title: Advanced virtual monoenergetic images: improving the contrast of dual-energy CT pulmonary angiography.
abstract: OBJECTIVE
  To investigate the value of advanced virtual monoenergetic image reconstruction (mono-plus) from dual-energy computed tomography (CT) for improving the contrast of CT pulmonary angiography (CTPA).
  
  
  METHODS
  Forty consecutive patients (25 women, mean 62.5 years, range 28-87 years) underwent 192-section dual-source CTPA with dual-energy CT (90/150 SnkVp) after the administration of 60 ml contrast media (300 mg iodine/ml). Conventional virtual monochromatic images at 60 keV and 17 mono-plus image datasets from 40-190 keV (in 10 keV steps) were reconstructed. Subjective image quality (artefacts, subjective noise) was rated. Attenuation was measured in the pulmonary trunk and in the right lower lobe pulmonary artery; noise was measured in the periscapular musculature. The signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated for each patient and dataset. Comparisons between monochromatic images and mono-plus images were performed by repeated measures analysis of variance (ANOVA) with post-hoc Bonferroni correction.
  
  
  RESULTS
  Interreader agreement was good to excellent for subjective image quality (ICC: 0.616-0.889). As compared to conventional 60 keV images, artefacts occurred less (p=0.001) and subjective noise was rated lower (p<0.001) in mono-plus 40 keV images. Noise was lower (p<0.001), and the SNR and CNR in the pulmonary trunk and right lower lobe pulmonary artery were higher (both, p<0.001) in mono-plus 40 keV images compared to conventional monoenergetic 60 keV images. Transient interruption of contrast (TIC) was found in 14/40 (35%) of patients, with subjective contrast being similar 8/40 (20%) or higher 32/40 (80%) in mono-plus 40 keV as compared to conventional monoenergetic 60 keV images.
  
  
  CONCLUSIONS
  Compared to conventional virtual monoenergetic imaging, mono-plus images at 40 keV improve the contrast of dual-energy CTPA.
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Meier
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Wurnig
authors.affiliation: Division of Radiology and Nuclear Medicine, Kantonsspital St Gallen, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Desbiolles
authors.affiliation: Division of Radiology and Nuclear Medicine, Kantonsspital St Gallen, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Leschka
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Frauenfelder
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland. Electronic address: hatem.alkadhi@usz.c.
authors.forename: H
authors.initials: H
authors.lastname: Alkadhi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D016477:Artifacts; D003287:Contrast Media; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods / Q000592:standards*; D007455:Iodine; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods / Q000592:standards; D012189:Retrospective Studies; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards
chemical_list: D003287:Contrast Media; D007455:Iodine