title: Acceptability of virtual unenhanced CT of the aorta as a replacement for the conventional unenhanced phase.
abstract: OBJECTIVE
  To evaluate whether virtual unenhanced (VU) computed tomography (CT) images generated of the aorta were of sufficient quality to replace the conventional unenhanced (CU) images.
  
  
  METHODS
  Forty-nine patients undergoing examination of the thoracic or abdominal aorta were examined using a dual-energy protocol. VU images were generated from the arterial phase images and compared to the CU images. Objective analysis was performed by drawing paired regions of interest (ROIs) within the thoracic and abdominal aorta and measuring the radiodensity in Hounsfield units attenuation within the ROIs. Subjective analysis was performed by two experienced readers evaluating the VU images in terms of noise, quality, calcium loss, and overall acceptability.
  
  
  RESULTS
  The attenuation was significantly higher in the VU images compared to the CU images within the thoracic aorta (p < 0.01) but not within the abdominal aorta (p = 0.15). Overall the VU images of the abdominal aorta were deemed acceptable as replacements for the CU images in 93% of cases. For the thoracic aorta, the VU images were deemed acceptable in only 12% of cases, primarily due to pulsation artefact.
  
  
  CONCLUSIONS
  VU images of the abdominal aorta are acceptable as replacements for the CU images in the vast majority of cases; however, they are not suitable as replacements for the CU images of the thoracic aorta.
authors.affiliation: Department of Radiology, Addenbrooke's Hospital, Cambridge, UK. nadeem.shaida@addenbrookes.nhs.uk
authors.forename: N
authors.initials: N
authors.lastname: Shaida
authors.forename: D J
authors.initials: DJ
authors.lastname: Bowden
authors.forename: T
authors.initials: T
authors.lastname: Barrett
authors.forename: E M
authors.initials: EM
authors.lastname: Godfrey
authors.forename: A
authors.initials: A
authors.lastname: Taylor
authors.forename: A P
authors.initials: AP
authors.lastname: Winterbottom
authors.forename: T C
authors.initials: TC
authors.lastname: See
authors.forename: D J
authors.initials: DJ
authors.lastname: Lomas
authors.forename: A S
authors.initials: AS
authors.lastname: Shaw
mesh_terms: D001012:Aorta, Abdominal / Q000000981:diagnostic imaging*; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging*; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D013927:Thrombosis / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media