title: Inter-scan variability of coronary artery calcium scoring assessed on 64-multidetector computed tomography vs. dual-source computed tomography: a head-to-head comparison.
abstract: OBJECTIVE
  Coronary artery calcium (CAC) scoring has emerged as a tool for risk stratification and potentially for monitoring response to risk factor modification. Therefore, repeat measurements should provide robust results and low inter-scanner variability for allowing meaningful comparison. The purpose of this study was to investigate inter-scanner variability of CAC for Agatston, volume, and mass scores by head-to-head comparison using two different cardiac computed tomography scanners: 64-detector multislice CT (MSCT) and 64-slice dual-source CT (DSCT).
  
  
  RESULTS
  Thirty patients underwent CAC measurements on both 64-MSCT (GE LightSpeed XT scanner: 120 kV, 70 mAs, 2.5 mm slices) and 64-DSCT (Siemens Somatom Definition: 120 kV, 80 mAs, 3 mm slices) within <100 days (0-97). Retrospective intra-scan comparison revealed an excellent correlation. The excellent intra-scan (inter-observer) agreement was documented by narrow limits of agreement and a correlation coefficient of variation (COV) of r ≥ 0.99 (P < 0.001) for all CAC scores with a low COV for both scanners (64-MSCT/64-DSCT), i.e. Agatston (2.0/2.1%), mass (3.0/2.0%), and volume (4.7/3.9%). Inter-scanner comparison revealed larger Bland-Altman (BA) limits of agreement, despite high correlation (r ≥ 0.97) for all scores, with COV at 15.1, 21.6, and 44.9% for Agatston, mass, and volume scores. The largest BA limits were observed for volume scores (-1552.8 to 574.2), which was massively improved (-241.0 to 300.4, COV 11.5%) after reanalysing the 64-DSCT scans (Siemens) with GE software/workstation (while Siemens software/workstation does not allow cross-vendor analysis). Phantom measurements confirmed overestimation of volume scores by 'syngo Ca-Scoring' (Siemens) software which should therefore be reviewed (vendor has been notified).
  
  
  CONCLUSIONS
  Intra- and inter-scan agreement of CAC measurement in a given data set is excellent. Inter-scanner variability is reasonable, particularly for Agatston units in the clinically most relevant range <1000. The use of different software solutions has a greater influence particularly on volume scores than the use of different scanner types.
authors.affiliation: Department of Radiology, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, NUK C 32, CH-8091 Zurich, Switzerland.
authors.forename: Jelena R
authors.initials: JR
authors.lastname: Ghadri
authors.forename: Robert
authors.initials: R
authors.lastname: Goetti
authors.forename: Michael
authors.initials: M
authors.lastname: Fiechter
authors.forename: Aju P
authors.initials: AP
authors.lastname: Pazhenkottil
authors.forename: Silke M
authors.initials: SM
authors.lastname: Küest
authors.forename: Rene N
authors.initials: RN
authors.lastname: Nkoulou
authors.forename: Christina
authors.initials: C
authors.lastname: Windler
authors.forename: Ronny R
authors.initials: RR
authors.lastname: Buechel
authors.forename: Bernhard A
authors.initials: BA
authors.lastname: Herzog
authors.forename: Oliver
authors.initials: O
authors.lastname: Gaemperli
authors.forename: Christian
authors.initials: C
authors.lastname: Templin
authors.forename: Philipp A
authors.initials: PA
authors.lastname: Kaufmann
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002114:Calcinosis / Q000000981:diagnostic imaging*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards*