Abdominal Radiology

, Volume 44, Issue 1, pp 355–361 | Cite as

Comparison of image noise and image quality between full-dose abdominal computed tomography scans reconstructed with weighted filtered back projection and half-dose scans reconstructed with improved sinogram-affirmed iterative reconstruction (SAFIRE*)

  • Stephen ChoyEmail author
  • Dennis Parhar
  • Kevin Lian
  • Heiko Schmiedeskamp
  • Luck Louis
  • Timothy O’Connell
  • Patrick McLaughlin
  • Savvas Nicolaou



To retrospectively compare the image noise, signal-to-noise ratio (SNR), and subjective image quality between CT images acquired with a dual-source, split-dose imaging protocol reconstructed at full and half doses with weighted filtered back projection (wFBP) and an improved sinogram-affirmed iterative reconstruction algorithm (SAFIRE*).


Fifty-three consecutive patients underwent contrast-enhanced CT of the abdomen using a standardized dual-source, single energy CT protocol. Half-dose images were retrospectively generated using data from one detector only. Full-dose datasets were reconstructed with wFBP, while half-dose datasets were reconstructed with wFBP and SAFIRE* strengths 1–5. Region of interest analysis was performed to assess SNR and noise. Diagnostic acceptability, subjective noise, and spatial resolution were graded on a 10-point scale by two readers. Statistical analysis was carried out with repeated measures analysis of variance, Wilcoxon signed rank test, and Cohen’s κ test.


With the increasing strengths of SAFIRE*, a progressive reduction in noise and increase in SNR (p < 0.01) was observed. There was a statistically significant decrease in objective noise and increase in SNR in half-dose SAFIRE* strength 4 and 5 reconstructions compared to full-dose reconstructions using wFBP (p < 0.01). Qualitative analysis revealed a progressive increase in diagnostic acceptability, decrease in subjective noise and increase in spatial resolution for half-dose images reconstructed with the increasing strengths of SAFIRE* (p < 0.01).


Half-dose CT images reconstructed with SAFIRE* at strength 4 and 5 have superior image quality compared to full-dose images reconstructed with wFBP. SAFIRE* potentially allows dose reductions in the order of 50% over wFBP.


Abdominal imaging Dual-source CT Sinogram-affirmed iterative reconstruction Radiation dose reduction 


Compliance with ethical standards

Conflict of interest

The University of British Columbia has a master research agreement with Siemens. Stephen Choy declares he has no conflict of interest. Dennis Parhar declares he has no conflict of interest. Kevin Lian declares he has no conflict of interest. Heiko Schmiedeskamp is an employee of Siemens Medical Solutions USA. Luck Louis declares he has no conflict of interest. Timothy O’Connell has received speaker fees from Siemens. Patrick McLaughlin declares he has no conflict of interest. Savvas Nicolaou declares he has no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Hospital institutional review board approval was obtained for this retrospective study. The need for informed consent was waived.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Radiology, Vancouver General HospitalUniversity of British ColumbiaVancouverCanada
  2. 2.Siemens Medical SolutionsMalvernUSA

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