title: Evaluation of plaque composition by intravascular ultrasound "virtual histology": the impact of dense calcium on the measurement of necrotic tissue.
abstract: OBJECTIVE
  We aimed to evaluate if the co-localisation of calcium and necrosis in intravascular ultrasound virtual histology (IVUS-VH) is due to artefact, and whether this effect can be mathematically estimated.
  
  
  RESULTS
  We hypothesised that, in case calcium induces an artefactual coding of necrosis, any addition in calcium content would generate an artificial increment in the necrotic tissue. Stent struts were used to simulate the "added calcium". The change in the amount and in the spatial localisation of necrotic tissue was evaluated before and after stenting (n=17 coronary lesions) by means of a especially developed imaging software. The area of "calcium" increased from a median of 0.04 mm2 at baseline to 0.76 mm2 after stenting (p<0.01). In parallel the median necrotic content increased from 0.19 mm2 to 0.59 mm2 (p<0.01). The "added" calcium strongly predicted a proportional increase in necrosis-coded tissue in the areas surrounding the calcium-like spots (model R2=0.70; p<0.001).
  
  
  CONCLUSIONS
  Artificial addition of calcium-like elements to the atherosclerotic plaque led to an increase in necrotic tissue in virtual histology that is probably artefactual. The overestimation of necrotic tissue by calcium strictly followed a linear pattern, indicating that it may be amenable to mathematical correction.
authors.affiliation: Heart Institute, University of São Paulo Medical School, Brazil.
authors.forename: Fernando J R
authors.initials: FJ
authors.lastname: Sales
authors.forename: Breno A
authors.initials: BA
authors.lastname: Falcão
authors.forename: João L A
authors.initials: JL
authors.lastname: Falcão
authors.forename: Expedito E
authors.initials: EE
authors.lastname: Ribeiro
authors.forename: Marco A
authors.initials: MA
authors.lastname: Perin
authors.forename: Pedro E
authors.initials: PE
authors.lastname: Horta
authors.forename: André G
authors.initials: AG
authors.lastname: Spadaro
authors.forename: John A
authors.initials: JA
authors.lastname: Ambrose
authors.forename: Eulógio E
authors.initials: EE
authors.lastname: Martinez
authors.forename: Sergio S
authors.initials: SS
authors.lastname: Furuie
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Lemos
mesh_terms: D002114:Calcinosis / Q000000981:diagnostic imaging* / Q000473:pathology; D003198:Computer Simulation; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000473:pathology; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D058226:Plaque, Atherosclerotic / Q000000981:diagnostic imaging* / Q000473:pathology; D015203:Reproducibility of Results; D018084:Ultrasonography, Interventional / Q000379:methods*