AbstractDiagnostic accuracy of 64-slice CT angiography in the evaluation of in-stent restenosis is improved compared to previous CT methods. The image quality and exact diagnostic performance is, however, limited by several method, stent and patient-related factors. In this retrospective multicenter study the first results with dual source 64-slice scanner are presented in a Hungarian post PCI patient population (n=99). Radiation dose was 11.3±5.2 mSv (average±STD) using a helical scan. In 5.6% of all (n=142) examined stents clinicians were not able to give a final diagnosis using CT scan. This limitation showed correlation with the stent diameter. Nondiagnostic stents were smaller compared to the diagnostic stents (diameter 2.4±0.2 mm versus 3.2±0.5 mm, average±STD, respectively,P<0.01). Despite its high negative predictive value in the detection of restenosis, positive predictive value of CTA is lower, than that of invasive angiography. CT was not powerful enough in our study to distinguish vessel occlusion from severe restenosis. Heart rate was decreased by administration of intravenous metoprolol and in 75.8% of the patients scan was performed at a heart rate over 70 beats/minute, which did not have a significant influence on the diagnostic value.