title: Image quality and radiation exposure with prospectively ECG-triggered axial scanning for coronary CT angiography: the multicenter, multivendor, randomized PROTECTION-III study.
abstract: OBJECTIVE
  The purpose of this study was to evaluate image quality and radiation dose using a prospectively electrocardiogram (ECG)-triggered axial scan protocol compared with standard retrospective ECG-gated helical scanning for coronary computed tomography angiography.
  
  
  BACKGROUND
  Concerns have been raised regarding radiation exposure during coronary computed tomography angiography. Although the use of prospectively ECG-triggered axial scan protocols may effectively lower radiation dose compared with helical scanning, it is unknown whether image quality is maintained in a clinical setting.
  
  
  METHODS
  In a prospective, multicenter, multivendor trial, 400 patients with low and stable heart rates were randomized to either an axial or a helical coronary computed tomography angiography scan protocol. The primary endpoint was to demonstrate noninferiority in image quality with the axial scan protocol, which was assessed on a 4-point scale (1 = nondiagnostic, 4 = excellent image quality). Secondary endpoints included radiation dose and the rate of downstream testing during 30-day follow-up.
  
  
  RESULTS
  Image quality in patients scanned with the axial scan protocol (score 3.36 ± 0.59) was not inferior compared with helical scan protocols (3.37 ± 0.59) (p for noninferiority <0.004). Axial scanning was associated with a 69% reduction in radiation exposure (dose-length product [estimated effective dose] 252 ± 147 mGy · cm [3.5 ± 2.1 mSv] vs. 802 ± 419 mGy · cm [11.2 ± 5.9 mSv] for axial vs. helical scan protocols, p < 0.001). The rate of downstream testing did not differ (13.8% vs. 15.9% for axial vs. helical scan protocols, p = 0.555).
  
  
  CONCLUSIONS
  In patients with stable and low heart rates, the prospectively ECG-triggered axial scan protocol maintained image quality but reduced radiation exposure by 69% compared with helical scanning. Axial computed tomography data acquisition should be strongly recommended in suitable patients to avoid unnecessarily high radiation exposure.
authors.affiliation: Klinik für Herz- und Kreislauferkrankungen, Deutsches Herzzentrum München, Klinik an der Technischen Universität München, Munich, Germany. hausleiter@dhm.mhn.de
authors.forename: Jörg
authors.initials: J
authors.lastname: Hausleiter
authors.forename: Tanja S
authors.initials: TS
authors.lastname: Meyer
authors.forename: Eugenio
authors.initials: E
authors.lastname: Martuscelli
authors.forename: Pietro
authors.initials: P
authors.lastname: Spagnolo
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Patricia
authors.initials: P
authors.lastname: Carrascosa
authors.forename: Thomas
authors.initials: T
authors.lastname: Anger
authors.forename: Lukas
authors.initials: L
authors.lastname: Lehmkuhl
authors.forename: Hatem
authors.initials: H
authors.lastname: Alkadhi
authors.forename: Stefan
authors.initials: S
authors.lastname: Martinoff
authors.forename: Martin
authors.initials: M
authors.lastname: Hadamitzky
authors.forename: Franziska
authors.initials: F
authors.lastname: Hein
authors.forename: Bernhard
authors.initials: B
authors.lastname: Bischoff
authors.forename: Miriam
authors.initials: M
authors.lastname: Kuse
authors.forename: Albert
authors.initials: A
authors.lastname: Schömig
authors.forename: Stephan
authors.initials: S
authors.lastname: Achenbach
mesh_terms: D001118:Argentina; D015992:Body Mass Index; D055424:Cardiac-Gated Imaging Techniques; D016009:Chi-Square Distribution; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004562:Electrocardiography; D005060:Europe; D006339:Heart Rate; D006801:Humans; D007564:Japan; D011237:Predictive Value of Tests; D011379:Prognosis; D011829:Radiation Dosage; D013997:Time Factors; D036542:Tomography, Spiral Computed