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In vitro evaluation of metallic coronary artery stents with 64-MDCT using an ECG-gated cardiac phantom: relationship between in-stent visualization, stent type, and heart rate.

OBJECTIVE
The purpose of this study was to assess the accuracy of 64-MDCT in the visualization of different coronary artery stents and in the appraisal of in-stent stenosis.


MATERIALS AND METHODS
Five different coronary stent types with three diameters (2.5, 3.0, and 4.0 mm) were analyzed using anthropomorphic dynamic cardiac phantom. All stents were mounted on polyurethane sticks of defined outer diameter and contained a default concentric stenosis of 50% each. Imaging was performed at four different heart rates (no motion, 60 beats/min, 75 beats/min, and 90 beats/min). Apparent stent diameter, degree of stenosis, in-stent attenuation, and diagnostic accuracy were assessed.


RESULTS
A significant (p < 0.05) overestimation of the degree of stenosis (41.1% +/- 41.4%), underestimation of the stent lumen (-42.7% +/- 41.4%), and increase in in-stent attenuation (36.6 +/- 29.2 HU) were observed for all stents and heart rates. In-stent stenosis > 50% was detected with an overall sensitivity of 88.9% (95% CI, 75.9-96.3%) and an overall specificity of 51.1% (95% CI, 35.8-66.3%) by observer 1 and with an overall sensitivity of 86.7% (95% CI, 73.2-94.9%) and an overall specificity of 57.8% (95% CI, 42.2-72.3%) by observer 2. A trend toward higher specificity was observed for increasing stent diameter, however, without reaching statistical significance (p = 0.63).


CONCLUSION
In an experimental setting, 64-MDCT allows a reliable detection of instent stenosis but significantly overestimates the actual degree of stenosis. Within the range of physiologic heart rates, diagnostic accuracy is restricted by spatial, not temporal, resolution.