title: Imaging of acute pulmonary embolism using a dual energy CT system with rapid kVp switching: initial results.
abstract: OBJECTIVE
  Computed tomography pulmonary angiography (CTPA) is considered as clinical gold standard for diagnosing pulmonary embolism (PE). Whereas conventional CTPA only offers anatomic information, dual energy CT (DECT) provides functional information on blood volume as surrogate of perfusion by assessing the pulmonary iodine distribution. The purpose of this study was to evaluate the feasibility of lung perfusion imaging using a single-tube DECT scanner with rapid kVp switching.
  
  
  METHODS
  Fourteen patients with suspicion of acute PE underwent DECT. Two experienced radiologists assessed the CTPA images and lung perfusion maps regarding the presence of PE. The image quality was rated using a semi-quantitative 5-point scale: 1 (=excellent) to 5 (=non-diagnostic). Iodine concentrations were quantified by a ROI analysis.
  
  
  RESULTS
  Seventy perfusion defects were identified in 266 lung segments: 13 (19%) were rated as consistent with PE. Five patients had signs of PE at CTPA. All patients with occlusive clots were correctly identified by DECT perfusion maps. On a per patient basis the sensitivity and specificity were 80.0% and 88.9%, respectively, while on a per segment basis it was 40.0% and 97.6%, respectively. None of the patients with a homogeneous perfusion map had an abnormal CTPA. The overall image quality of the perfusion maps was rated with a mean score of 2.6 ± 0.6. There was a significant ventrodorsal gradient of the median iodine concentrations (1.1mg/cm(3) vs. 1.7 mg/cm(3)).
  
  
  CONCLUSIONS
  Lung perfusion imaging on a DE CT-system with fast kVp-switching is feasible. DECT might be a helpful adjunct to assess the clinical severity of PE.
authors.affiliation: Department of Clinical Radiology, Medical Center of the University of Munich, Nussbaumstraße 20, 80336 Munich, Germany. Lucas.Geyer@med.uni-muenchen.de
authors.forename: Lucas L
authors.initials: LL
authors.lastname: Geyer
authors.forename: Michael
authors.initials: M
authors.lastname: Scherr
authors.forename: Markus
authors.initials: M
authors.lastname: Körner
authors.forename: Stefan
authors.initials: S
authors.lastname: Wirth
authors.forename: Paul
authors.initials: P
authors.lastname: Deak
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Ulrich
authors.initials: U
authors.lastname: Linsenmaier
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000465:Algorithms; D000792:Angiography / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*