title: Incidental adrenal lesions detected on enhanced abdominal dual-energy CT: can the diagnostic workup be shortened by the implementation of virtual unenhanced images?
abstract: OBJECTIVE
  To determine whether post-processing of the data from portal-phase enhanced dual-energy CT (DECT), with or without the addition of a late enhanced phase acquisition, may enable characterization of adrenal lesions without the need for acquisition of pre-contrast images.
  
  
  METHODS
  Twenty-two patients with 24 adrenal lesions underwent unenhanced, venous and delayed phase DECT. Of these lesions, 20 were found to be adrenal adenomas, on the basis of histopathology, unenhanced attenuation values between 0 and -10 HU, or stability over at least 6 months. For all 24 lesions, true and virtual unenhanced attenuation values were measured based on the data of the portal (VNCp) and the delayed (VNCd) DECT acquisition. The absolute washout values based on the true non-contrast (TNC) and the VNCp and VNCd image series were also measured. The washout was also calculated based on the iodine concentration measured from both contrast-enhanced acquisitions.
  
  
  RESULTS
  Mean virtual unenhanced attenuation values of all lesions calculated from the portal phase images was 12.6 HU, and was 4.02 HU higher than the values based on true unenhanced images (p=0.020). Washout values calculated from virtual unenhanced attenuation based on the VNCp were also significantly different (p=0.0304) while those calculated from VNCd and from iodine concentration correlated with the corresponding values based on the true unenhanced values (p>0.999).
  
  
  CONCLUSIONS
  Our data indicate that attenuation values of adrenal adenomas based on virtual unenhanced images are significantly higher than those obtained with true unenhanced images. An incidental adrenal lesion with a virtual unenhanced attenuation lower than 10 HU can thus be safely characterized as an adenoma.
authors: Geneva University Hospital, Department of Imaging and Medical Information Sciences, Division of Radiology, Rue Gabrielle-Perret-Gentil 4, 1211 Genève 4, Switzerland. Electronic address: diomidis.botsikas@hcuge.ch.
authors: Diomidis
authors: D
authors: Botsikas
authors: Geneva University Hospital, Department of Surgery, Division of Thoracic Surgery, Rue Gabrielle-Perret-Gentil 4, 1211 Genève 4, Switzerland. Electronic address: Frederic.Triponez@hcuge.ch.
authors: Frederic
authors: F
authors: Triponez
authors: Geneva University Hospital, Department of Imaging and Medical Information Sciences, Division of Radiology, Rue Gabrielle-Perret-Gentil 4, 1211 Genève 4, Switzerland. Electronic address: sana.boudabbous@hcuge.ch.
authors: Sana
authors: S
authors: Boudabbous
authors: Geneva University Hospital, Department of Imaging and Medical Information Sciences, Division of Radiology, Rue Gabrielle-Perret-Gentil 4, 1211 Genève 4, Switzerland. Electronic address: catrina.hansen@hcuge.ch.
authors: Catrina
authors: C
authors: Hansen
authors: Geneva University Hospital, Department of Imaging and Medical Information Sciences, Division of Radiology, Rue Gabrielle-Perret-Gentil 4, 1211 Genève 4, Switzerland. Electronic address: christoph.becker@hcuge.ch.
authors: Christoph D
authors: CD
authors: Becker
authors: Geneva University Hospital, Department of Imaging and Medical Information Sciences, Division of Radiology, Rue Gabrielle-Perret-Gentil 4, 1211 Genève 4, Switzerland. Electronic address: xavier.montet@hcuge.ch.
authors: Xavier
authors: X
authors: Montet
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging*; D018246:Adrenocortical Adenoma / Q000000981:diagnostic imaging*; D000368:Aged; D003287:Contrast Media; D005260:Female; D006801:Humans; D033162:Incidental Findings; D008297:Male; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media
keywords: Adrenal incidentalomas; Adrenal lesion characterization; Dual-energy CT; Virtual unenhanced images