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Quantification and Detectability of In-Stent Stenosis with CT Angiography and MR Angiography in Arterial Stents In Vitro

¹ All authors: Division of Angiography and Interventional Radiology, Department of Radiology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria.

OBJECTIVE. The purpose of this study was to compare CT angiography (CTA) and MR angiography (MRA) for the detectability of 75% and 95% stenoses in phantoms using six different stents.

MATERIALS AND METHODS. Six different stents (Expander, Hemobahn, SelfX, Smart, Symphony, and Wallstent) were inserted into tubes filled with contrast agent (ioversol or gadoteric acid). To mimic stenoses of 75% and 95% of the patent lumen, 8-mm-diameter nylon cylinders were bored in the central axis (2 mm and 4 mm, respectively) and placed into the stent lumen. Intensity profiles across stenoses on 2-mm coronal reformatted sections of CTA or MRA were compared, and the detectability of the residual lumen was assessed using a subjective score.

RESULTS. CTA showed relative in-stent signal attenuation for the in-stent stenoses of the tested stents ranging from 75% to 100% of the signal intensity of the control. SelfX and Symphony showed further shading of the residual lumen due to beam-hardening artifacts. Overestimation of stenosis was associated with low-grade stenoses in which the border of the lumen was closer to the stent struts. MRA showed relative in-stent signal attenuation of the in-stent stenoses ranging from 30% to 100% of the signal intensity of the control. Strut thickness tended to correlate with higher attenuation at CT.

CONCLUSION. CTA may be more suitable for differentiation between 95% stenosis and occlusion; MRA has higher sensitivity in detecting 75% stenoses. Strut thickness and mesh size did not prove to be significant predictors for signal attenuation or overall image quality.

Keywords: CT • in-stent restenosis • in vitro • MRI • stenosis

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