title: ECG-gated reconstructed multi-detector row CT coronary angiography: effect of varying trigger delay on image quality.
abstract: OBJECTIVE
  To evaluate the effectiveness of electrocardiographically (ECG)-gated retrospective image reconstruction for multi-detector row computed tomographic (CT) coronary angiography in reducing cardiac motion artifacts and to evaluate the influence of heart rate on cardiac image quality.
  
  
  METHODS
  Sixty-five patients with different heart rates underwent coronary CT angiography. Raw helical CT data and ECG tracings were combined to retrospectively reconstruct at the defined consecutive z position with a temporal resolution of 250 msec per section. The starting points of the reconstruction were chosen between 30% and 80% of the R-R intervals. The relationships between heart rate, trigger delay, and image quality were analyzed.
  
  
  RESULTS
  Optimal image quality was achieved with a 50% trigger delay for the right coronary artery and 60% for the left circumflex coronary artery. Optimal image quality for the left anterior descending coronary artery was equally obtained at 50% and 60% triggering. A significant negative correlation was observed between heart rate and image quality (P <.05). The best image quality was achieved when the heart rate was less than 74.5 beats per minute.
  
  
  CONCLUSIONS
  To achieve high image quality, the heart rate should be sufficiently slow. Selection of appropriate trigger delays and a decreasing heart rate are effective to reduce cardiac motion artifacts.
authors.affiliation: Institute of Clinical Radiology, Klinikum Grosshadern, University of Munich, Marchioninistrasse 15, 81377 Munich, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Hong
authors.forename: C R
authors.initials: CR
authors.lastname: Becker
authors.forename: A
authors.initials: A
authors.lastname: Huber
authors.forename: U J
authors.initials: UJ
authors.lastname: Schoepf
authors.forename: B
authors.initials: B
authors.lastname: Ohnesorge
authors.forename: A
authors.initials: A
authors.lastname: Knez
authors.forename: R
authors.initials: R
authors.lastname: Brüning
authors.forename: M F
authors.initials: MF
authors.lastname: Reiser
mesh_terms: D000328:Adult; D000368:Aged; D017023:Coronary Angiography; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed