title: Sinogram affirmed iterative reconstruction in head CT: improvement of objective and subjective image quality with concomitant radiation dose reduction.
abstract: OBJECTIVE
  Iterative reconstruction has recently been revisited as a promising concept for substantial CT dose reduction. The purpose of this study was to assess the potential benefit of sinogram affirmed iterative reconstruction (SAFIRE) in head CT by comparing objective and subjective image quality at reduced tube current with standard dose filtered back projection (FBP).
  
  
  METHODS
  Non-contrast reduced dose head CT (255 mAs, CTDIvol 47.8 mGy) was performed in thirty consecutive patients and reconstructed with SAFIRE and FBP. Images were assessed in terms of quantitative and qualitative image quality and compared with FBP of standard dose acquisitions (320 mAs, CTDI vol 59.7 mGy).
  
  
  RESULTS
  In reduced dose CT examinations, use of SAFIRE versus FBP resulted in 47% increase in contrast-to-noise ratio (CNR) (2.49 vs. 1.69; p<0.0001). While reduction of tube current was associated with 13% decrease in CNR, quantitative degradation of image quality at lower dose was more than compensated through SAFIRE (2.49 vs. 1.96; p=0.0004). Objective measurements of image sharpness were comparable between FBP and SAFIRE reconstructions (575.9 ± 74.1 vs. 583.4 ± 74.7 change in HU/Pixel; p=0.28). Compared to standard dose FBP, subjective grading of noise as well as overall image quality scores were significantly improved when SAFIRE was used in reduced dose exams (1.3 vs. 1.6, p=0.006; 1.3 vs. 1.7, p=0.026).
  
  
  CONCLUSIONS
  At 20% dose reduction, reconstruction of head CT by SAFIRE provides above standard objective and subjective image quality, suggesting potential for more vigorous dose savings in neuroradiology CT applications.
authors.affiliation: Department of Diagnostic und Interventional Neuroradiology, Hoppe-Seyler-Straße 3, 72076 Tübingen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Korn
authors.forename: B
authors.initials: B
authors.lastname: Bender
authors.forename: M
authors.initials: M
authors.lastname: Fenchel
authors.forename: D
authors.initials: D
authors.lastname: Spira
authors.forename: C
authors.initials: C
authors.lastname: Schabel
authors.forename: C
authors.initials: C
authors.lastname: Thomas
authors.forename: T
authors.initials: T
authors.lastname: Flohr
authors.forename: C D
authors.initials: CD
authors.lastname: Claussen
authors.forename: R
authors.initials: R
authors.lastname: Bhadelia
authors.forename: U
authors.initials: U
authors.lastname: Ernemann
authors.forename: H
authors.initials: H
authors.lastname: Brodoefel
mesh_terms: D000328:Adult; D000465:Algorithms; D001927:Brain Diseases / Q000175:diagnosis*; D006259:Craniocerebral Trauma / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; 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; D014057:Tomography, X-Ray Computed
keywords: Head CT; Image quality; Iterative reconstruction