title: Improved venous suppression on renal MR angiography with recessed elliptical centric ordering of K-space.
abstract: OBJECTIVE
  To evaluate recessed elliptical centric ordering of k-space in renal magnetic resonance (MR) angiography.
  
  
  METHODS
  All imaging was performed on the same 1.5 T MR imaging system (GE Signa CVi) using the body coil for signal transmission and a phased array coil for reception. Gd, 30 ml, was injected manually at 2 ml/sec timed with automatic triggering (SmartPrep). In thirty patients using standard elliptical centric ordering, the scanner paused 8 seconds between detection of the leading edge of the Gd bolus and initiation of scanning beginning with the center of k-space. For the recessed-elliptical centric ordering in 20 consecutive patients, this delay was reduced to 4 seconds but the absolute center of k-space recessed in by 4 seconds such that in all patients the absolute center of k-space was acquired 8 seconds after detecting the leading edge of the bolus. On the arterial phase images signal-to-noise ratio (SNR) was measured in the aorta, each renal artery and vein and contrast-to-noise ratio (CNR) was measured relative to subcutaneous fat. The standard deviation of signal outside the patient was considered to be "noise" for calculation of SNR and CNR. Incidence of ringing artifact in the aorta and renal veins was noted.
  
  
  RESULTS
  Aorta SNR and CNR was significantly higher with the recessed technique (p = 0.02) and the ratio of renal artery signal to renal vein signal was higher with the recessed technique, 4 ± 2, compared to standard elliptical centric, 3 ± 2 (p = 0.03). Ringing artifact was also reduced with the recessed technique in both the aorta and renal veins.
  
  
  CONCLUSIONS
  Gadolinium-enhanced renal MR angiography is improved by recessing the absolute center of k-space.
authors.affiliation: Department of Radiology, Weill Medical College of Cornell University, New York, NY 10021, USA.
authors.forename: Bernard
authors.initials: B
authors.lastname: Ho
authors.forename: Minh
authors.initials: M
authors.lastname: Chao
authors.forename: Hong Lei
authors.initials: HL
authors.lastname: Zhang
authors.forename: Richard
authors.initials: R
authors.lastname: Watts
authors.forename: Martin R
authors.initials: MR
authors.lastname: Prince