title: Dual-energy CT for assessment of the severity of acute pulmonary embolism: pulmonary perfusion defect score compared with CT angiographic obstruction score and right ventricular/left ventricular diameter ratio.
abstract: OBJECTIVE
  The purpose of this study was to prospectively evaluate the usefulness of scoring perfusion defects on perfusion images at dual-energy CT for assessment of the severity of pulmonary embolism.
  
  
  METHODS
  Thirty patients (13 men, 17 women; mean age, 55 +/- 15 [SD] years; range, 26-81 years) with pulmonary thromboembolism underwent dual-source CT at two voltages (140 and 80 kV). The weighted average image of two acquisitions was used for CT angiograms, and a color-coded iodine image was used for perfusion images. Two thoracic radiologists with 15 and 6 years of clinical experience independently assigned perfusion defect scores to perfusion images and both a CT angiographic (CTA) obstruction score and right ventricular-to-left ventricular (RV/LV) diameter ratio to CT angiograms. The CTA obstruction score was based on the Qanadli method. The perfusion defect score was defined as Sigma (n . d) / 40 x 100, where n is the number of segments and d is the degree of perfusion from 0 to 2. Correlations between perfusion defect score, CTA obstruction score, and RV/LV diameter ratio were evaluated. Agreement between perfusion defect score and CTA score was assessed per patient and per segment. Interobserver agreement regarding perfusion defect and CTA obstruction scores was analyzed.
  
  
  RESULTS
  Perfusion defect and CTA obstruction scores had good correlation with RV/LV diameter ratio (r = 0.69, r = 0.66; all p < 0.001). Per patient, correlation between perfusion defect score and CTA obstruction score also was good (reader 1, r = 0.87; reader 2, r = 0.85; all p < 0.001). Per segment, moderate agreement was found between perfusion defect score and CTA obstruction score (reader 1, kappa = 0.56; reader 2, kappa = 0.51; all p < 0.05). Both readers were in strong agreement on perfusion defect score and CTA obstruction score.
  
  
  CONCLUSIONS
  The proposed perfusion defect score had good correlation with RV/LV diameter ratio and CTA obstruction score. Therefore, acquisition of perfusion images at dual-energy CT may be helpful for assessing the severity of acute pulmonary embolism.
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 388-1, Pungnap-dong, Songpa-gu, Seoul 138-736, Republic of Korea.
authors.forename: Eun Jin
authors.initials: EJ
authors.lastname: Chae
authors.forename: Joon Beom
authors.initials: JB
authors.lastname: Seo
authors.forename: Yu Mi
authors.initials: YM
authors.lastname: Jang
authors.forename: Bernhard
authors.initials: B
authors.lastname: Krauss
authors.forename: Choong Wook
authors.initials: CW
authors.lastname: Lee
authors.forename: Hyun Joo
authors.initials: HJ
authors.lastname: Lee
authors.forename: Koun-Sik
authors.initials: KS
authors.lastname: Song
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography / Q000379:methods*; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011652:Pulmonary Circulation; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011857:Radiographic Image Interpretation, Computer-Assisted; D012720:Severity of Illness Index; D012984:Software; D036542:Tomography, Spiral Computed / Q000379:methods*