title: Calcium scoring in unenhanced and enhanced CT data of the aorta-iliacal arteries: impact of image acquisition, reconstruction, and analysis parameter settings.
abstract: BACKGROUND
  Several studies have been published on the matter of abdominal aortic and iliac calcifications and the association to clinical entities such as diabetes mellitus and renal failure. However, comparing of these studies is questionable since quantification methods for atherosclerosis differ.
  
  
  OBJECTIVE
  To evaluate the effect of image acquisition settings, reconstruction parameters, and analysis methods on calcium quantification in the abdominal aorta.
  
  
  METHODS
  Calcium scores were retrospectively determined on standardized abdominal CT scans of 15 patients. Two researchers obtained calcium scores with 10 different lower thresholds (LT) (130, 145, 160, 175, 200, 300, 400, 500, 600, 1000) in CT scans with and without contrast enhancement, with slice thicknesses (ST) varying between 2.0-5.0 mm for the non-contrast-enhanced series and between 1.0-5.0 mm for the contrast-enhanced series. In addition calcium scores obtained with two convolution kernels (B10f, B20f) were compared. Inter-observer variability was calculated.
  
  
  RESULTS
  Calcium scoring at higher STs is overestimated compared to smaller STs and this effect was more pronounced with increasing calcium loads. Concerning the convolution kernel, scores obtained with kernel B10f were overestimated compared to kernel B20f. Increase of LT resulted in a decrease of the calcium score and scoring in contrast-enhanced series resulted in higher scores compared to non-contrast-enhanced series. These effects are more apparent in patients with higher calcium loads. Calcium scoring reproducibility with the reference standard is limited for the aorta-iliac trajectory, whereas scoring with the remaining settings is reproducible.
  
  
  CONCLUSIONS
  Scores obtained with different settings cannot be compared. The inter-observer reproducibility was limited using the reference standard and practical difficulties were substantial. Scoring with higher LT, ST, and contrast enhancement is faster and has less practical difficulties.
authors.affiliation: Department of Surgery, University Medical Center Rotterdam, Erasmus MC, Rotterdam, the Netherlands. nielskomen@hotmail.com
authors.forename: N
authors.initials: N
authors.lastname: Komen
authors.forename: P
authors.initials: P
authors.lastname: Klitsie
authors.forename: J J
authors.initials: JJ
authors.lastname: Hermans
authors.forename: W J
authors.initials: WJ
authors.lastname: Niessen
authors.forename: G J
authors.initials: GJ
authors.lastname: Kleinrensink
authors.forename: J
authors.initials: J
authors.lastname: Jeekel
authors.forename: J F
authors.initials: JF
authors.lastname: Lange
mesh_terms: D001012:Aorta, Abdominal / Q000737:chemistry* / Q000000981:diagnostic imaging*; D001027:Aortography; D002118:Calcium / Q000032:analysis*; D003287:Contrast Media; D006801:Humans; D007083:Iliac Artery / Q000737:chemistry* / Q000000981:diagnostic imaging*; D007089:Image Enhancement; D015588:Observer Variation; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D002118:Calcium