innovation in these areas. The export opportunity for new products based on this development will be significant and add substantially to the UK economy. The work will also enhance the ability of the Science and Technology Facilities Council to create licence agreements for its detector systems to offset the taxpayers' contributions to scientific research within the UK.

>The young scientists employed will benefit from training within an exciting and growing research field providing a springboard for future careers in academia and or industry.

>The Universities will benefit through an expanded research base, new collaborations and networks.