title: On the relative performance of edge illumination x-ray phase-contrast CT and conventional, attenuation-based CT.
abstract: OBJECTIVE
  This article is aimed at comparing edge illumination (EI) x-ray phase contrast computed tomography (PCT) and conventional (attenuation-based) computed tomography (CT), based on their respective contrast and noise transfer.
  
  
  METHODS
  The noise in raw projections obtained with EI PCT is propagated through every step of the data processing, including phase retrieval and tomographic reconstruction, leading to a description of the noise in the reconstructed phase tomograms. This is compared to the noise in corresponding attenuation tomograms obtained with CT. Specifically, a formula is derived that allows evaluating the relative performance of both modalities on the basis of their contrast-to-noise ratio (CNR), for a variety of experimental parameters.
  
  
  RESULTS
  The noise power spectra of phase tomograms are shifted towards lower spatial frequencies, leading to a fundamentally different noise texture. The relative performance of EI PCT and CT, in terms of their CNR, is linked to spatial resolution: the CNR in phase tomograms is generally superior to that in attenuation tomograms for higher spatial resolutions (tens to hundreds of μm), but inferior for lower spatial resolutions (hundreds of μm to mm).
  
  
  CONCLUSIONS
  These results imply that EI PCT could outperform CT in applications for which high spatial resolutions are key, e.g., small animal or specimen imaging.
authors.affiliation: Department of Medical Physics and Bioengineering, University College London, London, WC1E 6BT, UK.
authors.forename: Charlotte Klara
authors.initials: CK
authors.lastname: Hagen
authors.affiliation: Department of Medical Physics and Bioengineering, University College London, London, WC1E 6BT, UK.
authors.forename: Paul Claude
authors.initials: PC
authors.lastname: Diemoz
authors.affiliation: Department of Medical Physics and Bioengineering, University College London, London, WC1E 6BT, UK.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Olivo
mesh_terms: D000818:Animals; D008027:Light; D008029:Lighting; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed; D014965:X-Rays
keywords: computed tomography; phase-contrast imaging; x-ray imaging