@phdthesis{Magkos2023,
  author    = {Magkos, Sotirios},
  title     = {Iterative reconstruction from under-sampled Computed Tomography data},
  doi       = {10.25932/publishup-57278},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-572789},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xxii, 74},
  year      = {2023},
  abstract  = {In X-ray computed tomography (XCT), an X-ray beam of intensity I0 is transmitted through an object and its attenuated intensity I is measured when it exits the object. The attenuation of the beam depends on the attenuation coefficients along its path. The attenuation coefficients provide information about the structure and composition of the object and can be determined through mathematical operations that are referred to as reconstruction. The standard reconstruction algorithms are based on the filtered backprojection (FBP) of the measured data. While these algorithms are fast and relatively simple, they do not always succeed in computing a precise reconstruction, especially from under-sampled data. Alternatively, an image or volume can be reconstructed by solving a system of linear equations. Typically, the system of equations is too large to be solved but its solution can be approximated by iterative methods, such as the Simultaneous Iterative Reconstruction Technique (SIRT) and the Conjugate Gradient Least Squares (CGLS). This dissertation focuses on the development of a novel iterative algorithm, the Direct Iterative Reconstruction of Computed Tomography Trajectories (DIRECTT). After its reconstruction principle is explained, its performance is assessed for real parallel- and cone-beam CT (including under-sampled) data and compared to that of other established algorithms. Finally, it is demonstrated how the shape of the measured object can be modelled into DIRECTT to achieve even better reconstruction results.},
  language  = {en}
}
@article{MagkosKupschBruno2020,
  author    = {Magkos, Sotirios and Kupsch, Andreas and Bruno, Giovanni},
  title     = {Direct iterative reconstruction of computed tomography trajectories reconstruction from limited number of projections with DIRECTT},
  series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  volume    = {91},
  journal   = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  number    = {10},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0034-6748},
  doi       = {10.1063/5.0013111},
  pages     = {8},
  year      = {2020},
  abstract  = {X-ray computed tomography has many applications in materials science and non-destructive testing. While the standard filtered back-projection reconstruction of the radiographic datasets is fast and simple, it typically fails in returning accurate results from missing or inconsistent projections. Among the alternative techniques that have been proposed to handle such data is the Direct Iterative REconstruction of Computed Tomography Trajectories (DIRECTT) algorithm. We describe a new approach to the algorithm, which significantly decreases the computational time while achieving a better reconstruction quality than that of other established algorithms.},
  language  = {en}
}
@article{MagkosKupschBruno2021,
  author    = {Magkos, Sotirios and Kupsch, Andreas and Bruno, Giovanni},
  title     = {Suppression of cone-beam artefacts with Direct Iterative Reconstruction Computed Tomography Trajectories (DIRECTT)},
  series = {Journal of imaging : open access journal},
  volume    = {7},
  journal   = {Journal of imaging : open access journal},
  number    = {8},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2313-433X},
  doi       = {10.3390/jimaging7080147},
  pages     = {9},
  year      = {2021},
  abstract  = {The reconstruction of cone-beam computed tomography data using filtered back-projection algorithms unavoidably results in severe artefacts. We describe how the Direct Iterative Reconstruction of Computed Tomography Trajectories (DIRECTT) algorithm can be combined with a model of the artefacts for the reconstruction of such data. The implementation of DIRECTT results in reconstructed volumes of superior quality compared to the conventional algorithms.},
  language  = {en}
}