title: Low-dose, wide-detector array thoracic aortic CT angiography using an iterative reconstruction technique results in improved image quality with lower noise and fewer artifacts.
abstract: BACKGROUND
  Iterative reconstruction techniques (IRTs) may improve image quality for low-dose imaging compared with filtered back projection (FBP) reconstruction.
  
  
  OBJECTIVE
  We compared the results of an IRT for low-dose thoracic aortic computed tomography (CT) imaging with those from FBP reconstruction.
  
  
  METHODS
  Data from 50 patients who underwent 256-slice CT for evaluation of the thoracic aorta were reconstructed with FBP and an IRT (iDose(4)) at 3 noise-reduction strengths (levels 2, 4, and 6). A blinded reader graded image quality (scale, 1-5; 5 = high diagnostic confidence) and the extent of shoulder artifact (scale, 1-5; 5 = no artifact) on all reconstructions. A second reader evaluated a subset of 20 cases to determine interreader and intrareader reproducibility. The mean and SD of attenuation were measured at 5 locations along the thoracic aorta and both subclavian arteries.
  
  
  RESULTS
  Image noise (SD of attenuation) improved with IRT relative to FBP (aorta: FBP, 31.4 ± 8.6 HU; IRT level 2, 25.1 ± 6.9 HU; level 4, 21.7 ± 6.2 HU; level 6, 17.2 ± 5.4 HU; P < 0.0001; subclavian arteries: FBP, 92.7 ± 34.6 HU; IRT level 2, 50.1 ± 17.1 HU; level 4, 48.9 ± 18.6 HU; level 6, 45.2 ± 19.2 HU; P < 0.0001), whereas mean attenuation was unchanged. Increasing image quality was observed in the aorta and through the shoulders as the contribution from IRT to the final images increased (P < 0.0001). Significant differences were noted between readers in image quality assessment of the aorta but not through the shoulders.
  
  
  CONCLUSIONS
  IRT is associated with reduced noise and shoulder artifact and allows for low-dose aortic CT imaging.
authors.affiliation: Division of Radiology, Imaging Institute, Cardiovascular Imaging, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH, USA.
authors.forename: Prabhakar
authors.initials: P
authors.lastname: Rajiah
authors.forename: Paul
authors.initials: P
authors.lastname: Schoenhagen
authors.forename: Dhruv
authors.initials: D
authors.lastname: Mehta
authors.forename: Thomas
authors.initials: T
authors.lastname: Ivanc
authors.forename: Michael
authors.initials: M
authors.lastname: Lieber
authors.forename: Kassem
authors.initials: K
authors.lastname: Soufan
authors.forename: Milind
authors.initials: M
authors.lastname: Desai
authors.forename: Scott D
authors.initials: SD
authors.lastname: Flamm
authors.forename: Sandra
authors.initials: S
authors.lastname: Halliburton
mesh_terms: D000465:Algorithms; D000792:Angiography / Q000379:methods*; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging*; D001018:Aortic Diseases / Q000000981:diagnostic imaging*; D001027:Aortography / Q000379:methods*; D016477:Artifacts; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*