title: Ex vivo characterization of pathologic fluids with quantitative phase-contrast computed tomography.
abstract: OBJECTIVE
  X-ray phase-contrast imaging (PCI) provides additional information beyond absorption characteristics by detecting the phase shift of the X-ray beam passing through material. The grating-based system works with standard polychromatic X-ray sources, promising a possible clinical implementation. PCI has been shown to provide additional information in soft-tissue samples. The aim of this study was to determine if ex vivo quantitative phase-contrast computed tomography (PCCT) may differentiate between pathologic fluid collections.
  
  
  METHODS
  PCCT was performed with the grating interferometry method. A protein serial dilution, human blood samples and 17 clinical samples of pathologic fluid retentions were imaged and correlated with clinical chemistry measurements. Conventional and phase-contrast tomography images were reconstructed. Phase-contrast Hounsfield Units (HUp) were used for quantitative analysis analogously to conventional HU. The imaging was analyzed using overall means, ROI values as well as whole-volume-histograms and vertical gradients. Contrast to noise ratios were calculated between different probes and between imaging methods.
  
  
  RESULTS
  HUp showed a very good linear correlation with protein concentration in vitro. In clinical samples, HUp correlated rather well with cell count and triglyceride content. PCI was better than absorption imaging at differentiating protein concentrations in the protein samples as well as at differentiating blood plasma from cellular components. PCI also allowed for differentiation of watery samples (such as lymphoceles) from pus.
  
  
  CONCLUSIONS
  Phase-contrast computed tomography is a promising tool for the differentiation of pathologic fluids that appear homogenous with conventional attenuation imaging.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Eberhard Karls Universität Tübingen, Hoppe-Seyler-Weg 3, 72076 Tuebingen, Germany. Electronic address: vivien.richter@med.uni-tuebingen.de.
authors.forename: Vivien
authors.initials: V
authors.lastname: Richter
authors.affiliation: Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany. Electronic address: marian.willner@ph.tum.de.
authors.forename: Marian S
authors.initials: MS
authors.lastname: Willner
authors.affiliation: Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany. Electronic address: john.henningsen@tum.de.
authors.forename: John
authors.initials: J
authors.lastname: Henningsen
authors.affiliation: Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany. Electronic address: lorenz.birnbacher@ph.tum.de.
authors.forename: Lorenz
authors.initials: L
authors.lastname: Birnbacher
authors.affiliation: Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany. Electronic address: mathias.marschner@ph.tum.de.
authors.forename: Mathias
authors.initials: M
authors.lastname: Marschner
authors.affiliation: Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany. Electronic address: julia.herzen@ph.tum.de.
authors.forename: Julia
authors.initials: J
authors.lastname: Herzen
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. Electronic address: melanie.kimm@tum.de.
authors.forename: Melanie A
authors.initials: MA
authors.lastname: Kimm
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. Electronic address: peter.noel@tum.de.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Noël
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. Electronic address: ernst.rummeny@tum.de.
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Rummeny
authors.affiliation: Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany. Electronic address: franz.pfeiffer@tum.de.
authors.forename: Franz
authors.initials: F
authors.lastname: Pfeiffer
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. Electronic address: alexander.fingerle@tum.de.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Fingerle
mesh_terms: D001769:Blood / Q000000981:diagnostic imaging; D001826:Body Fluids / Q000000981:diagnostic imaging*; D006801:Humans; D007368:Interferometry; D019047:Phantoms, Imaging; D011506:Proteins / Q000378:metabolism; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D011506:Proteins
keywords: Fluid imaging; Phase contrast CT; Protein imaging