Three-dimensional contrast-enhanced magnetic resonance angiography of carotid artery after stenting

This study presents 3-dimensional, contrast-enhanced, magnetic resonance (MR) angiographic appearances of the carotid artery after stenting.

The authors reviewed contrast-enhanced MR angiograms of 18 carotid arteries in 13 patients. These arteries were not stenotic or occluded in the stented segment, as shown on carotid angio-grams (11 patients) or carotid Doppler images (2 patients) obtained later.

Five patients had 1 stent in each of their bilateral carotid arteries. One patient with 1 stent in 1 artery underwent the examination twice with different MR coils. Different artifact patterns were found in 19 carotid-stent examinations. Type 1a involved short segments of false narrowing or false focal occlusion at both ends of the stent (n = 12); the carotid artery in the stented segment between the ends was normal. Types 2a and 2b occurred along the stented segment of the artery between the 2 ends of the stent. Type 2a was milder, with segmental faint signal intensity or luminal stenosis in the entire length of the stented segment (n = 5). Type 2b was total loss of luminal signal intensity over the whole length of the stented segment (n = 2). Last, type 1b was a band of hyperintensity at the ends of type 2a or 2b artifacts. Types 1a and 1b were due to susceptibility effect, and types 2a and 2b were from radio-frequency shielding effect. Both of these effects were identified in MR angiogram of nitinol stents and stainless steel stents.

Awareness of these artifacts is essential to prevent misdiagnosis.