title: Timing on 16-slice scanner and implications for 64-slice cardiac CT: do you start scanning immediately after breath hold?
abstract: OBJECTIVE
  Slow heart rate and small changes in heart rate are factors for improving image quality on spiral cardiac computed tomography (CT). The purpose of this study is to investigate whether it is possible to improve non-enhanced cardiac CT quality by delaying the data-acquisition window after breath hold.
  
  
  METHODS
  Electrocardiograph files (n = 240) for 16-slice non-enhanced cardiac CT scans were analyzed. Mean heart rates and maximal changes in heart rates between adjacent cardiac cycles were compared between phase 1 (defined as cardiac cycles 1-5), phase 2 (cardiac cycles 2-6), ... , and phase 6 (cardiac cycles 6-10).
  
  
  RESULTS
  Heart rates gradually increased by phases, but were limited to a range of 66.8-68.0 beats/min. Maximal changes in heart rates were 2.5 beats/min (phase 1) at the highest and 1.3 beats/min (phases 5 and 6) at the lowest (t-test; P < .01). Maximal changes in heart rates for more than five beats/min occurred in 24, eight, and eight patients on phases 1, 5, and 6, respectively (chi-square test; P < .01).
  
  
  CONCLUSIONS
  The delayed scan (four or five cardiac cycles after breath hold) has the potential to improve the quality of non-enhanced cardiac CT.
authors.affiliation: Department of Clinical Radiology, Hiroshima University Hospital, Minami-ku, Hiroshima 734-8551, Japan. horiguch@hiroshima-u.ac.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Horiguchi
authors.forename: Yun
authors.initials: Y
authors.lastname: Shen
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Hirai
authors.forename: Hideya
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Yuji
authors.initials: Y
authors.lastname: Akiyama
authors.forename: Minoru
authors.initials: M
authors.lastname: Ishifuro
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kakizawa
authors.forename: Masashi
authors.initials: M
authors.lastname: Hieda
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Tachikake
authors.forename: Noriaki
authors.initials: N
authors.lastname: Matsuura
authors.forename: Katsuhide
authors.initials: K
authors.lastname: Ito
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002114:Calcinosis / Q000000981:diagnostic imaging / Q000503:physiopathology; D003327:Coronary Disease / Q000000981:diagnostic imaging / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000000981:diagnostic imaging / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D012107:Research Design; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*