0 tesla contrast-enhanced mr angiography of carotid artery stents : in vitro measurements as compared with 1 . 5 tesla

Background and Purpose: To assess the appearance of carotid artery stents at 3.0Tesla contrast enhanced magnetic resonance angiography (CE-MRA) as compared with 1.5Tesla. Methods: 19 stents (GUIDANT Acculink, GUIDANT Dynalink, BOSTON SCIENTIFIC SMART Neuroform, GUIDANT Omnilink, EV3 Protege, BOSTON SCIENTIFIC Carotid Wallstent, ABBOTT Xact) of different materials (nitinol, stainless steal, cobalt alloy) and different sizes (4.0mm-10.0mm) were investigated regarding their appearance on CE-MRA at 3.0Tesla and at 1.5 Tesla. For each stent artificial lumen narrowing (ALN) was calculated based on a pixel-bypixel profile of the contrast-to-noise-ratio giving an objective indicator for the size of the evaluable stent diameter. Results: Only in two stents (Omnilink 7.0mm, Omnilink 10.0mm) was ALN higher at 3.0Tesla relative to 1.5Tesla. In all other stents ALN at 3.0Tesla was the same or even lower as compared with 1.5Tesla. In contrast to the ferromagnetic stents where ALN was typically higher than 85%, in most of the nitinol stents (Acculink, Dynalink, Neuroform, Protege) ALN was below 35%. In the Xact stents ALN was generally 100% at 1.5Tesla and ranged between 31.8% and 100% at 3.0Tesla. Conclusion: CE-MRA after carotid artery stenting is considerably impaired by ALN both at 1.5Tesla and at 3.0Tesla. Nevertheless, CE-MRA is well suited for the examination of carotid artery stents made of nitinol at both field strengths. Stent manufacturers should be aware of potential artifacts caused by their stents during noninvasive diagnostic methods such as CE-MRA.