Coronary stent assessment on multidetector computed tomography: source and predictors of image distortion

Metallic stent struts cause imaging artifacts on multidetector computed tomography (MDCT) which interfere with the assessment of in-stent coronary restenosis. We examined the degree of image distortion of implanted coronary stents on MDCT, comparing different stent types, sizes and orientation.

We quantified stent dimensions and image distortion of 151 non-opacified coronary stents in 89 patients (81% men, age 65+/-10 years) who underwent MDCT with a 40 slice MDCT scanner. Stent dimension by MDCT was compared with measurements obtained from quantitative coronary angiographic (QCA) in the immediate post-implantation angiogram and with manufacturers' data.

Stent image quality was good for 107 stents (71%), moderate for 38 (25%) and poor in 6 (4%), 2 (<1%) of which were not assessable. Blooming artifact resulted in a mean MDCT luminal (inner) diameter 30+/-14% smaller than QCA diameter (2.0+/-0.5 vs 2.9+/-0.3 mm, p<0.001) and a mean outer diameter exceeding QCA by 31+/-14% (3.8+/-0.5 vs 2.9+/-0.3 mm, p<0.001). MDCT luminal stent diameter was unrelated to strut thickness or the vessel stented but appeared to be smaller for vertically orientated stents (p=0.017), cobalt alloy (vs stainless steel) (p=0.011) and also for different stent types (p=0.006).

The luminal dimension of implanted coronary stents, as visualized with 40 slice MDCT, was one third smaller than on invasive angiography. This decrease in visualized stent luminal diameter forms the basis for the difficulty in accurate assessment of in-stent restenosis by MDCT.