Multidector CT Imaging of Coronary Artery Stent and Coronary Artery Bypass Graft

Coronary artery stenting has become the most important nonsurgical treatment for coronary artery disease. However, in-stent restenosis occurs at a relatively high rate and this problem has led to the routine use of invasive angiography for assessing stent patency. Although cor‐ onary angiography is the clinical gold standard and it is a very effective diagnostic tool for detecting such in-stent restenosis, it’s clearly an invasive procedure with its associated mor‐ bidity and mortality risks. Therefore, a noninvasive technique for detecting in-stent resteno‐ sis would be of great interest and use for following up patients after coronary angioplasty. Multidetector-row CT (MDCT) is being increasingly used for noninvasive coronary artery imaging as it has high diagnostic accuracy for detecting coronary artery stenosis in native, non-stented, coronary arteries. The recently introduced 64-slice CT offers more improved spatial and temporal resolution than does 4 and 16-slice CT and this results in superior visu‐ alization of the stent lumen and in-stent restenosis. However, although 64-slice MDCT al‐ lows for improved stent visualization, a relevant part (up to 47%) of the stent lumen is still not assessable (Mahnken et al., 2006). The metal of the stents can cause blooming artifacts that prevent the accurate interpretation of a lumen’s patency. To improve a stent’s visualiza‐ tion, numerous methods have been attempted such as dedicated post-processing or the use of dual-source CT. However, because of its presently limited sensitivity and high radiation exposure, MDCT should not be used as the first-line test to screen for in-stent restenosis in asymptomatic patients. Given its high specificity and negative predictive value, MDCT might be valuable for confirming stent occlusion in symptomatic patients.