title: Submillisievert coronary calcium quantification using model-based iterative reconstruction: A within-patient analysis.
abstract: OBJECTIVE
  To determine the effect of model-based iterative reconstruction (IR) on coronary calcium quantification using different submillisievert CT acquisition protocols.
  
  
  METHODS
  Twenty-eight patients received a clinically indicated non contrast-enhanced cardiac CT. After the routine dose acquisition, low-dose acquisitions were performed with 60%, 40% and 20% of the routine dose mAs. Images were reconstructed with filtered back projection (FBP), hybrid IR (HIR) and model-based IR (MIR) and Agatston scores, calcium volumes and calcium mass scores were determined.
  
  
  RESULTS
  Effective dose was 0.9, 0.5, 0.4 and 0.2mSv, respectively. At 0.5 and 0.4mSv, differences in Agatston scores with both HIR and MIR compared to FBP at routine dose were small (-0.1 to -2.9%), while at 0.2mSv, differences in Agatston scores of -12.6 to -14.6% occurred. Reclassification of risk category at reduced dose levels was more frequent with MIR (21-25%) than with HIR (18%).
  
  
  CONCLUSIONS
  Radiation dose for coronary calcium scoring can be safely reduced to 0.4mSv using both HIR and MIR, while FBP is not feasible at these dose levels due to excessive noise. Further dose reduction can lead to an underestimation in Agatston score and subsequent reclassification to lower risk categories. Mass scores were unaffected by dose reductions.
authors: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands. Electronic address: a.m.denharder@umcutrecht.nl.
authors: Annemarie M
authors: AM
authors: den Harder
authors: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Jelmer M
authors: JM
authors: Wolterink
authors: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Martin J
authors: MJ
authors: Willemink
authors: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Arnold M R
authors: AMR
authors: Schilham
authors: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Pim A
authors: PA
authors: de Jong
authors: Department of Radiology, Erasmus Medical Center, Rotterdam, The Netherlands.
authors: Ricardo P J
authors: RPJ
authors: Budde
authors: Department of Cardiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Hendrik M
authors: HM
authors: Nathoe
authors: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Ivana
authors: I
authors: Išgum
authors: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Tim
authors: T
authors: Leiner
mesh_terms: D000465:Algorithms; D002114:Calcinosis / Q000000981:diagnostic imaging* / Q000473:pathology; D017023:Coronary Angiography / Q000379:methods; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D019047:Phantoms, Imaging; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: Cardiac; Computed tomography; Coronary artery calcification; Iterative reconstruction