title: Improving Image Quality of Bronchial Arteries with Virtual Monochromatic Spectral CT Images.
abstract: OBJECTIVE
  To evaluate the clinical value of using monochromatic images in spectral CT pulmonary angiography to improve image quality of bronchial arteries.
  
  
  METHODS
  We retrospectively analyzed the chest CT images of 38 patients who underwent contrast-enhanced spectral CT. These images included a set of 140kVp polychromatic images and the default 70keV monochromatic images. Using the standard Gemstone Spectral Imaging (GSI) viewer on an advanced workstation (AW4.6,GE Healthcare), an optimal energy level (in keV) for obtaining the best contrast-to-noise ratio (CNR) for the artery could be automatically obtained. The signal-to-noise ratio (SNR), CNR and objective image quality score (1-5) for these 3 image sets (140kVp, 70keV and optimal energy level) were obtained and, statistically compared. The image quality score consistency between the two observers was also evaluated using Kappa test.
  
  
  RESULTS
  The optimal energy levels for obtaining the best CNR were 62.58±2.74keV.SNR and CNR from the 140kVp polychromatic, 70keV and optimal keV monochromatic images were (16.44±5.85, 13.24±5.52), (20.79±7.45, 16.69±6.27) and (24.9±9.91, 20.53±8.46), respectively. The corresponding subjective image quality scores were 1.97±0.82, 3.24±0.75, and 4.47±0.60. SNR, CNR and subjective scores had significant difference among groups (all p<0.001). The optimal keV monochromatic images were superior to the 70keV monochromatic and 140kVp polychromatic images, and there was high agreement between the two observers on image quality score (kappa>0.80).
  
  
  CONCLUSIONS
  Virtual monochromatic images at approximately 63keV in dual-energy spectral CT pulmonary angiography yielded the best CNR and highest diagnostic confidence for imaging bronchial arteries.
authors.affiliation: Affiliated Hospital of Shannxi University of Traditional Chinese Medicine Radiology Dept, Xianyang City, Shaanxi, China.
authors.forename: Guangming
authors.initials: G
authors.lastname: Ma
authors.affiliation: Affiliated Hospital of Shannxi University of Traditional Chinese Medicine Radiology Dept, Xianyang City, Shaanxi, China.
authors.forename: Taiping
authors.initials: T
authors.lastname: He
authors.affiliation: Affiliated Hospital of Shannxi University of Traditional Chinese Medicine Radiology Dept, Xianyang City, Shaanxi, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Affiliated Hospital of Shannxi University of Traditional Chinese Medicine Radiology Dept, Xianyang City, Shaanxi, China.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Duan
authors.affiliation: Affiliated Hospital of Shannxi University of Traditional Chinese Medicine Radiology Dept, Xianyang City, Shaanxi, China.
authors.forename: Chuangbo
authors.initials: C
authors.lastname: Yang
mesh_terms: D000792:Angiography; D001981:Bronchial Arteries / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed