CT and MR imaging of nitinol stents with radiopaque distal markers.
OBJECTIVE
To evaluate imaging characteristics and artifacts of a nitinol stent with distal tantalum markers with computed tomography (CT) angiography and magnetic resonance (MR) angiography.


METHODS
A vascular phantom was built to simulate in-stent restenosis. A nitinol stent with tantalum markers (Luminexx stent) was evaluated with CT angiography in different orientations relative to the z-axis and with MR angiography in different positions relative to both B0 and the readout gradient. Stenosis measurements were compared with conventional digital subtraction angiography for both modalities. In-stent signal intensity obtained with different flip angles was assessed in two nitinol stents with distal markers (Luminexx stent and SMART stent) and one without markers (Memotherm-FLEXX stent).


RESULTS
Stenosis detection was not possible with CT angiography when the stent was perpendicular to the z-axis because of streak-like artifacts induced by tantalum markers. Stenosis evaluation with multiplanar reformation was accurate when the stent was in parallel and oblique orientations relative to the table axis. With MR angiography, metallic artifacts were mostly related to the stent orientation with B0, whereas orientation of the readout gradient had little influence. The mean error (overestimation) for stenosis measurements varied between 0.1% and 7.4% for CT imaging in parallel and oblique positions and 3.6% and 9.5% for MR imaging. Higher flip angles did not improve signal intensity inside the three stents tested.


CONCLUSIONS
CT and MR angiography can be used for evaluating the patency of stents with distal markers that are parallel or oblique relative to the table axis (iliac, carotid, or femoral stents). MR angiography is preferred if the stent is perpendicular to the table axis (renal stent).
Létourneau-Guillon
Laurent
L
Department of Radiology, CHUM-Notre-Dame Hospital, 1560 Sherbrooke East, Montreal, Quebec, Canada, H2L 4M1. cbinkert@partners.org
Soulez
Gilles
G
Beaudoin
Gilles
G
Oliva
Vincent L
VL
Giroux
Marie-France
MF
Qin
Zhao
Z
Boussion
Nicolas
N
Therasse
Eric
E
De Guise
Jacques
J
Cloutier
Guy
G
D000497:Alloys; D015901:Angiography, Digital Subtraction; D016477:Artifacts; D003287:Contrast Media; D006083:Graft Occlusion, Vascular / Q000175:diagnosis* / Q000000981:diagnostic imaging; D007091:Image Processing, Computer-Assisted; D007482:Iothalamate Meglumine; D018810:Magnetic Resonance Angiography; D019047:Phantoms, Imaging; D015607:Stents; D013635:Tantalum; D014057:Tomography, X-Ray Computed
D000497:Alloys; D003287:Contrast Media; C013616:nitinol; D013635:Tantalum; D007482:Iothalamate Meglumine