Evaluation of In-Stent Restenosis by High Spatial Resolution CT

Multidetector row CT has been established as a noninvasive method for the detection of coronary artery disease. In previous studies, the diagnostic accuracy of 64-slice CT for the detection of in-stent restenosis usually displayed high sensitivity and negative predictive value, while specificity and positive predictive values were too low to allow its utilization in clinical practice. Especially in small stents-with a diameter below 3. 0 mm-the accuracy of CT angiography to detect in stent stenosis has been low. Recently, CT systems with improved in-plane spatial resolution (high-definition CT, HDCT) have become commercially available. Furthermore, an experimental CT (fine-cell detector CT, FDCT) has been developed using half pitch dimension detector cells in both X and Z directions compared with 64-slice CT. Compared with that in conventional 64-slice CT, the spatial resolution was 30% improved in HDCT and 60% improved in FDCT, and the lumen visibility was 1. 3 times improved in HDCT and 1. 5 times improved in FDCT. The diagnostic accuracy of in-stent restenosis with HDCT was higher than 90% in both sensitivity and specificity, moderate (77%) in positive predictive value, and very high (98%) in negative predictive value. FDCT is not yet applicable to patients, however, further improvement of diagnostic accuracy in the evaluation of in-stent restenosis is expected in FDCT. In the near future, cardiac CT could reach the diagnostic performance to replace invasive catheter angiography, and would be the appropriate noninvasive technique for diagnosis of in-stent restenosis.