title: Coronary computed tomography angiography using prospective electrocardiography-gated axial scans with 64-detector computed tomography: evaluation of stair-step artifacts and padding time.
abstract: OBJECTIVE
  We compared stair-step artifacts and radiation dose between prospective electrocardiography (ECG)-gated coronary computed tomography angiography (prospective CCTA) and retrospective CCTA using 64-detector CT and determined the optimal padding time (PT) for prospective CCTA.
  
  
  METHODS
  We retrospectively evaluated 183 patients [mean heart rate (HR) <65 beats/min, maximum HR instability <5 beats/min] who had undergone CCTA. We scored stair-step artifacts from 1 (severe) to 5 (none) and evaluated the effective dose in 53 patients with retrospective CCTA and 130 with prospective CCTA (PT 200 ms, n = 32; PT 50 ms, n = 98).
  
  
  RESULTS
  Mean artifact scores were 4.3 in both retrospective and prospective CCTAs. However, statistically more arteries scored <3 (nonassessable) on prospective CCTA (P < 0.001). Mean scores for prospective CCTA with 200- and 50-ms PT were 4.1 and 4.3, respectively (no significant difference). The radiation dose of prospective CCTA was reduced by 59.1% to 80.7%.
  
  
  CONCLUSIONS
  Prospective CCTA reduces the radiation dose and allows diagnostic imaging in most cases but shows more nonevaluable artifacts than retrospective CCTA. Use of 50-ms instead of 200-ms PT appears to maintain image quality in patients with a mean HR < 65 beats/min and HR instability of <5 beats/min.
authors.affiliation: Department of Diagnostic Radiology, Saitama Medical University International Medical Center, 1397-1 Yamane, Hidaka, 350-1298, Japan. fkimura@saitama-med.ac.jp
authors.forename: Fumiko
authors.initials: F
authors.lastname: Kimura
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Umezawa
authors.forename: Tomonari
authors.initials: T
authors.lastname: Asano
authors.forename: Ruri
authors.initials: R
authors.lastname: Chihara
authors.forename: Naoko
authors.initials: N
authors.lastname: Nishi
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Nishimura
authors.forename: Fumikazu
authors.initials: F
authors.lastname: Sakai
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000175:diagnosis; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007472:Iohexol; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult
chemical_list: D003287:Contrast Media; D007472:Iohexol