title: Spectral optimization of chest CT angiography with reduced iodine load: experience in 80 patients evaluated with dual-source, dual-energy CT.
abstract: OBJECTIVE
  To determine the energy levels that provide optimal imaging of thoracic circulation at dual-energy computed tomographic (CT) angiography with reduced iodine load in comparison with a standard technique.
  
  
  METHODS
  The institutional review board approved the study with waiver of patient consent. Eighty patients underwent a dual-source, dual-energy CT examination after administration of low-concentration contrast material (170 mg of iodine per milliliter), and eight series of images were reconstructed, including the original polychromatic images at 80 and 140 kV and six series of virtual monochromatic spectral images at 50, 60, 70, 80, 90, and 100 keV. For each vascular compartment, the energy level that provided optimal evaluation on virtual monochromatic spectral images was determined, and these series were compared with the polychromatic dual-energy images and with standard chest CT images that were used as controls. Comparisons between groups were performed by using the paired Student t test for continuous variables and the McNemar test for categorical variables. Comparisons between dual-energy and standard CT images were performed by using the unpaired Student t test for continuous variables and the χ(2) test for categorical variables.
  
  
  RESULTS
  For the aorta, pulmonary arteries, and veins, the reconstruction at 60 keV provided adequate attenuation without marked beam-hardening artifacts in 90% of patients, with the highest contrast-to-noise and signal-to-noise ratios, the lowest level of subjective noise, and no significant differences with images at 80 kV (mean energy, 54 keV). For the superior vena cava and brachiocephalic veins, the reconstructions at 100 keV enabled artifact-free analysis of the perivascular anatomic zone without a significant difference with images at 140 kV (mean energy, 92 keV). Compared with standard CT images acquired after administration of a 35% iodinated contrast agent, there was a statistically significant reduction in the frequency of artifacts around systemic veins at 100 keV (P < .001) and similar overall image quality for central vessels at 60 keV (P > .05).
  
  
  CONCLUSIONS
  An optimal analysis of thoracic circulation can be achieved on virtual monochromatic spectral images at 60 keV and 100 keV and on the original polychromatic images at 80 kV and 140 kV.
  
  
  BACKGROUND
  http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120195/-/DC1.
authors: Department of Thoracic Imaging, Hôpital Calmette (EA 2694 Université Lille Nord de France, Boulevard Jules Leclercq, 59037 Lille, France.
authors: Marie-Aurélie
authors: MA
authors: Delesalle
authors: François
authors: F
authors: Pontana
authors: Alain
authors: A
authors: Duhamel
authors: Jean-Baptiste
authors: JB
authors: Faivre
authors: Thomas
authors: T
authors: Flohr
authors: Nunzia
authors: N
authors: Tacelli
authors: Jacques
authors: J
authors: Remy
authors: Martine
authors: M
authors: Remy-Jardin
mesh_terms: D000792:Angiography / Q000379:methods*; D016009:Chi-Square Distribution; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007472:Iohexol / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D013902:Radiography, Thoracic / Q000379:methods*; D013899:Thoracic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol