Original Article
Comparison of 16-Slice Computed Tomography with Conventional Angiography to Evaluate Coronary Artery Stent Patency Koroner Arter Stentlerinde Patensinin Belirlenmesinde 16 Dedektörlü Bilgisayarlı Tomografi ile Konvansiyonel Anjiyografi Bulgularının Karşılaştırılması Irmak Durur-Subasi1, Mecit Kantarci2, Afak Durur-Karakaya2, Adnan Okur2 1
Yozgat State Hospital, Department of Radiology, Yozgat, Turkey Ataturk University, Faculty of Medicine, Department of Radiology, Erzurum, Turkey
2
Correspondence to: Dr. Irmak Durur-Subasi, Yozgat State Hospital, Department of Radiology, 66000 Yozgat, Turkey. Phone: +90.354.2171060-1181, Fax: +90.354.2126309, e-mail: [email protected]
Abstract
Özet
Objective. In this study, we evaluated the utility of 16-slice MDCT (multidetector computed tomography) to assess stent patency after coronary artery stenting.
Amaç. Bu çalışmada koroner arter stentlerinde 16 kesitli bilgisayarlı tomografinin (BT) stent içi lümeni değerlendirmedeki rolünü inceledik.
Materials and Methods. Retrospective ECG-gated CT-angiography using 16-slice MDCT was performed in 52 consecutive patients with coronary artery stents. Qualitative assessment of 61 coronary stent lumens by MDCT is reported, and the reasons preventing assessment were investigated.
Gereç ve Yöntem. Koroner arter stenti yerleştirilmiş sıralı 52 hasta (61 stent), retrospektif elektrokardiyografi (EKG) kapılı BT anjiyografi ile incelendi. Altmış bir stentin lümenlerinin çok kesitli bilgisayarlı tomografi (ÇKBT) ile değerlendirilebilirliği nitel olarak gözden geçirildi ve değerlendirilemez görüntülerin sebepleri araştırıldı.
Results. All non-assessable stents were non-assessable due to partial volume effects and metal artifacts. To evaluate instent restenosis, conventional coronary angiography was performed on the 54 assessable stents in 48 patients, and the results were compared with the MDCT results. Based on the results of the conventional coronary angiography, MDCT correctly detected four in-stent restenosis. Conclusion. Despite some limitations, 16-slice MDCT provides sufficient evaluations of some coronary stents, and can detect in-stent restenosis with high accuracy.
Keywords: Coronary artery stents, Lumen patency, MDCT
The Eurasian Journal of Medicine
Bulgular. Değerlendirilemez görüntülere kısmi hacim etkileri ve metal artefaktları neden olmuştu. Ayrıca stent içi restenoz açısından değerlendirilebilir görüntülere sahip 48 hastadaki 54 stent, konvansiyonel koroner anjiyografi ile tetkik edilerek sonuçlar karşılaştırıldı. Konvansiyonel koroner anjiyografi ile karşılaştırıldığında ÇKBT koroner anjiyografi 4 stentte stent içi restenozu doğru bir şekilde tanıyabilmişti. Sonuç. Bazı sınırlılıklarına rağmen 16 kesitli bilgisayarlı tomografi koroner arter stentlerinin incelenmesinde yeterince yararlı bir yöntemdir. ÇKBT değerlendirilebilir görüntüler elde edildiğinde konvansiyonel koroner anjiyografi ile karşılaştırılabilir düzeyde yüksek doğruluğa sahip sonuçlar verebilmektedir. Anahtar Kelimeler: Koroner arter stentleri, Lümen açıklığı, ÇKBT
4
Subasi et al.
Introduction
T
he development of multidetector computed tomography (MDCT) has enabled visualization of coronary arteries with acceptable temporal and spatial resolution. MDCT has recently been used to evaluate coronary arteries, coronary plaques and coronary bypass grafts [1–8]. In this study, we investigated the utility of 16-slice MDCT in coronary stent visualization, the possible drawbacks and the accuracy of diagnosing in-stent re-stenosis compared to conventional coronary angiography.
Fig. 1
_
An axial contrast-enhanced CT image shows a 2.5 mm stent in the proximal segment of the LAD. The lumen cannot be visualized for partial volume effects.
