title: Step and shoot coronary CT angiography using 256-slice CT: effect of heart rate and heart rate variability on image quality.
abstract: OBJECTIVE
  To evaluate the effect of heart rate variability (HRV) and heart rate (HR) on intra-image "motion" and inter-image "stairstep" artefacts in step-and-shoot coronary CT angiography (CCTA) using a wide detector CT scanner.
  
  
  METHODS
  66 patients underwent step-and-shoot CCTA using 256-slice CT. Patients were divided into two groups (Group 1: HR <65 bpm, Group 2 ≥65bpm). Motion artefacts were quantified using a 5-point-scale. Stairstep artefacts were defined by measurements of misalignment. Image noise, contrast-to-noise-ratio (CNR), signal-to-noise-ratio (SNR), and radiation dose were assessed.
  
  
  RESULTS
  Mean HR was 66 ± 16.7 bpm (range: 45-125 bpm) and mean HRV was 10.7 ± 17.5 bpm. A significant correlation between HR and stairstep artefacts (r = 0.46, p < 0.001) and motion artefacts (r = 0.63, p < 0.001) was found. Group 2 showed significantly increased step artefacts with a mean misalignment of 1.4 mm compared to 0.4 mm in Group 1 (p < 0.001). There was no significant effect of HRV on stairstep artefacts (r = 0.15, p = 0.416) and motion artefacts (r = 0.13, p = 0.311). No significant differences in image noise, CNR, SNR, and radiation dose were seen.
  
  
  CONCLUSIONS
  Unlike CCTA using narrow CT detectors, HRV has no significant effect on motion and stairstep artefacts using a wide CT detector with high z-coverage. However, a higher HR still increases stairstep and motion artefacts.
authors.affiliation: Department of Radiology, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Strasse 22, 81675 Munich, Germany. muenzel@tum.de
authors.forename: D
authors.initials: D
authors.lastname: Muenzel
authors.forename: P B
authors.initials: PB
authors.lastname: Noel
authors.forename: F
authors.initials: F
authors.lastname: Dorn
authors.forename: M
authors.initials: M
authors.lastname: Dobritz
authors.forename: E J
authors.initials: EJ
authors.lastname: Rummeny
authors.forename: A
authors.initials: A
authors.lastname: Huber
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D017023:Coronary Angiography / Q000379:methods*; D003952:Diagnostic Imaging / Q000379:methods; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009038:Motion; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed / Q000379:methods*