title: High-resolution renal MRA: comparison of image quality and vessel depiction with different parallel imaging acceleration factors.
abstract: OBJECTIVE
  To investigate the image quality and vessel depiction of renal MRA with integrated parallel imaging techniques (iPAT) using acceleration factors of 2 and 3.
  
  
  METHODS
  In this prospective study renal MRA was performed on 14 and 12 patients with acceleration factors of 3 and 2, respectively. For the MRA a 3D-GRE sequence with an acquired spatial resolution of 0.9 x 0.8 x 1.0 mm(3) was applied (TR/TE = 3.79 msec/1.39 msec, FOV = 400 mm x 320 mm, acquired matrix = 512 x 384, flip angle = 25 degrees) on a 32-channel 1.5T MR scanner. The acquisition time was 26 seconds with iPAT 2, and 19 seconds with iPAT3. All parameters other than acquisition time and acceleration factor were kept constant. To assess the signal-to-noise ratio (SNR) we performed repetitive phantom measurements using iPAT 2 and 3. The images were rated by two radiologists in terms of noise, artifacts, and the quality of vessel depiction for the proximal, segmental, and subsegmental renal artery. A Mann-Whitney U-test and kappa-test were used for statistical analysis.
  
  
  RESULTS
  SNR decreased significantly with iPAT 3 in the phantom measurements. The two readers found no difference in noise, but significantly fewer artifacts with iPAT 3. The depiction of segmental vessels was significantly better for both readers with iPAT 3, and the subsegmental vessels were rated significantly better by one reader. iPAT 3 also resulted in a better interreader agreement.
  
  
  CONCLUSIONS
  The use of iPAT 3 for renal MRA enables a better depiction of the distal parts of the renal artery. The decrease in SNR is not diagnostically impairing.
authors.affiliation: Department of Clinical Radiology, University Hospitals-Grosshadern, Ludwig Maximilians University, Munich, Germany. henrik.michaely@med.uni-muenchen.de
authors.forename: Henrik J
authors.initials: HJ
authors.lastname: Michaely
authors.forename: Karin A
authors.initials: KA
authors.lastname: Herrmann
authors.forename: Harald
authors.initials: H
authors.lastname: Kramer
authors.forename: Olaf
authors.initials: O
authors.lastname: Dietrich
authors.forename: Gerhard
authors.initials: G
authors.lastname: Laub
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Stefan O
authors.initials: SO
authors.lastname: Schoenberg
mesh_terms: D000328:Adult; D001808:Blood Vessels / Q000473:pathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D019047:Phantoms, Imaging; D011446:Prospective Studies; D012077:Renal Artery / Q000473:pathology; D012984:Software