title: Assessing pulmonary perfusion in emphysema: automated quantification of perfused blood volume in dual-energy CTPA.
abstract: OBJECTIVE
  The objective of this study was to determine whether automated quantification of lung perfused blood volume (PBV) in dual-energy computed tomographic pulmonary angiography (DE-CTPA) can be used to assess the severity and regional distribution of pulmonary hypoperfusion in emphysema.
  
  
  METHODS
  We retrospectively analyzed 40 consecutive patients (mean age, 67 [13] years) with pulmonary emphysema, who have no cardiopulmonary comorbidities, and a DE-CTPA negative for pulmonary embolism. Automated quantification of global and regional pulmonary PBV was performed using the syngo Dual Energy application (Siemens Healthcare). Similarly, the global and regional degrees of parenchymal hypodensity were assessed automatically as the percentage of voxels with a computed tomographic density less than -900 Hounsfield unit. Emphysema severity was rated visually, and pulmonary function tests were obtained by chart review, if available.
  
  
  RESULTS
  Global PBV generated by automated quantification of pulmonary PBV in the DE-CTPA data sets showed a moderately strong but highly significant negative correlation with residual volume in percentage of the predicted residual volume (r = -0.62; P = 0.002; n = 23) and a positive correlation with forced expiratory volume in 1 second in percentage of the predicted forced expiratory volume in 1 second (r = 0.67; P < 0.001; n = 23). Global PBV values strongly correlated with diffusing lung capacity for carbon monoxide (r = 0.80; P < 0.001; n = 15). Pulmonary PBV values decreased with visual emphysema severity (r = -0.46, P = 0.003, n = 40). Moderate negative correlations were found between global PBV values and parenchymal hypodensity both in a per-patient (r = -0.63; P < 0.001; n = 40) and per-region analyses (r = -0.62; P < 0.001; n = 40).
  
  
  CONCLUSIONS
  Dual-energy computed tomographic pulmonary angiography allows simultaneous assessment of lung morphology, parenchymal density, and pulmonary PBV. In patients with pulmonary emphysema, automated quantification of pulmonary PBV in DE-CTPA can be used for a quick, reader-independent estimation of global and regional pulmonary perfusion, which correlates with several lung function parameters.
authors.affiliation: Department of Clinical Radiology, Ludwig Maximilians-University, Munich, Germany. felix.meinel@med.uni-muenchen.de
authors.forename: Felix G
authors.initials: FG
authors.lastname: Meinel
authors.forename: Anita
authors.initials: A
authors.lastname: Graef
authors.forename: Sven F
authors.initials: SF
authors.lastname: Thieme
authors.forename: Fabian
authors.initials: F
authors.lastname: Bamberg
authors.forename: Florian
authors.initials: F
authors.lastname: Schwarz
authors.forename: Wieland H
authors.initials: WH
authors.lastname: Sommer
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Helck
authors.forename: Claus
authors.initials: C
authors.lastname: Neurohr
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Thorsten R C
authors.initials: TR
authors.lastname: Johnson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography / Q000379:methods; D001810:Blood Volume; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed