title: Reducing the radiation dose for low-dose CT of the paranasal sinuses using iterative reconstruction: feasibility and image quality.
abstract: OBJECTIVE
  To evaluate image quality of dose-reduced CT of the paranasal-sinus using an iterative reconstruction technique.
  
  
  METHODS
  In this study 80 patients (mean age: 46.9±18 years) underwent CT of the paranasalsinus (Siemens Definition, Forchheim, Germany), with either standard settings (A: 120 kV, 60 mAs) reconstructed with conventional filtered back projection (FBP) or with tube current-time product lowering of 20%, 40% and 60% (B: 48 mAs, C: 36 mAs and D: 24 mAs) using iterative reconstruction (n=20 each). Subjective image quality was independently assessed by four blinded observers using a semiquantitative five-point grading scale (1=poor, 5=excellent). Effective dose was calculated from the dose-length product. Mann-Whitney-U-test was used for statistical analysis.
  
  
  RESULTS
  Mean effective dose was 0.28±0.03 mSv(A), 0.23±0.02 mSv(B), 0.17±0.02 mSv(C) and 0.11±0.01 mSv(D) resulting in a maximum dose reduction of 60% with iterative reconstruction technique as compared to the standard low-dose CT. Best image quality was observed at 48 mAs (mean 4.8; p<0.05), whereas standard low-dose CT (A) and maximum dose reduced scans (D) showed no significant difference in subjective image quality (mean 4.37 (A) and 4.31 (B); p=0.72). Interobserver agreement was excellent (κ values 0.79-0.93).
  
  
  CONCLUSIONS
  As compared to filtered back projection, the iterative reconstruction technique allows for significant dose reduction of up to 60% for paranasal-sinus CT without impairing the diagnostic image quality.
authors.affiliation: Department of Diagnostic Radiology, University Hospital Freiburg, Hugstetter Str. 55, 79106 Freiburg, Germany. stefan.bulla@uniklinik-freiburg.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Bulla
authors.forename: Philipp
authors.initials: P
authors.lastname: Blanke
authors.forename: Frederike
authors.initials: F
authors.lastname: Hassepass
authors.forename: Tobias
authors.initials: T
authors.lastname: Krauss
authors.forename: Jan Thorsten
authors.initials: JT
authors.lastname: Winterer
authors.forename: Christine
authors.initials: C
authors.lastname: Breunig
authors.forename: Mathias
authors.initials: M
authors.lastname: Langer
authors.forename: Gregor
authors.initials: G
authors.lastname: Pache
mesh_terms: D000465:Algorithms; D001822:Body Burden; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010256:Paranasal Sinuses / Q000000981:diagnostic imaging*; 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; D012852:Sinusitis / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*