title: In vitro evaluation of current thoracic aortic stent-grafts for real-time MR-guided placement.
abstract: OBJECTIVE
  To systematically evaluate the magnetic resonance imaging (MRI) characteristics of current thoracic aortic stent-graft devices before, during, and after in vitro deployment as a step toward real-time MRI-guided stent placement.
  
  
  METHODS
  Six stent-graft devices used for thoracic aortic repair were examined in a dedicated phantom model using a 1.5-T MRI scanner. First, the delivery systems with the mounted stent-graft were examined using real-time fast imaging with steady-state precession (TrueFISP) with Cartesian and radial k-space filling. TrueFISP imaging was subsequently used for real-time monitoring of stent-graft expansion. The deployed stent-grafts were then examined in a water bath containing gadolinium (1:40) with high-resolution T1-weighted 3D fast low-angle shot (FLASH) sequences. The images were analyzed for artifacts, radiofrequency caging effects, and device visualization quality.
  
  
  RESULTS
  Three delivery systems with mounted stent-grafts did not contain ferromagnetic elements and were well visualized. Imaging with radial k-space filling showed fewer artifacts than Cartesian imaging. Movement of the delivery system and stent-graft expansion of these devices were successfully demonstrated at a rate of up to 6 frames per second. Evaluation of the expanded stent-grafts revealed only minor susceptibility artifacts without relevant signal attenuation in the stent-graft lumen for 5 nitinol-based stent-grafts. Only a stainless steel-based stent-graft was associated with severe artifacts, thwarting visualization of its lumen or surroundings.
  
  
  CONCLUSIONS
  The present study shows that 3 nitinol-based thoracic stent-graft devices are potentially suited for real-time MRI-guided placement with respect to both the delivery system and the stent-graft itself. These observations provide the basis for the evaluation of MRI-guided stent-graft placement in vivo.
authors.affiliation: Department of Cardiology, West German Heart Center Essen, University of Duisburg-Essen, Germany. holger.eggebrecht@uni-essen.de
authors.forename: Holger
authors.initials: H
authors.lastname: Eggebrecht
authors.forename: Michael
authors.initials: M
authors.lastname: Zenge
authors.forename: Mark E
authors.initials: ME
authors.lastname: Ladd
authors.forename: Raimund
authors.initials: R
authors.lastname: Erbel
authors.forename: Harald H
authors.initials: HH
authors.lastname: Quick
mesh_terms: D000497:Alloys; D001013:Aorta, Thoracic; D016477:Artifacts; D019917:Blood Vessel Prosthesis Implantation / Q000379:methods*; D002406:Catheterization, Peripheral; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D019060:Minimally Invasive Surgical Procedures; D019047:Phantoms, Imaging; D015607:Stents
chemical_list: D000497:Alloys; C013616:nitinol