title: 3.0 Tesla magnetic resonance angiography of endovascular aortic stent grafts: phantom measurements in comparison with 1.5 Tesla.
abstract: OBJECTIVE
  This study evaluated different stent grafts by 3 T magnetic resonance angiography (MRA) with respect to lumen visibility, susceptibility-induced signal loss, and type of stent artifacts compared with 1.5 T MRA in a phantom model.
  
  
  METHODS
  Six different stent-grafts (tube: n = 3, bifurcated: n = 3) were evaluated by 3 T and 1.5 T MRA using a tube phantom. MRA was performed using T1-weighted sequences at both systems with comparable parameters (3T: TR 5.4/TE 2.0/FA 30 degrees, 1.5 T: TR 6.2/TE 2.2/FA 30 degrees). A blind study of the image quality, including artifacts, was performed by 3 radiologists. Furthermore, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values were calculated. Statistical analysis was performed with Student's t test (P < 0.05).
  
  
  RESULTS
  One Elgiloy stent graft showed almost a complete intraluminal signal loss at 1.5 and 3 T. All other models could be evaluated by both systems by MRA, resulting in a favorable lumen visibility (score: 1) for prostheses made of nitinol. Scores for overall image quality and artifacts were the same for both MR systems. SNR and CNR values of the stented part of the vessel phantom increased from 320 +/- 33 to 618 +/- 40 and from 306 +/- 34 to 596 +/- 40 at 3 T when compared with 1.5 T, resulting in a significant signal gain of 93% at the higher field strength.
  
  
  CONCLUSIONS
  3 Tesla MRA of aortic stent grafts in a phantom model demonstrates an increase in SNR and CNR when compared with 1.5 T. However, the magnitude of imaging artifacts as well as coherent intraluminal signal loss within the stent does not increase equally in both MR systems.
authors.affiliation: Institut fur Klinische Radiologie, Rontgendiagnostik, Universitatsklinikum, Munster, Germany. kraemers@uni-muenster.de
authors.forename: Stefan C
authors.initials: SC
authors.lastname: Krämer
authors.forename: Alexander
authors.initials: A
authors.lastname: Wall
authors.forename: David
authors.initials: D
authors.lastname: Maintz
authors.forename: Rainald
authors.initials: R
authors.lastname: Bachmann
authors.forename: Harald
authors.initials: H
authors.lastname: Kugel
authors.forename: Walter
authors.initials: W
authors.lastname: Heindel
mesh_terms: D001011:Aorta; D016477:Artifacts; D018810:Magnetic Resonance Angiography / Q000379:methods*; D019047:Phantoms, Imaging; D015607:Stents