title: Incidental Findings in Abdominal Dual-Energy Computed Tomography: Correlation Between True Noncontrast and Virtual Noncontrast Images Considering Renal and Liver Cysts and Adrenal Masses.
abstract: OBJECTIVE
  To assess correlation between attenuation measurements of incidental findings in abdominal second generation dual-energy computed tomography (CT) on true noncontrast (TNC) and virtual noncontrast (VNC) images.
  
  
  METHODS
  Sixty-three patients underwent arterial dual-energy CT (Somatom Definition Flash, Siemens; pitch factor, 0.75-1.0; gantry rotation time, 0.28 seconds) after endovascular aneurysm repair, consisting of a TNC single energy CT scan (collimation, 128 × 0.6 mm; 120 kVp) and a dual-energy arterial phase scan (collimation, 32 × 0.6 mm, 140 and 100 kVp; blended, 120 kVp data set). Attenuation measurements in Hounsfield units (HU) of liver parenchyma and incidental findings like renal and hepatic cysts and adrenal masses on TNC and VNC images were done by drawing regions of interest. Statistical analysis was performed by paired t test and Pearson correlation.
  
  
  RESULTS
  Incidental findings were detected in 56 (89%) patients. There was excellent correlation for both renal (n = 40) and hepatic cysts (n = 12) as well as adrenal masses (n = 6) with a Pearson correlation of 0.896, 0.800, and 0.945, respectively, and mean attenuation values on TNC and VNC images of 10.6 HU ± 12.8 versus 5.1 HU ± 17.5 (attenuation value range from -8.8 to 59.1 HU vs -11.8 to 73.4 HU), 6.4 HU ± 5.8 versus 6.3 HU ± 4.6 (attenuation value range from 2.0 to 16.2 HU vs -3.0 to 15.9 HU), and 12.8 HU ± 11.2 versus 12.4 HU ± 10.2 (attenuation value range from -2.3 to 27.5 HU vs -2.2 to 23.6 HU), respectively. As proof of principle, liver parenchyma measurements also showed excellent correlation between TNC and VNC (n = 40) images with a Pearson correlation of 0.839 and mean attenuation values on TNC and VNC images of 47.2 HU ± 10.5 versus 43.8 HU ± 8.7 (attenuation value range from 21.9 to 60.2 HU vs 4.5 to 65.3 HU).
  
  
  CONCLUSIONS
  In conclusion, attenuation measurements of incidental findings like renal cysts or adrenal masses on TNC and VNC images derived from second generation dual-energy CT scans show excellent correlation providing considerable dose savings, favorable for future application in clinical routine.
authors.affiliation: From the *Department of Radiology, University Hospital of Cologne, Cologne; †Department of Diagnostic and Interventional Radiology, Medical Faculty, University of Duesseldorf, Duesseldorf; ‡Institute of Medical Statistics, Informatics and Epidemiology, University Hospital of Cologne, Cologne; and §Department of Radiology, City Hospital Hanau, Hanau, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Slebocki
authors.forename: Bastian
authors.initials: B
authors.lastname: Kraus
authors.forename: De-Hua
authors.initials: DH
authors.lastname: Chang
authors.forename: Martin
authors.initials: M
authors.lastname: Hellmich
authors.forename: David
authors.initials: D
authors.lastname: Maintz
authors.forename: Christopher
authors.initials: C
authors.lastname: Bangard
mesh_terms: D000307:Adrenal Gland Diseases; D000311:Adrenal Glands / Q000000981:diagnostic imaging; D000368:Aged; D000369:Aged, 80 and over; D003560:Cysts / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D033162:Incidental Findings; D007668:Kidney / Q000000981:diagnostic imaging; D007674:Kidney Diseases / Q000000981:diagnostic imaging*; D008099:Liver / Q000000981:diagnostic imaging; D008107:Liver Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011860:Radiography, Abdominal / Q000379:methods*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014584:User-Computer Interface