Korean Circ J.  2007 Nov;37(11):521-529. 10.4070/kcj.2007.37.11.521.

Multidector CT Imaging of Coronary Artery Stents: Is This Method Ready for Use?

• Jung JI

• KMID: 1909612
• DOI: http://doi.org/10.4070/kcj.2007.37.11.521

Abstract

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 coronary 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 morbidity and mortality risks. Therefore, a noninvasive technique for detecting in-stent restenosis 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. However, the application of MDCT to stent imaging is somewhat difficult. It is generally accepted that visualizing the in-stent lumen with using 4-slice MDCT is impossible because of the modality's low temporal and spatial resolution. There is increased visualization of the stent lumen on 16-slice MDCT, and so in-stent restenosis can be detected in assessable stents. Yet for stents with small diameters (<3 mm) and/or thicker struts, visualization of instent stenosis remains a problem. The recently introduced 64-slice CT offers more improved spatial and temporal resolution than does 16-slice CT and this results in superior visualization of the stent lumen and in-stent restenosis. However, although 64-slice MDCT allows for improved stent visualization, a relevant part (up to 47%) of the stent lumen is still not assessable. There are many factors that interfere with the assessment of the real stent lumen even on 64-slice CT. The metal of the stents can cause blooming artifacts that prevent the accurate interpretation of a lumen's patency. The blooming effect is caused by a combination of partial volume averaging and beam hardening, and this results in higher CT attenuation values in the stent lumen and this enlarges the apparent size of the stent struts, thus leading to a pseudo-narrowing of the lumen. Regarding the type of stent, the gold or gold-coated stents along with the stents made of tantalum, cause the most severe artifacts, while the stainless steel and cobalt stents can be more accurately visualized. Cardiac motion, poor contrast filling, the oblique course of the coronary vessels and calcification may also decrease the ability to assess a stent's lumen. To improve a stent's visualization, 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. Such stent evaluation should focus on the proximal coronary artery segments and on those stents with a diameter greater than 3 mm.

Keyword

Multidetector row CT; Stents; Coronary stenosis

MeSH Terms

Angiography
Angioplasty
Artifacts
Cobalt
Constriction, Pathologic
Coronary Angiography
Coronary Artery Disease
Coronary Stenosis
Coronary Vessels*
Humans
Mortality
Sensitivity and Specificity
Stainless Steel
Stents*
Tantalum
Cobalt
Stainless Steel
Tantalum

Figure

• 

  Fig. 1 Stent (Cypher®) image with using 64-slice MDCT. A: multiplanar reformated (MPR) image of the left coronary artery clearly demonstrates the in-stent lumen and the internal enhancing vessel (arrow). B: the cross section image demonstrates the enhancing, patent stent in the vessel. MDCT: multidetector-row CT.

• 

  Fig. 2 In-stent restenosis image using 64-slice MDCT. A: the MPR image of the left circumflex artery shows lower attenuation inside the stent lumen (arrow) than that in the proximal artery. B: the cross sectional image obtained at the upper portion of the stent shows a patent enhancing vessel with an implanted stent. C: the cross sectional image obtained at the lower portion of the stent shows low attenuation within the stent, raising the possibility of in-stent occlusion. D: coronary angiography showed marked in-stent restenosis of the LCX (arrow). MDCT: multidetector-row CT, MPR: multiplanar reformatted, LCX: left circumflex artery.

• 

  Fig. 3 Variations of the severity of metal-related artifacts seen on 64-slice MDCT with variations of the metallic contents, the design and the luminal diameter of the stent. A: the MPR image shows two different stents in the LAD. Note the stent in the proximal LAD (Express®) shows more pronounced metal-related artifact than does the distal stent (Tetra®). B: cross section image of the proximal stent (Express®: 0.13 mm for the strut thickness). C: cross section image of the distal stent (Tetra®: 0.09-0.12 mm for the strut thickness). MDCT: multidetector-row CT, MPR: multiplanar reformatted, LAD: left anterior descending artery.

• 

  Fig. 4 Calcification hampers visualization of the in-stent lumen. A: continued stents at the proximal and mid LAD. Note the extensive calcifications at the stent of the mid LAD (arrow) prohibit the visualization of the in-stent lumen. B: the cross sectional image shows that calcification at the outer edge of the stent of the mid LAD contributes to beam hardening and this hampers visualization of the in-stent lumen. C: coronary angiography shows a patent LAD without any in-stent stenosis. LAD: left anterior descending artery.

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