title: How low can we go in contrast-enhanced CT imaging of the chest?: A dose-finding cadaver study using the model-based iterative image reconstruction approach.
abstract: OBJECTIVE
  Dose reduction may compromise patients because of a decrease of image quality. Therefore, the amount of dose savings in new dose-reduction techniques needs to be thoroughly assessed. To avoid repeated studies in one patient, chest computed tomography (CT) scans with different dose levels were performed in corpses comparing model-based iterative reconstruction (MBIR) as a tool to enhance image quality with current standard full-dose imaging.
  
  
  METHODS
  Twenty-five human cadavers were scanned (CT HD750) after contrast medium injection at different, decreasing dose levels D0-D5 and respectively reconstructed with MBIR. The data at full-dose level, D0, have been additionally reconstructed with standard adaptive statistical iterative reconstruction (ASIR), which represented the full-dose baseline reference (FDBR). Two radiologists independently compared image quality (IQ) in 3-mm multiplanar reformations for soft-tissue evaluation of D0-D5 to FDBR (-2, diagnostically inferior; -1, inferior; 0, equal; +1, superior; and +2, diagnostically superior). For statistical analysis, the intraclass correlation coefficient (ICC) and the Wilcoxon test were used.
  
  
  RESULTS
  Mean CT dose index values (mGy) were as follows: D0/FDBR = 10.1 ± 1.7, D1 = 6.2 ± 2.8, D2 = 5.7 ± 2.7, D3 = 3.5 ± 1.9, D4 = 1.8 ± 1.0, and D5 = 0.9 ± 0.5. Mean IQ ratings were as follows: D0 = +1.8 ± 0.2, D1 = +1.5 ± 0.3, D2 = +1.1 ± 0.3, D3 = +0.7 ± 0.5, D4 = +0.1 ± 0.5, and D5 = -1.2 ± 0.5. All values demonstrated a significant difference to baseline (P < .05), except mean IQ for D4 (P = .61). ICC was 0.91.
  
  
  CONCLUSIONS
  Compared to ASIR, MBIR allowed for a significant dose reduction of 82% without impairment of IQ. This resulted in a calculated mean effective dose below 1 mSv.
authors.affiliation: Department of Clinical Radiology, Hospital of the Ludwig-Maximilians-University of Munich, Downtown Campus, Nußbaumstr. 20, Munich 80336, Germany. Electronic address: fabian.mueck@med.uni-muenchen.de.
authors.forename: Fabian G
authors.initials: FG
authors.lastname: Mueck
authors.affiliation: Department of Clinical Radiology, Hospital of the Ludwig-Maximilians-University of Munich, Downtown Campus, Nußbaumstr. 20, Munich 80336, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Roesch
authors.affiliation: Department of Clinical Radiology, Hospital of the Ludwig-Maximilians-University of Munich, Downtown Campus, Nußbaumstr. 20, Munich 80336, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Scherr
authors.affiliation: Department of Forensic Medicine, Hospital of the Ludwig-Maximilians-University of Munich, Munich, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Fischer
authors.affiliation: Department of Clinical Radiology, Hospital of the Ludwig-Maximilians-University of Munich, Downtown Campus, Nußbaumstr. 20, Munich 80336, Germany.
authors.forename: Lucas
authors.initials: L
authors.lastname: Geyer
authors.affiliation: Department of Forensic Medicine, Hospital of the Ludwig-Maximilians-University of Munich, Munich, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Peschel
authors.affiliation: Department of Clinical Radiology, Hospital of the Ludwig-Maximilians-University of Munich, Downtown Campus, Nußbaumstr. 20, Munich 80336, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Maxien
authors.affiliation: University Center of Legal Medicine Lausanne-Geneva, University Hospital of Lausanne, Lausanne, Switzerland.
authors.forename: Silke
authors.initials: S
authors.lastname: Grabherr
authors.affiliation: Department of Clinical Radiology, Hospital of the Ludwig-Maximilians-University of Munich, Downtown Campus, Nußbaumstr. 20, Munich 80336, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wirth
mesh_terms: D002102:Cadaver; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013902:Radiography, Thoracic / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media
keywords: Computed tomography; adaptive statistical iterative reconstrunction; dose reduction; image quality; model based image reconstruction