title: Simulated cystic renal lesions: quantitative X-ray phase-contrast CT--an in vitro phantom study.
abstract: OBJECTIVE
  To determine if grating-based x-ray phase-contrast computed tomography (CT) can allow differentiation of simulated simple, protein-rich, hemorrhagic, and enhancing cystic renal lesions in an in vitro phantom.
  
  
  METHODS
  An in vitro phantom specifically designed to simulate simple, protein-rich, hemorrhagic, and enhancing renal cysts was scanned with an experimental grating-based phase-contrast CT setup consisting of a Talbot-Lau interferometer with a rotating anode x-ray tube and a single photon counting detector. Various combinations of serum and saline (100% and 0% to 0% and 100%), blood and saline, blood and serum (100% and 0% to 6.25% and 93.75% for both), and an iodinated contrast agent and saline (7.6-1.6 mg per milliliter of saline) were used to reproduce the chemical composition of the different types of cysts. A thickened solution of an iodinated contrast agent calibrated with a clinical multidetector CT scanner served as contrast agent-enhanced renal parenchyma (195 HU at 80 kVp, 400 mAs and 98 HU at 140 kVp, 200 mAs). Standard attenuation- and phase-contrast images were reconstructed from the raw projection data. Quantitative values for attenuation and phase contrast and image noise were determined. Contrast-to-noise ratios were calculated. Simulated lesions were assessed for visual differentiability by means of pairwise comparison of the attenuation- and phase-contrast images and both images simultaneously.
  
  
  RESULTS
  Attenuation-contrast imaging showed large differences in Hounsfield units with increasing concentrations of iodine (118.9 HU for 1.6 mg/mL vs 331.4 HU for 7.6 mg/mL). Values for phase-contrast imaging were substantially distinguishable for saline, serum, and blood (7.9, 23.7, and 52.8 HU, respectively). Both imaging modalities combined allowed differentiation of all four types of simulated cysts (100% saline, 100% serum, 100% blood, and 1.6-7.6 mg of iodine per milliliter of saline) with one imaging acquisition.
  
  
  CONCLUSIONS
  Grating-based phase-contrast CT allows differentiation of simulated simple, protein-rich, hemorrhagic, and enhancing renal cysts in an in vitro phantom through simultaneous assessment of their distinct attenuation- and phase-contrast signal.
authors.affiliation: From the Department of Radiology, Klinikum rechts der Isar, Technische Universität München, Ismaningerstr 22, 81675 Munich, Germany (A.A.F., D.M., E.J.R., P.B.N.); and Department of Physics and Institute of Medical Engineering, Technische Universität München, Garching, Germany (M.W., J.H., D.H., F.P.).
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Fingerle
authors.forename: Marian
authors.initials: M
authors.lastname: Willner
authors.forename: Julia
authors.initials: J
authors.lastname: Herzen
authors.forename: Daniela
authors.initials: D
authors.lastname: Münzel
authors.forename: Dieter
authors.initials: D
authors.lastname: Hahn
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Rummeny
authors.forename: Peter B
authors.initials: PB
authors.lastname: Noël
authors.forename: Franz
authors.initials: F
authors.lastname: Pfeiffer
mesh_terms: D006801:Humans; D052177:Kidney Diseases, Cystic / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D014961:X-Ray Diffraction / Q000295:instrumentation / Q000379:methods*