title: Visualization of azygos arch valves using computed tomography: comparison of scanning delay times.
abstract: OBJECTIVE
  To evaluate the frequency and appearance of azygos arch valves after short and long scanning delays and high injection rates of contrast material (CM) using a 64-slice multi-detector-row computed tomography (MDCT).
  
  
  METHODS
  We retrospectively reviewed the findings from 264 contrast-enhanced MDCT chest examinations. The rate of injection for 300 mg I/ml CM was 3.0 ml/sec; the short and long scanning delays were 20 and 180 sec, respectively. The presence of residual CM in the azygos arch valves and reflux of CM into the azygos arch were recorded. A chi-square test was used to compare the frequency of residual CM in azygos arch valves and reflux of CM into the azygos arch in both groups.
  
  
  RESULTS
  Of the 132 examinations with short scanning delays, 91 (68.9%) demonstrated residual CM in azygos arch valves and 103 (78.0%) demonstrated reflux of CM into the azygos arch. A significantly higher frequency of reflux of CM into the azygos arch and residual CM in azygos arch valves was seen with short scanning delays than with long scanning delays (P<0.05). However, no reflux of CM into azygos arch was seen with long scanning delays.
  
  
  CONCLUSIONS
  Both reflux of CM into azygos arch valve and residual CM in the azygos arch were frequently seen using short scanning delays.
authors.affiliation: Department of Radiology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, Japan. jun@is.icc.u-tokai.ac.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Endo
authors.forename: Tamaki
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Jun
authors.initials: J
authors.lastname: Koizumi
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yamashita
authors.forename: Ayako
authors.initials: A
authors.lastname: Ro
authors.forename: Midori
authors.initials: M
authors.lastname: Saito
authors.forename: Yuri
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Kaoru
authors.initials: K
authors.lastname: Onoue
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Hashida
authors.forename: Shu
authors.initials: S
authors.lastname: Ikeda
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Imai
mesh_terms: D001401:Azygos Vein / Q000000981:diagnostic imaging*; D003287:Contrast Media; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media