title: Quantitative analysis of ECG-gated high-resolution contrast-enhanced MR angiography of the thoracic aorta.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effect of cardiac gating on the quality of images of the thoracic aorta at various levels during contrast-enhanced MR angiography compared with MR angiography without cardiac gating.
  
  
  METHODS
  Fifty patients underwent high-resolution contrast-enhanced MR angiography on a 1.5-T whole-body system. The 50 patients were composed of two groups of 25 consecutive patients; one group underwent MR angiography with ECG gating and the other group underwent MR angiography without ECG gating. A sagittal (3D) gradient-echo fast low-angle shot (FLASH) sequence (TR/TE, 2.8/1.4; flip angle, 25 degrees; readout, 512; voxel size, 1.4 x 0.8 x 1.3 mm) with an asymmetric k-space scanning scheme in all three gradient axes was used, and 0.2 mmol/kg of gadopentetate dimeglumine was injected at 2 mL/s. Sharpness of the thoracic aorta was evaluated at three levels by generating a signal intensity profile across the aortic vessel wall and calculating the distance between two points along a line representing the slope of the signal intensity profile. Both sides of the intensity profile were analyzed and averaged and then used to calculate sharpness. An additional group of six patients was included who had undergone both a gated and an ungated sequence; results of this group were analyzed independently.
  
  
  RESULTS
  Quantitative analysis of the sharpness of the ascending thoracic aorta showed a significant increase in sharpness in both the 50-patient and six-patient groups (p < 0.005) with the addition of cardiac gating.
  
  
  CONCLUSIONS
  Cardiac gating significantly improves the sharpness of the ascending aorta, a portion of the aorta that is subject to a great deal of blurring caused by cardiac motion. High-resolution contrast-enhanced MR angiography with cardiac gating can produce high quality images of the thoracic vasculature, thus enabling accurate diagnosis of vessel disease.
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, 676 N St. Clair St., Ste. 800, Chicago, IL 60611, USA.
authors.forename: Elliott M
authors.initials: EM
authors.lastname: Groves
authors.forename: William
authors.initials: W
authors.lastname: Bireley
authors.forename: Karin
authors.initials: K
authors.lastname: Dill
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Carroll
authors.forename: James C
authors.initials: JC
authors.lastname: Carr
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001013:Aorta, Thoracic / Q000473:pathology*; D001018:Aortic Diseases / Q000473:pathology*; D016477:Artifacts; D003287:Contrast Media; D004562:Electrocardiography / Q000379:methods; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009068:Movement; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA