title: Comparison of sequential and helical scanning for radiation dose and image quality: results of the Prospective Multicenter Study on Radiation Dose Estimates of Cardiac CT Angiography (PROTECTION) I Study.
abstract: OBJECTIVE
  Concerns have been raised about the radiation exposure of coronary CT angiography (CTA). Recently, a prospective ECG-triggered sequential coronary CTA technique was developed to reduce exposure to ionizing radiation. The purpose of this analysis was to determine the impact of a sequential scanning technique on image quality and radiation dose in a prespecified subgroup analysis of the Prospective Multicenter Study on Radiation Dose Estimates of Cardiac CT Angiography I (PROTECTION I) Study when compared with a standard helical scanning technique.
  
  
  METHODS
  This analysis comprises 685 64-MDCT coronary angiography studies of 47 international study sites in which the image quality was assessed by an experienced coronary CTA investigator using a 4-point score (1 = nondiagnostic, 4 = excellent image quality). Image quality was analyzed in all patients studied with the sequential scanning mode (n = 99) and in randomly selected patients of the population studied with the helical acquisition mode (n = 586). Radiation dose estimates were derived from the dose-length product (DLP) and a conversion coefficient for the chest (0.014 mSv x mGy(-1) x cm(-1)).
  
  
  RESULTS
  Although the sequential scanning mode significantly reduced radiation dose estimates by 68% from 11.2 mSv for the helical mode to 3.6 mSv for the sequential mode (p < 0.001), the median diagnostic image quality scores were comparable in both groups. The median diagnostic score for both scanning modes was 3.5 (interquartile range: sequential vs helical mode, 3.25-3.75 vs 3.0-3.75, respectively; p = 0.62).
  
  
  CONCLUSIONS
  The results of the PROTECTION I Study suggest that the prospective ECG-triggered sequential coronary CTA technique significantly reduces radiation dose without impairing image quality when compared with the standard retrospective helical data acquisition in patients with a low and stable heart rate.
authors.affiliation: Klinik für Herz und Kreislauferkrankungen, Deutsches Herzzentrum Munchen, Munich, Bavaria 80636, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Bischoff
authors.forename: Franziska
authors.initials: F
authors.lastname: Hein
authors.forename: Tanja
authors.initials: T
authors.lastname: Meyer
authors.forename: Markus
authors.initials: M
authors.lastname: Krebs
authors.forename: Martin
authors.initials: M
authors.lastname: Hadamitzky
authors.forename: Stefan
authors.initials: S
authors.lastname: Martinoff
authors.forename: Albert
authors.initials: A
authors.lastname: Schömig
authors.forename: Jörg
authors.initials: J
authors.lastname: Hausleiter
mesh_terms: D016009:Chi-Square Distribution; D017023:Coronary Angiography / Q000379:methods*; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D018709:Statistics, Nonparametric; D036542:Tomography, Spiral Computed; D014057:Tomography, X-Ray Computed / Q000379:methods*