A Reconstruction Toolkit for Multichannel CT

Currently, conventional Computed Tomographic (CT) imaging is still in a black and white (1 channel) era, just as it was with the first image Rontgen captured in 1895!

Conventional X-ray imaging entails a polychromatic X-ray source (i.e. with a full spectrum of energies) but with energy-indiscriminate detectors (registering a single grey-scale channel). However, technological breakthroughs in energy-sensitive detectors enable a new era of tomographic imaging in 'colours' (multiple channels). Each pixel of the energy-selective detector records a spectrum consisting of hundreds or thousands of energy channels. Currently available software only allows us to reconstruct each (noisy) channel independently in turn, which is a significant limitation. We need to unlock the power of next-generation correlative reconstruction methods for multi-channel tomography. Notably, the registered energy channels are mutually correlated, just like the red-green-blue (RGB) channels of the color image. Therefore, noise and other inaccuracies in spectral measurements can be treated holistically across the channels, leading to massive improvements in imaging quality (higher signal-to-noise ratio and resolution) in addition to fundamentally new opportunities such as spectroscopic imaging, i.e., direct decomposition into fundamental elements.

The overall goal of this CCP Software Flagship project is to expand upon existing single-channel image reconstruction software (already developed by the CCPi project) to enable sophisticated multi-channel correlative reconstruction methods. A novel Reconstruction Toolkit for Multichannel CT (RT-MCT) will be developed and become a part of the end-user data pipeline Savu (a modular Python-based platform for tomographic data processing developed at Diamond Light Source (DLS) at Harwell, UK). Three major imaging facilities are key collaborators and committed initial users of the RT-MCT: 1) Manchester X-ray Imaging Facility (MXIF) is a leader of laboratory-based X-ray CT imaging and has developed the unique multi-channel instrument "The Colour Bay" (cone-beam geometry scanner which uses HEXITEC hyper-spectral detectors); 2) A new national Neutron Imaging and Diffraction Facility (IMAT) at the ISIS pulsed neutron spallation source (Harwell). IMAT will take advantage of the neutron time-of-flight (TOF) measurement technique for effective energy discrimination into thousands of channels making this unique technique hyper-spectral; 3) Diamond Light Source (DLS), the national synchrotron facility at Harwell, has a number of imaging beamlines including I18 and I14, dedicated to X-ray fluorescence, X-ray spectroscopy and diffraction, all of which entail multi-channel data sets.

The main aim is to deliver the RT-MCT to these facilities to provide much more efficient data reconstruction and analysis. Several work packages are identified which constitute the RT-MCT, namely a) accurate mathematical modelling of multi-channel imaging; b) formulation of optimal reconstruction problems; c) efficient algorithm implementation and integration in existing software framework; d) deployment to facilities and use in proof-of-concept case studies.

Societal: This research will focus on improving spectral imaging through reconstruction software development which will revolutionise materials science analysis. The proposed project will ensure closer collaborations with other CCPs; especially the CCP PET/MR (hybrid imaging) and CCP-EM (electron microscopy) groups. At present X-ray Computed Tomography is used for innovative non-destructive inspection, analysis of new materials, and threat detection in airport security screening. Multichannel imaging will provide a sea-change in research capability providing faster and more accurate image analysis with chemical mapping overlay generated in parallel. The full potential of multispectral imaging can only be realised through the development of a software toolkit for end users, the RT-MCT. With accurate image analysis provided by the RT-MCT industrial connections have already led to new funded projects with coders from the University of Manchester (MXIF) accessing raw and metadata outputs and reconstruction expertise, for example writing code for Nikon X-ray scanner. Industrial impact will be enhanced through continual collaborations with members of the CCP network and Working Group: in collaboration with industrial network members. The following industrial companies and national organisations are active members of the CCP network and on the Working Group; Nikon Metrology, FEI, LaVision, Zeiss, Bruker, Deben, Rapiscan, Simpleware, Tessella and the BSI Group.

Economic: Industrial X-ray Inspection is worth in excess of $450M worldwide and emerging applications are driving new demand for CT inspection. We will maximise the impact to industry by: 1) extending our current collaborations with the equipment manufacturers Nikon Metrology, FEI, LaVision, Zeiss, Bruker, Deben, Rapiscan, Simpleware, Tessella and the BSI Group. We will focus on developing both the software, ensuring we are at the forefront of new technology. 2) The University will utilise its network of commercial partners as pathways to industrial impact, specifically in the oil & gas, nuclear and aerospace sectors through dedicated research institutes: BP International Centre for Advanced Materials (BP-ICAM), Dalton Nuclear Institute, Aerospace Research Institute. 3) Collaborate with the SME Spectral-X, established in early 2014 to commercialise colour CT imaging, to capture value from truly "game-changing'' developments.

Scientific: The outputs from this Flagship will assist some of the major national facilities (ISIS and DLS) and lab-based systems ensuring that the UK is at the forefront of developments in this new analytical capability. It will also utilise related infrastructures including compute clusters within STFC and in the regions (N8, Archer and Hartree Centre). Diamond Light Source (DLS) scientists and the hundreds of academic and industrial beamline users annually will greatly benefit from the RT-MCT methods and software applied to their experimental data produced on energy-dispersive X-ray spectroscopy and diffraction (I18, I14) beamlines. IMAT ISIS neutron facility will accommodate the Savu-packaged RT-MCT for all future users. MXIF where laboratory based colour imaging was pioneered and the RT-MCT will substantially reduce the amount of time required to process data, increasing the research capability of the instrument.

People: The retention and development skilled people able to work in multidisciplinary teams is not only essential to the future of the CCPi but also to develop the leaders of tomorrow. We will provide the postdoctoral researchers with opportunities to acquire and improve upon a wide range of technical and transferable skills, which will be of value both during this project, and in their subsequent careers. The PDRAs will benefit from working in a multidisciplinary research environment and we place a high priority on training our researchers in communication and engagement with end users of our research.