[MRI of carotid stents: influence of stent properties and sequence parameters on visualization of the carotid artery lumen].
OBJECTIVE
To evaluate MR artifacts of carotid artery stents and to optimize stent properties and sequence parameters.


METHODS
Four carotid artery stents - Wallstent (mediloy), Precise (nitinol), ACCULINK (nitinol) and a stent prototype (nitinol) - were investigated in a flow model of the cervical vessels. The model was made of silicon tubing and a flow pump that produces realistic flow curves of the carotid artery. To investigate the effects of magnetic susceptibility and radiofrequency induced shielding artifacts, turbo spin echo and gradient echo sequences as well as CE-MRAs were measured. To improve the visualization of the stent lumen in a CE-MRA, flip angle as well as geometry and covering of the stent prototype were altered.


RESULTS
Susceptibility artifacts in stents of the carotid artery only influence the lumen visualization at the proximal and distal end of the braided mediloy stent. A change of stent coverings has no significant influence on radiofrequency artifacts, whereas a reduction in linking elements between stent segments and a change in diameter of stent struts improves visualization of the stent lumen. By increasing the flip angle in a CE-MRA, visualization of the stent lumen is possible in both mediloy and nitinol stents.


CONCLUSIONS
The choice of stent material and changes in stent geometry as well as the optimization of the flip angle of the CE-MRA may reduce susceptibility and radiofrequency artifacts, rendering feasible the CE-MRA of a stented carotid artery.
Straube
T
T
Sektion Neuroradiologie der Klinik für Neurochirurgie, Christian Albrechts Universität Kiel. straubetwi@aol.com
Wolf
S
S
Flesser
A
A
Deli
M
M
Alfke
K
K
Nabavi
A
A
Jansen
O
O
D000497:Alloys; D016477:Artifacts; D002339:Carotid Arteries; D005240:Feasibility Studies; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008953:Models, Anatomic; D015607:Stents
D000497:Alloys; C013616:nitinol