PURPOSE: To assess the usefulness of 16-slice spiral CT for evaluation of restenosis of coronary artery stents. METHODS AND MATERIALS Consecutive 35 patients (20-80yrs, mean 58yrs) with coronary artery stents (n=48) were enrolled. Multi-detector CT (Sensation 16, Siemens, Germany) and invasive coronary arteriography were performed with interval from 1 to 22 days (mean 9 days). All patients were pre-treated with propranolol (30-60mg) prior to CT scan. CT parameters were 16x0.75mm collimation and 0.42s rotation speed. 120kV, 500 effective mA, and 3.4mm/rotation table-feed. Reconstruction window was tailored to individuals. Restenosis of in-stent lumen in CT was decided by presence of one of degraded stent shape, lower density of in-stent lumen than that of the proximal opacified vessel lumen, or absence of enhancement of the distal native vessel to the stent, in unaware of the results of invasive coronary arteriography. Accuracy was obtained comparing with the results of invasive coronary arteriography. RESULTS: Three stents (6%) of total 48 stents could not be evaluated with CT because of motion artifact (n=2) or complete obliteration of in-stent lumen by severe beam-hardening effect of stent (n=1) and were excluded. Twelve (26%) of 45 stents revealed restenosis by invasive coronary arteriography. Nine of twelve restenosis were correctly diagnosed with CT (Sensitivity 75%). These 9 stents showed lower in-stent density (n=9), severely degraded shape of stents (n=2), and absence of distal segment enhancement (n=1). One of 33 stents without restenosis was falsely diagnosed as restenosis with CT by equivocal lower density of in-stent lumen (Specificity 97%). The accuracy, positive predictive value, and negative predictive value were 91% (41/45), 90% (9/10), and 91% (32/35), respectively. Compared to mean (343.0짹78.7 HU) of the lowest pixel values of in-stent lumens without restenosis, extremely low density of in-stent lumen less than 110 HU was found only in 6 stents with restenosis. CONCLUSIONS: Visual assessment with measurement of in-stent luminal density is useful to evaluate the restenosis of coronary artery stents with 16-slice spiral CT.