A Reconstruction Toolkit for Multichannel CT

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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.