title: Renal magnetic resonance angiography at 3.0 Tesla using a 32-element phased-array coil system and parallel imaging in 2 directions.
abstract: OBJECTIVE
  The aim of the present study was to assess the feasibility of renal magnetic resonance angiography at 3.0 T using a phased-array coil system with 32-coil elements. Specifically, high parallel imaging factors were used for an increased spatial resolution and anatomic coverage of the whole abdomen.
  
  
  METHODS
  Signal-to-noise values and the g-factor distribution of the 32 element coil were examined in phantom studies for the magnetic resonance angiography (MRA) sequence. Eleven volunteers (6 men, median age of 30.0 years) were examined on a 3.0-T MR scanner (Magnetom Trio, Siemens Medical Solutions, Malvern, PA) using a 32-element phased-array coil (prototype from In vivo Corp.). Contrast-enhanced 3D-MRA (TR 2.95 milliseconds, TE 1.12 milliseconds, flip angle 25-30 degrees , bandwidth 650 Hz/pixel) was acquired with integrated generalized autocalibrating partially parallel acquisition (GRAPPA), in both phase- and slice-encoding direction. Images were assessed by 2 independent observers with regard to image quality, noise and presence of artifacts.
  
  
  RESULTS
  Signal-to-noise levels of 22.2 +/- 22.0 and 57.9 +/- 49.0 were measured with (GRAPPAx6) and without parallel-imaging, respectively. The mean g-factor of the 32-element coil for GRAPPA with an acceleration of 3 and 2 in the phase-encoding and slice-encoding direction, respectively, was 1.61. High image quality was found in 9 of 11 volunteers (2.6 +/- 0.8) with good overall interobserver agreement (k = 0.87). Relatively low image quality with higher noise levels were encountered in 2 volunteers.
  
  
  CONCLUSIONS
  MRA at 3.0 T using a 32-element phased-array coil is feasible in healthy volunteers. High diagnostic image quality and extended anatomic coverage could be achieved with application of high parallel imaging factors.
authors.affiliation: Department of Diagnostic Radiology, Eberhard-Karls-University Tuebingen, Hoppe-Seyler-Strasse 3, 72076 Tuebingen, Germany. michael.fenchel@med.uni-tuebingen.de
authors.forename: Michael
authors.initials: M
authors.lastname: Fenchel
authors.forename: Kambiz
authors.initials: K
authors.lastname: Nael
authors.forename: Vibhas S
authors.initials: VS
authors.lastname: Deshpande
authors.forename: J Paul
authors.initials: JP
authors.lastname: Finn
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kramer
authors.forename: Stephan
authors.initials: S
authors.lastname: Miller
authors.forename: Stefan
authors.initials: S
authors.lastname: Ruehm
authors.forename: Gerhard
authors.initials: G
authors.lastname: Laub
mesh_terms: D000328:Adult; D000368:Aged; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007668:Kidney / Q000098:blood supply* / Q000473:pathology*; D018810:Magnetic Resonance Angiography / Q000295:instrumentation* / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media