title: Narrowing the phase window width in prospectively ECG-gated single heart beat 320-detector row coronary CT angiography.
abstract: OBJECTIVE
  To evaluate the relationship between the phase window width and image quality in prospectively ECG-gated 320-detector row coronary CTA, and to evaluate the relationship between heart rate and the number of cardiac phases with diagnostic quality images.
  
  
  METHODS
  Thirty-six phases (60-95% R-R, 1% increments) were reconstructed in 41 consecutive prospectively gated single R-R 320 x 0.5 mm detector row coronary CTA patients. For each phase, two cardiovascular imagers retrospectively documented the phases considered diagnostic for the left anterior descending (LAD), left circumflex (LCx), and right coronary artery (RCA). The smallest phase window width including at least one diagnostic phase for 95% of coronary arteries was determined, and after accounting for sampling variation, the same smallest window width was estimated for the general population. Inter-rater agreement was determined. A linear regression model evaluated the relationship between heart rate and width of diagnostic phase windows.
  
  
  RESULTS
  Widening the phase window width increases the proportion of coronary arteries with at least one diagnostic phase. Among the 41 patients, 95% of vessels had a diagnostic phase in the 72-77% phase window. Accounting for sampling variation, the 72-81% phase window has a 0.95 probability of including a diagnostic phase for 95% of coronary arteries in the general population. Interobserver agreement was 0.959 with 0.95 confidence interval [0.908, 0.987]. Patients with a lower heart rate had significantly more diagnostic phases.
  
  
  CONCLUSIONS
  For prospectively ECG-gated single heart beat coronary CTA, a phase window width of 10% will reduce patient radiation and yield diagnostic images in >90% of patients. Heart rate control is an important component of 320-detector row prospectively gated CT dose reduction.
authors.affiliation: Noninvasive Cardiovascular Imaging, Brigham and Women's Hospital, Boston, MA 02115, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Steigner
authors.forename: Hansel J
authors.initials: HJ
authors.lastname: Otero
authors.forename: Tianxi
authors.initials: T
authors.lastname: Cai
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Mitsouras
authors.forename: Leelakrishna
authors.initials: L
authors.lastname: Nallamshetty
authors.forename: Amanda G
authors.initials: AG
authors.lastname: Whitmore
authors.forename: Hale
authors.initials: H
authors.lastname: Ersoy
authors.forename: Noah A
authors.initials: NA
authors.lastname: Levit
authors.forename: Marcelo F
authors.initials: MF
authors.lastname: Di Carli
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Rybicki
mesh_terms: D000328:Adult; D000368:Aged; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods*; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007479:Iopamidol; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D007479:Iopamidol