Fig. 1
Patients and Methods Fifty-two consecutive patients (20-77 years old, mean 52.8 years, 48 males) with coronary artery stents, who could hold their breath long enough, and had no cardiac arrhythmia, were evaluated via retrospective ECG-gated CTangiography using 16-slice MDCT. Sixty-one (61) total stents were assessed. Patients with arrhythmia, renal insufficiency, intravenous contrast allergy, poor general health status, an inability to hold their breath for an extended period, x-ray contraindication, inability to cooperate during the scan, or a heart rate greater than 90 beats per minute were excluded from the study. Examinations were performed with a 16-slice scanner (Aquillon, Toshiba Medical Systems; Tokyo, Japan) during one breath-hold with the following parameters: 16 x 0.5 mm collimation, 1.0 mm detector thickness and 1.0 mm reconstruction interval. After acquisition, images were reconstructed with an R-R interval between 50% and 90% in 5% increments and were transferred to a workstation (Vitrea2, Vital Images; Minneapolis, MN, USA) for image analysis In addition to axial resource images, multiplanar reconstructions, curved multiplanar reformations, maximum intensity projection (MIP) images and 3D images were investigated for patency and re-stenosis. Two radiologists deemed the images sufficient or insufficient for each stent with regards to luminal patency and in-stent re-stenosis. If the lumen could be seen and was free of metal, motion or calcium artifacts, the images was accepted as sufficient. The reasons for insuffi-
EAJM: 41, April 2009
Fig. 2
_ Anterior view
of 3D volume rendering images shows a 3 mm stent in the middle segment of the RCA. The lumen cannot be visualized due to motion artifacts.
Fig. 2
cient images were examined. When vessel segments distal to the stent implantation region did not enhance, occlusion was diagnosed. Significant low density in the stent implantation region indicated in-stent re-stenosis. On the other hand, a homogenous intraluminal contrast density with similar contrast density to reference regions (e.g., proximal or distal of stent) indicated stent patency. Conventional angiography was performed by an interventional cardiologist with at least five years of experience who had no information about the MDCT angiography results. Stents with sufficient data from the MDCT angiography were also evaluated by conventional angiography for luminal patency and possible re-stenosis. The results of both modalities were compared. MDCT angiography and conventional angiography were performed within three days of each other.
5
Coronary Artery Stents Imaging with MDCT
A Fig. 3
B
C
_ 3.5 x 18.5 mm stent in the proximal segment of the LAD. In axial oblique MIP (A), vessel probe (B) and conventional angiography (C) images, luminal
patency is seen.
Results
angiography. MDCT correctly determined the luminal patency of the remaining 50 stents.
Fifty-two (52) consecutive patients (20-77 years old, mean 52.8 years, 48 male) with coronary artery stents underwent MDCT coronary angiography in our department with no complications. In total, 61 stents were evaluated; 54 of the stents (88.5%) were found to be sufficient, and 7 (11.5%) were insufficient. Reasons for insufficient imaging included motion artifacts, partial volume effects and metal artifacts. Based on caliber, stents wider than 3.5 mm had a higher rate of sufficient imaging (43/45, 95.5%). Three (3.0)-millimeter stents had a lower rate of sufficient imaging secondary to metal and motion artifacts (11/14, 78.6%). Notably, 2.5-mm stents (two stents) were not evaluated for metal artifacts and partial volume effects (Table 1) (Figures 1-7).
Discussion Coronary artery disease has been increasingly treated with percutaneous angioplasty and intracoronary stent placement. Although stent deployment significantly reduces the re-stenosis rate when compared to balloon angioplasty, 30% of cases may have neointimal proliferation, which leads to restenosis [9–12]. Conventional angiography is the gold standard for detecting re-stenosis. Although it is an effective diagnostic tool, it is associated with significant morbidity (1.7%) and mortality (0.11%). Moreover, it is an invasive method that requires hospitalization [13].
Forty-eight (48) patients with 54 stents assessable by MDCT coronary angiography underwent conventional angiography. Four cases exhibited in-stent re-stenosis, which were observed via conventional angiography and MDCT coronary
Thus, several other methods have been evaluated to identify in-stent re-stenosis. However, neither magnetic resonance imaging nor electron beam tomography has provided sufficient imaging of the lumen [14,15]. With MDCT, iliac and
A Fig. 4
B
C
_ Two stents (3.5 mm) in the proximal and middle segments of the LAD. Axial oblique MIP (A), vessel probe (B) and conventional angiography (C)
images show the luminal patency.
EAJM: 41, April 2009
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Subasi et al.
Fig. 5 A
Krüger et al. studied 20 patients with coronary stents using four-slice computed tomography and reported that the stent lumens could not be visualized [18]. In another study using four-slice CT, Maintz et al. reported that 58% of the stents were assessable, and they calculated 100% sensitivity and 50% specificity in defining in-stent re-stenosis [19]. Schuijf et al. studied 22 patients with 16-slice MDCT, and they found 77% of the stents were assessable, with 78% sensitivity and 100% specificity for detecting in-stent re-stenosis [20]. Ohnuki et al. reported 95% of stents were assessable with 75% sensitivity and 88% specificity with this technique [21]. Similarly, Cademartiri et al. reported that all stents in 51 patients were assessable, and they calculated 69% sensitivity and 95% specificity [22], while Gilarda et al. studied 143 patients, and observed that 64% of the stents were assessable with 54% sensitivity and 100% specificity. In our study, we
A Fig. 6
ment of the LAD. Axial oblique MIP (A) and 3D volume rendering (B) images show luminal patency.
