title: New CT index to quantify arterial obstruction in pulmonary embolism: comparison with angiographic index and echocardiography.
abstract: OBJECTIVE
  This study was designed to define and evaluate a specific index to quantify arterial obstruction with helical CT in acute pulmonary embolism.
  
  
  METHODS
  Fifty-four patients (mean age, 56 years) with proven pulmonary emboli among 158 consecutive patients, who had undergone both CT and pulmonary angiography for clinically suspected pulmonary embolism, were eligible for the study. The CT obstruction index was defined as (n. d) (n, value of the proximal clot site, equal to the number of segmental branches arising distally; d, degree of obstruction scored as partial obstruction [value of 1] or total obstruction [value of 2]). We compared the CT obstruction index with pulmonary arterial obstruction on angiography (assessed by the Miller index), using linear regression, and correlated it with findings on echocardiography. Interobserver variability was determined for both CT and pulmonary angiography indexes.
  
  
  RESULTS
  The CT obstruction index (29% +/- 17%) and the Miller index (43% +/- 25%) were well correlated (r = 0.867, p < 0.0001) with an excellent concordance between investigators for both the CT index (r = 0.944, p < 0.0001) and the Miller index (r = 0.904, p < 0.0001). A CT obstruction index greater than 40% identified more than 90% of patients with right ventricular dilatation.
  
  
  CONCLUSIONS
  The degree of arterial obstruction in pulmonary embolism may be quantified by a specific CT index that appears reproducible and highly correlated to the previously described index with pulmonary angiography. Further evaluations are needed to investigate the usefulness of the CT obstruction index for stratification of patient risk and determining therapeutic options.
authors.affiliation: Department of Radiology, University René Descartes-Paris V, Ambroise Paré Hospital, 9 Avenue Charles De Gaulle, 92104 Boulogne, France.
authors.forename: S D
authors.initials: SD
authors.lastname: Qanadli
authors.forename: M
authors.initials: M
authors.lastname: El Hajjam
authors.forename: A
authors.initials: A
authors.lastname: Vieillard-Baron
authors.forename: T
authors.initials: T
authors.lastname: Joseph
authors.forename: B
authors.initials: B
authors.lastname: Mesurolle
authors.forename: V L
authors.initials: VL
authors.lastname: Oliva
authors.forename: O
authors.initials: O
authors.lastname: Barré
authors.forename: F
authors.initials: F
authors.lastname: Bruckert
authors.forename: O
authors.initials: O
authors.lastname: Dubourg
authors.forename: P
authors.initials: P
authors.lastname: Lacombe
mesh_terms: D000792:Angiography; D004452:Echocardiography; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods