title: Whole-chest 64-MDCT of emergency department patients with nonspecific chest pain: Radiation dose and coronary artery image quality with prospective ECG triggering versus retrospective ECG gating.
abstract: OBJECTIVE
  The purpose of this study was to compare the patient radiation dose and coronary artery image quality of long-z-axis whole-chest 64-MDCT performed with retrospective ECG gating with those of CT performed with prospective ECG triggering in the evaluation of emergency department patients with nonspecific chest pain.
  
  
  METHODS
  Consecutively registered emergency department patients with nonspecific low-to-moderate-risk chest pain underwent whole-chest CT with retrospective gating (n = 41) or prospective triggering (n = 31). Effective patient radiation doses were estimated and compared by use of unpaired Student's t tests. Two reviewers independently scored the quality of images of the coronary arteries, and the scores were compared by use of ordinal logistic regression.
  
  
  RESULTS
  Age, heart rate, body mass index, and z-axis coverage were not statistically different between the two groups. For retrospective gating, the mean effective radiation dose was 31.8 +/- 5.1 mSv; for prospective triggering, the mean effective radiation dose was 9.2 +/- 2.2 mSv (prospective triggering 71% lower, p < 0.001). Two of 512 segments imaged with retrospective gating were nonevaluable (0.4%), and two of 394 segments imaged with prospective triggering were nonevaluable (0.5%). Prospectively triggered images were 2.2 (95% CI, 1.1-4.5) times as likely as retrospectively gated images to receive a high image quality score for each segment after adjustment for segment differences (p < 0.05).
  
  
  CONCLUSIONS
  For long-z-axis whole-chest 64-MDCT of emergency department patients with nonspecific chest pain, use of prospective ECG triggering may result in substantially lower patient radiation doses and better coronary artery image quality than is achieved with retrospective ECG gating.
authors.affiliation: Department of Radiology, University of Washington School of Medicine, Seattle, 98195, USA. wshuman@u.washington.edu
authors.forename: William P
authors.initials: WP
authors.lastname: Shuman
authors.forename: Kelley R
authors.initials: KR
authors.lastname: Branch
authors.forename: Janet M
authors.initials: JM
authors.lastname: May
authors.forename: Lee M
authors.initials: LM
authors.lastname: Mitsumori
authors.forename: Jared N
authors.initials: JN
authors.lastname: Strote
authors.forename: Bill H
authors.initials: BH
authors.lastname: Warren
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Dubinsky
authors.forename: David W
authors.initials: DW
authors.lastname: Lockhart
authors.forename: James H
authors.initials: JH
authors.lastname: Caldwell
mesh_terms: D001822:Body Burden; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D002637:Chest Pain / Q000000981:diagnostic imaging*; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D013902:Radiography, Thoracic / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*