title: Feasibility of coronary calcium and stent image subtraction using 320-detector row CT angiography.
abstract: BACKGROUND
  The reader confidence and diagnostic accuracy of coronary CT angiography (CCTA) can be compromised by the presence of calcified plaques and stents causing blooming artifacts. Compared to conventional invasive coronary angiography (ICA), this may cause an overestimation of stenosis severity leading to false-positive results. In a pilot study, we tested the feasibility of a new coronary calcium image subtraction algorithm in relation to reader confidence and diagnostic accuracy.
  
  
  METHODS
  Forty-three patients underwent clinically indicated ICA and CCTA using a 320-detector row CT. Median Agatston score was 510. Two data sets were reconstructed: a conventional CCTA (CCTAconv) and a subtracted CCTA (CCTAsub), where calcifications detected on noncontrast images were subtracted from the CCTA. Reader confidence and concordance with ICA for identification of >50% stenosis were recorded. We defined target segments on CCTAconv as motion-free coronary segments with calcification or stent and low reader confidence. The effect of CCTAsub was assessed. No approval from the ethics committee was required according to Danish law.
  
  
  RESULTS
  A total of 76 target segments were identified. The use of coronary calcium image subtraction improved the reader confidence in 66% of these segments. In target segments, specificity (86% vs 65%; P < .01) and positive predictive value (71% vs 51%, P = .03) were improved using CCTAsub compared to CCTAconv without loss in negative predictive value.
  
  
  CONCLUSIONS
  Our initial experience with coronary calcium image subtraction suggests that it is feasible and could lead to an improvement in reader confidence and diagnostic accuracy for identification of significant coronary artery disease.
authors.affiliation: Department of Cardiology, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, Copenhagen 2100, Denmark. Electronic address: mck601@alumni.ku.dk.
authors.forename: Andreas
authors.initials: A
authors.lastname: Fuchs
authors.affiliation: Department of Cardiology, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, Copenhagen 2100, Denmark.
authors.forename: J Tobias
authors.initials: JT
authors.lastname: Kühl
authors.affiliation: National Heart Lung and Blood Institute, National Institute of Health, Bethesda, MD, USA.
authors.forename: Marcus Y
authors.initials: MY
authors.lastname: Chen
authors.affiliation: Department of Cardiology, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, Copenhagen 2100, Denmark.
authors.forename: Steffen
authors.initials: S
authors.lastname: Helqvist
authors.affiliation: Toshiba Medical Visualization Systems Europe, Edinburgh, United Kingdom.
authors.forename: Marco
authors.initials: M
authors.lastname: Razeto
authors.affiliation: Toshiba Medical Systems Corporation, Otawara, Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Arakita
authors.affiliation: Toshiba Medical Systems Corporation, Otawara, Japan.
authors.forename: Chloe
authors.initials: C
authors.lastname: Steveson
authors.affiliation: National Heart Lung and Blood Institute, National Institute of Health, Bethesda, MD, USA.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Arai
authors.affiliation: Department of Cardiology, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, Copenhagen 2100, Denmark; Department of Radiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Klaus F
authors.initials: KF
authors.lastname: Kofoed
mesh_terms: D000368:Aged; D015901:Angiography, Digital Subtraction; D016477:Artifacts; D017023:Coronary Angiography / Q000379:methods*; D023921:Coronary Stenosis / Q000000981:diagnostic imaging* / Q000628:therapy; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D003718:Denmark; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D062645:Percutaneous Coronary Intervention / Q000295:instrumentation*; D010865:Pilot Projects; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D015607:Stents; D061205:Vascular Calcification / Q000000981:diagnostic imaging* / Q000628:therapy
keywords: Angiography; CCTA; CT; Coronary; Subtraction