title: Volumetric assessment of the carotid bifurcation: an alternative concept to stenosis grading.
abstract: BACKGROUND
  To design a volumetric method for the assessment of carotid atheromatosis (CA) based on computed tomography (CT) angiography and three-dimensional (3D) reconstructions; to analyze the accuracy and optimal threshold values to differentiate between equivalent degrees of severity by duplex scanning and CT angiography (two-dimensional maximum intensity projection [2D MIP]; internal carotid artery stenosis [ICS] <50%; ICS >50%); and to assess the method's suitability to detect progression of CA.
  
  
  METHODS
  
  
  
  METHODS
  suitability and accuracy of a new diagnostic method.
  
  
  METHODS
  90 carotid bifurcations (45 patients) were assessed with duplex scanning and CT angiography, and reevaluated after 12 ± 2 months follow-up. Determinations: Assessment of internal carotid artery (ICA) stenosis degree with duplex scanning and 2D MIP CT angiography projections. Volumetric assessment of carotid bifurcation by CT angiography (contrast volume [mm(3)] and density [Hounsfield units, H.U.] between 2-cm below and 1-cm above the anatomic bifurcation of the carotid artery [BifV], and its ratio with 1-cm segment of the common carotid artery [CCV]).
  
  
  METHODS
  descriptive statistics; intraobserver and interobserver agreement (Bland-Altman plot and intraclass correlation coefficient [ICC], accuracy of 3D volumetry and duplex scanning as referred to MIP 2D CT angiography as gold standard: sensitivity (Sens), specificity (Sp), kappa index, and receiver operating characteristic curves (ROCs).
  
  
  RESULTS
  Estimation of MIP 2D images (CT angiography) confirmed the findings of duplex scanning in 23 of 30 ICS <50% and 48 of 53 ICS >50% (Sens, 0.91; Sp, 0.77% kappa = 0.68). Three-dimensional volumetric assessment of carotid bifurcation showed an intraobserver and interobserver agreement with an ICC of 0.96 (95% confidence interval [CI], 0.904-0.985) and 0.94 (95% CI, 0.822-0.977), respectively. The BifV-to-CCV ratio was 5.2 ± 1.8 in the ICS <50% group versus 3.8 ± 1.3 in the ICS >50% group (P = 0.001). The optimal cutoff point of the BifV-to-CCV relationship was identified from the ROC curve in 4.1 (Sens, 0.75; Sp, 0.75; kappa, 0.46). At 12 months, a decrease of the average BifV with regard to the baseline value (475.45 [155.6] mm(3) × H.U. vs. 501.3 [171.9] mm(3) × H.U.; P = 0.04) was observed. CA progression was detected in 32 bifurcations (14 ICS <50%; 18 ICS> 50%), with a reduced bifurcation volume of 137.8 (71.4) mm(3) × H.U.; P < 0.001.
  
  
  CONCLUSIONS
  Volumetric assessment of carotid bifurcation is a new concept based on assessing plaque burden rather than its hemodynamic effect or maximum stenosis; thus, justifying its moderate accuracy with regard to ICS conventional ICA grading based on biplanar images. This method can be especially useful in plaque progression studies given its accuracy to detect minor changes in the arterial lumen.
authors.affiliation: Angiology and Vascular Surgery Unit, Health Research Institute La Fe, Valencia, Spain. Electronic address: miralles_manher@gva.es.
authors.forename: Manuel
authors.initials: M
authors.lastname: Miralles
authors.affiliation: Angiology and Vascular Surgery Unit, Health Research Institute La Fe, Valencia, Spain.
authors.forename: Manel
authors.initials: M
authors.lastname: Arrébola
authors.affiliation: Radiology Department, Health Research Institute La Fe, Valencia, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Bruguer
authors.affiliation: Neurology Department, Health Research Institute La Fe, Valencia, Spain.
authors.forename: Aida
authors.initials: A
authors.lastname: Lago
authors.affiliation: Angiology and Vascular Surgery Unit, Health Research Institute La Fe, Valencia, Spain.
authors.forename: Raúl
authors.initials: R
authors.lastname: Lara
mesh_terms: D019540:Area Under Curve; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging*; D016893:Carotid Stenosis / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional; D015588:Observer Variation; D058226:Plaque, Atherosclerotic; D011237:Predictive Value of Tests; D012372:ROC Curve; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D018616:Ultrasonography, Doppler, Duplex