title: The impact of CT radiation dose reduction and iterative reconstruction algorithms from four different vendors on coronary calcium scoring.
abstract: OBJECTIVE
  To analyse the effects of radiation dose reduction and iterative reconstruction (IR) algorithms on coronary calcium scoring (CCS).
  
  
  METHODS
  Fifteen ex vivo human hearts were examined in an anthropomorphic chest phantom using computed tomography (CT) systems from four vendors and examined at four dose levels using unenhanced prospectively ECG-triggered protocols. Tube voltage was 120 kV and tube current differed between protocols. CT data were reconstructed with filtered back projection (FBP) and reduced dose CT data with IR. CCS was quantified with Agatston scores, calcification mass and calcification volume. Differences were analysed with the Friedman test.
  
  
  RESULTS
  Fourteen hearts showed coronary calcifications. Dose reduction with FBP did not significantly change Agatston scores, calcification volumes and calcification masses (P > 0.05). Maximum differences in Agatston scores were 76, 26, 51 and 161 units, in calcification volume 97, 27, 42 and 162 mm(3), and in calcification mass 23, 23, 20 and 48 mg, respectively. IR resulted in a trend towards lower Agatston scores and calcification volumes with significant differences for one vendor (P < 0.05). Median relative differences between reference FBP and reduced dose IR for Agatston scores remained within 2.0-4.6%, 1.0-5.3%, 1.2-7.7% and 2.6-4.5%, for calcification volumes within 2.4-3.9%, 1.0-5.6%, 1.1-6.4% and 3.7-4.7%, for calcification masses within 1.9-4.1%, 0.9-7.8%, 2.9-4.7% and 2.5-3.9%, respectively. IR resulted in increased, decreased or similar calcification masses.
  
  
  CONCLUSIONS
  CCS derived from standard FBP acquisitions was not affected by radiation dose reductions up to 80%. IR resulted in a trend towards lower Agatston scores and calcification volumes.
  
  
  CONCLUSIONS
  In this ex vivo study, radiation dose could be reduced by 80% for coronary calcium scoring. Iterative reconstruction resulted in a trend towards lower Agatston scores and calcification volumes. Caution should be taken for coronary calcium scoring with iterative reconstruction.
authors.affiliation: Department of Radiology, Utrecht University Medical Center, P.O. Box 85500, E01.132, 3508 GA, Utrecht, The Netherlands, m.willemink@umcutrecht.nl.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Willemink
authors.forename: Richard A P
authors.initials: RA
authors.lastname: Takx
authors.forename: Pim A
authors.initials: PA
authors.lastname: de Jong
authors.forename: Ricardo P J
authors.initials: RP
authors.lastname: Budde
authors.forename: Ronald L A W
authors.initials: RL
authors.lastname: Bleys
authors.forename: Marco
authors.initials: M
authors.lastname: Das
authors.forename: Joachim E
authors.initials: JE
authors.lastname: Wildberger
authors.forename: Mathias
authors.initials: M
authors.lastname: Prokop
authors.forename: Nico
authors.initials: N
authors.lastname: Buls
authors.forename: Johan
authors.initials: J
authors.lastname: de Mey
authors.forename: Arnold M R
authors.initials: AM
authors.lastname: Schilham
authors.forename: Tim
authors.initials: T
authors.lastname: Leiner
mesh_terms: D000465:Algorithms; D002102:Cadaver; D002114:Calcinosis / Q000000981:diagnostic imaging* / Q000378:metabolism; D002118:Calcium / Q000032:analysis*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000378:metabolism; D003331:Coronary Vessels / Q000737:chemistry*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D002118:Calcium