title: Dose modulated retrospective ECG-gated versus non-gated 64-row CT angiography of the aorta at the same radiation dose: comparison of motion artifacts, diagnostic confidence and signal-to-noise-ratios.
abstract: OBJECTIVE
  To compare ECG-gated and non-gated CT angiography of the aorta at the same radiation dose, with regard to motion artifacts (MA), diagnostic confidence (DC) and signal-to-noise-ratios (SNRs).
  
  
  METHODS
  Sixty consecutive patients prospectively randomized into two groups underwent 64-row CT angiography, with or without dose-modulated ECG-gating, of the entire aorta, due to several pathologies of the ascending aorta. MA and DC were both assessed using a four-point scale. SNRs were calculated by dividing the mean enhancement by the standard deviation. The dose-length-product (DLP) of each examination was recorded and the effective dose was estimated.
  
  
  RESULTS
  Dose-modulated ECG-gating showed statistically significant advantages over non-gated CT angiography, with regard to MA (p<0.001) and DC (p<0.001), at the aortic valve, at the origin of the coronary arteries, and at the dissection membrane, with a significant correlation (p<0.001) between MA and DC. At the aortic wall, however, ECG-gated CT angiography showed statistically significant fewer MA (p<0.001), but not a statistically significant higher DC (p=0.137) compared to non-gated CT angiography. At the supra-aortic vessels and the descending aorta, the ECG-triggering showed no statistically significant differences with regard to MA (p=0.861 and 0.526, respectively) and DC (p=1.88 and 0.728, respectively). The effective dose of ECG-gated CT angiography (23.24mSv; range, 18.43-25.94mSv) did not differ significantly (p=0.051) from that of non-gated CT angiography (24.28mSv; range, 19.37-29.27mSv).
  
  
  CONCLUSIONS
  ECG-gated CT angiography of the entire aorta reduces MA and results in a higher DC with the same SNR, compared to non-gated CT angiography at the same radiation dose.
authors.affiliation: Department of Radiology, Medical University of Vienna, Vienna, Austria.
authors.forename: Ruediger E
authors.initials: RE
authors.lastname: Schernthaner
authors.forename: Alfred
authors.initials: A
authors.lastname: Stadler
authors.forename: Dietrich
authors.initials: D
authors.lastname: Beitzke
authors.forename: Peter
authors.initials: P
authors.lastname: Homolka
authors.forename: Michael
authors.initials: M
authors.lastname: Weber
authors.forename: Johannes
authors.initials: J
authors.lastname: Lammer
authors.forename: Martin
authors.initials: M
authors.lastname: Czerny
authors.forename: Christian
authors.initials: C
authors.lastname: Loewe
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000792:Angiography / Q000379:methods*; D001027:Aortography / Q000379:methods*; D016477:Artifacts; D001822:Body Burden; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D009068:Movement; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*