In vitro evaluation of current thoracic aortic stent-grafts for real-time MR-guided placement.
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.
Eggebrecht
Holger
H
Department of Cardiology, West German Heart Center Essen, University of Duisburg-Essen, Germany. holger.eggebrecht@uni-essen.de
Zenge
Michael
M
Ladd
Mark E
ME
Erbel
Raimund
R
Quick
Harald H
HH
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
D000497:Alloys; C013616:nitinol