title: Retrospectively ECG-gated multi-detector row CT of the chest: does ECG-gating improve three-dimensional visualization of the bronchial tree?
abstract: OBJECTIVE
  To determine the impact of retrospectively ECG-gated multi-detector row CT (MDCT) on three-dimensional (3D) visualization of the bronchial tree and virtual bronchoscopy (VB) as compared to non-ECG-gated data acquisition.
  
  
  METHODS
  Contrast-enhanced retrospectively ECG-gated and non-ECG-gated MDCT of the chest was performed in 25 consecutive patients referred for assessment of coronary artery bypass grafts and pathology of the ascending aorta. ECG-gated MDCT data were reconstructed in diastole using an absolute reverse delay of - 400 msec in all patients. In 10 patients additional reconstructions at - 200 msec, - 300 msec, and - 500 msec prior to the R-wave were performed. Shaded surface display (SSD) and virtual bronchoscopy (VB) for visualization of the bronchial segments was performed with ECG-gated and non-ECG-gated MDCT data. The visualization of the bronchial tree underwent blinded scoring. Effective radiation dose and signal-to-noise ratio (SNR) for both techniques were compared.
  
  
  RESULTS
  There was no significant difference in visualizing single bronchial segments using ECG-gated compared to non-ECG-gated MDCT data. However, the total sum of scores for all bronchial segments visualized with non-ECG-gated MDCT was significantly higher compared to ECG-gated MDCT (P < 0.05). The summary scores for visualization of bronchial segments for different diastolic reconstructions did not differ significantly. The effective radiation dose and the SNR were significantly higher with the ECG-gated acquisition technique (P < 0.05).
  
  
  CONCLUSIONS
  The bronchial tree is significantly better visualized when using non-ECG-gated MDCT compared to ECG-gated MDCT. Additionally, non-ECG-gated techniques require less radiation exposure. Thus, the current retrospective ECG-gating technique does not provide any additional benefit for 3D visualization of the bronchial tree and VB.
authors.affiliation: Department Medical Radiology, Institute of Diagnostic Radiology, University Hospital Zurich, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Schertler
authors.forename: S
authors.initials: S
authors.lastname: Wildermuth
authors.forename: J K
authors.initials: JK
authors.lastname: Willmann
authors.forename: D W
authors.initials: DW
authors.lastname: Crook
authors.forename: B
authors.initials: B
authors.lastname: Marincek
authors.forename: T
authors.initials: T
authors.lastname: Boehm
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000784:Aortic Dissection / Q000000981:diagnostic imaging; D001014:Aortic Aneurysm / Q000000981:diagnostic imaging; D001980:Bronchi; D001999:Bronchoscopy / Q000379:methods*; D001026:Coronary Artery Bypass; D003627:Data Interpretation, Statistical; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D013902:Radiography, Thoracic; D014057:Tomography, X-Ray Computed / Q000379:methods*