title: Tin-filter enhanced dual-energy-CT: image quality and accuracy of CT numbers in virtual noncontrast imaging.
abstract: OBJECTIVE
  To measure and compare the objective image quality of true noncontrast (TNC) images with virtual noncontrast (VNC) images acquired by tin-filter-enhanced, dual-source, dual-energy computed tomography (DECT) of upper abdomen.
  
  
  METHODS
  Sixty-three patients received unenhanced abdominal CT and enhanced abdominal DECT (100/140 kV with tin filter) in portal-venous phase. VNC images were calculated from the DECT datasets using commercially available software. The mean attenuation of relevant tissues and image quality were compared between the TNC and VNC images. Image quality was rated objectively by measuring image noise and the sharpness of object edges using custom-designed software. Measurements were compared using Student two-tailed t-test. Correlation coefficients for tissue attenuation measurements between TNC and VNC were calculated and the relative deviations were illustrated using Bland-Altman plots.
  
  
  RESULTS
  Mean attenuation differences between TNC and VNC (HUTNC - HUVNC) image sets were as follows: right liver lobe -4.94 Hounsfield units (HU), left liver lobe -3.29 HU, vena cava -2.19 HU, spleen -7.46 HU, pancreas 1.29 HU, fat -11.14 HU, aorta 1.29 HU, bone marrow 36.83 HU (all P < .05); right kidney 0.46 HU, left kidney 0.56 HU, vena portae -0.48 HU and muscle -0.62 HU (nonsignificant). Good correlations between VNC and TNC series were observed for liver, vena portae, kidneys, pancreas, muscle and bone marrow (Pearson's correlation coefficient ≥0.75). Mean image noise was significantly higher in TNC images (P < .0001). Measurements of edge sharpness revealed no significant differences between VNC and TNC images (P = .19).
  
  
  CONCLUSIONS
  The Hounsfield units in VNC images closely resemble TNC images in the majority of the organs of the upper abdomen (kidneys, liver, pancreas). In spleen and fat, Hounsfield numbers in VNC images are tend to be higher than in TNC images. VNC images show a low image noise and satisfactory edge sharpness. Other criteria of image quality and the depiction of certain lesions need to be evaluated additionally.
authors.affiliation: Department of Radiology, Diagnostic and Interventional Radiology, Hoppe-Seyler-Str. 3, 72076 Tuebingen, Germany. sascha.kaufmann@med.uni-tuebingen.de
authors.forename: Sascha
authors.initials: S
authors.lastname: Kaufmann
authors.forename: Alexander
authors.initials: A
authors.lastname: Sauter
authors.forename: Daniel
authors.initials: D
authors.lastname: Spira
authors.forename: Sergios
authors.initials: S
authors.lastname: Gatidis
authors.forename: Dominik
authors.initials: D
authors.lastname: Ketelsen
authors.forename: Martin
authors.initials: M
authors.lastname: Heuschmid
authors.forename: Claus D
authors.initials: CD
authors.lastname: Claussen
authors.forename: Christoph
authors.initials: C
authors.lastname: Thomas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods; D011860:Radiography, Abdominal / Q000379:methods*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014001:Tin; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014462:Ultrafiltration / Q000379:methods*; D014584:User-Computer Interface
chemical_list: D014001:Tin