title: Reducing the dose of CT of the paranasal sinuses: potential of an iterative reconstruction algorithm.
abstract: OBJECTIVE
  To evaluate the feasibility and image quality of low-dose CT of the paranasal sinuses using iterative reconstruction with adaptive-iterative dose reduction in three dimensions (AIDR 3D) in comparison with conventional image protocols of older scanner generations.
  
  
  METHODS
  Sinus CT scans of 136 patients were assessed retrospectively. Patients underwent CT either with low-dose settings (Protocol A: 80 kV, 30 mA s; Protocol B: 120 kV, 15 mA s or C: 80 kV, 90 mA s) reconstructed using AIDR 3D (Protocols A and B) or filtered back projection (FBP) (Protocol C) or with standard dose (Protocol D: 120 kV, 80 mA s) and FBP. Image quality was assessed in consensus by two blinded readers scoring the diagnostic image quality (from 1 = excellent to 5 = non-diagnostic) and conspicuity of important anatomic landmarks (from 0 = not visible to 2 = completely visible; maximum score of 16 points) as well as osseous structures (maximum score of 12 points). Dose-length product, effective dose (ED), CT dose index and scan length were retrieved for each scan and compared.
  
  
  RESULTS
  Mean ED could be lowered by 82% when using Protocol A. The best image quality was found using Protocol B (mean score = 2.1 ± 0.51). Conspicuity of relevant anatomic landmarks was best with Protocol A (mean score = 11.97 ± 1.88). Protocol B provided the highest conspicuity of osseous structures (mean score = 8.27 ± 1.58). Image noise was highest in images obtained using Protocol A.
  
  
  CONCLUSIONS
  AIDR 3D allows a significant dose reduction while maintaining a good diagnostic image quality and conspicuity of relevant anatomic structures.
authors.affiliation: Department of Radiology, Campus Benjamin Franklin, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Lars-Arne
authors.identifier: http://orcid.org/0000-0002-2250-5419
authors.initials: LA
authors.lastname: Schaafs
authors.affiliation: Department of Radiology, Campus Benjamin Franklin, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Lenk
authors.affiliation: Department of Radiology, Campus Benjamin Franklin, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Hamm
authors.affiliation: Department of Radiology, Campus Benjamin Franklin, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Stefan Markus
authors.initials: SM
authors.lastname: Niehues
mesh_terms: D000328:Adult; D000465:Algorithms; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D016477:Artifacts; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000706:statistics & numerical data; D021621:Imaging, Three-Dimensional / Q000379:methods / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D010256:Paranasal Sinuses / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000706:statistics & numerical data
keywords: computed tomography; dose reduction; head and neck; iterative reconstruction; low dose; paranasal sinus