title: Upgrade to iterative image reconstruction (IR) in abdominal MDCT imaging: a clinical study for detailed parameter optimization beyond vendor recommendations using the adaptive statistical iterative reconstruction environment (ASIR).
abstract: OBJECTIVE
  To compare the image quality of dose-reduced 64-row abdominal CT reconstructed at different levels of adaptive statistical iterative reconstruction (ASIR) to full-dose baseline examinations reconstructed with filtered back-projection (FBP) in a clinical setting and upgrade situation.
  
  
  METHODS
  Abdominal baseline examinations (noise index NI = 29; LightSpeed VCT XT, GE) were intra-individually compared to follow-up studies on a CT with an ASIR option (NI = 43; Discovery HD750, GE), n = 42. Standard-kernel images were calculated with ASIR blendings of 0 - 100 % in slice and volume mode, respectively. Three experienced radiologists compared the image quality of these 567 sets to their corresponding full-dose baseline examination (- 2: diagnostically inferior, - 1: inferior, 0: equal, + 1: superior, + 2: diagnostically superior). Furthermore, a phantom was scanned. Statistical analysis used the Wilcoxon - the Mann-Whitney U-test and the intra-class correlation (ICC).
  
  
  RESULTS
  The mean CTDIvol decreased from 19.7 ± 5.5 to 12.2 ± 4.7 mGy (p < 0.001). The ICC was 0.861. The total image quality of the dose-reduced ASIR studies was comparable to the baseline at ASIR 50 % in slice (p = 0.18) and ASIR 50 - 100 % in volume mode (p > 0.10). Volume mode performed 73 % slower than slice mode (p < 0.01).
  
  
  CONCLUSIONS
  After the system upgrade, the vendor recommendation of ASIR 50 % in slice mode allowed for a dose reduction of 38 % in abdominal CT with comparable image quality and time expenditure. However, there is still further dose reduction potential for more complex reconstruction settings.
authors.affiliation: Institut für klinische Radiologie, Ludwig-Maximilians-Universität München. fabian.mueck@campus.lmu.de
authors.forename: F G
authors.initials: FG
authors.lastname: Mueck
authors.forename: M
authors.initials: M
authors.lastname: Körner
authors.forename: M K
authors.initials: MK
authors.lastname: Scherr
authors.forename: L L
authors.initials: LL
authors.lastname: Geyer
authors.forename: Z
authors.initials: Z
authors.lastname: Deak
authors.forename: U
authors.initials: U
authors.lastname: Linsenmaier
authors.forename: M
authors.initials: M
authors.lastname: Reiser
authors.forename: S
authors.initials: S
authors.lastname: Wirth
mesh_terms: D000465:Algorithms; D003627:Data Interpretation, Statistical; D006801:Humans; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011860:Radiography, Abdominal / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*