B
carotid stent lumens, and even neointimal hyperplasia, have been shown [16,17]. For smaller vessels (e.g., coronary or cerebral arteries) imaging of the lumen, neointimal hyperplasia or in-stent re-stenosis is more challenging.
B
_ 3.5 x 22 mm stent in the middle seg-
were able to assess 88.5% of the stents, and four stents with re-stenosis were also confirmed by conventional angiography. In our study, there was a connection between the level of stent metal artifacts and stent caliber. Metal in the stent strut absorbs x-ray and leads to beam hardening and high-density artifacts. This false narrowing causes misinterpretation. Tantalum has been reported to have more metal artifacts and therefore should not be evaluated with MDCT [23]. In addition, stents with gold markers (e.g., Bestent2) were reported to be poorly evaluated in this study, and thicker stent struts increased the incidence of metal artifacts in the same study [24,25]. For 3 mm or smaller caliber stents, partial volume effects and metal artifacts poisoned the luminal image, and 2.5 mm caliber stents cannot be imaged by 16-slice CT at all. Heart motion artifacts and severe calcifications prevented stent imaging. Heart motion artifacts especially influence stents located in right coronary artery (RCA) (chiefly segment 2). Calcifications in the proximal portion of the left anterior
C
_
3.5 x 16 mm and a 4 x 9 mm stent in the middle segment of the left circumflex (LCx). Coronal oblique MIP (A), 3D volume rendering (B) and vessel probe (C) images show the patent stent.
EAJM: 41, April 2009
7
Coronary Artery Stents Imaging with MDCT
_
Fig. 7 3.5 x 16 mm stent in the proximal portion of an aorta (Ao)-LCx free saphenous graft. Axial oblique MIP (A) and 3D volume rendering (B) images show the patent stent.
A
B
descending artery (LAD) are potentially more dense and affect stents located in segment 6. In our study, we showed that, in four assessable stents, MDCT determined in-stent re-stenosis with 100% accuracy, as confirmed via conventional angiography. Detecting restenosis after stent deployment is of great clinical importance, as re-stenosis may develop in up to 46% of stents within the first 6 months [26]. When a patient presents to a physician with angina after stent deployment, invasive conventional angiography may be needed. As the population who undergoes
coronary artery stenting increases, non-invasive imaging of the luminal patency in these patients is needed. With its high specificity and negative predictive value, MDCT coronary angiography should enter into routine clinical practice, thereby preventing unnecessary cardiac catheterization. Conventional angiography with high spatial resolution is the gold standard for imaging coronary arteries, but it cannot show the vessel wall. MDCT coronary angiography will thus play an important role in future coronary artery stent imaging with its high spatial resolution and rapid acquisition.
Conflict interest statement The authors declare that they have no conflict of interest to the publication of this article.
References 1. Kachelriess M, Kalender WA. Electrocardiogram-correlated image reconstruction from subsecond spiral computed tomography scans of the heart. Med Phys 1998; 25: 2417–31. 2. Ohnesorge B, Flohr T, Becker C et al. Cardiac imaging by means of electrocardiographically gated multisection spiral CT: initial experience. Radiology 2000; 217: 564–71. 3. Nieman K, Oudkerk M, Rensing BJ et al. Coronary angiography with multi-slice computed tomography. Lancet 2001; 357: 599–603. 4. Achenbach S, Giesler T, Ropers D et al. Detection of coronary artery stenosis by contrast-enhanced, retrospectively electrocardiographically gated, multislice spiral computed tomography. Circulation 2001; 103: 2535– 8. 5. Knez A, Becker CR, Leber A et al. Usefulness of multislice spiral computed tomography angiography for determination of coronary artery stenosis. Am J Cardiol 2001; 88: 1191–4. 6. Schroeder S, Kuettner A, Kopp AF et al. Noninvasive evaluation of the prevalence of noncalcified atherosclerotic plaques by multi-slice detector computed tomography: results of a pilot study. Int J Cardiol 2003; 92: 151–5. 7. Leber AW, Knez A, Becker A et al. Accuracy
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of multidetector spiral computed tomography in identifying and differentiating the composition of coronary atherosclerotic plaques. J Am Coll Cardiol 2004; 43: 1241–7. Burgstahler C, Kuettner A, Kopp AF et al. Non-invasive evaluation of coronary artery bypass grafts using multi-slice computed tomography: initial clinical experience. Int J Cardiol 2003; 90: 275– 80. Serruys PW, de Jaegere P, Kiemeneij F et al. A comparison of balloon-expandable-stent implantation with balloon angioplasty in patients with coronary artery disease. N Engl J Med 1994; 331: 489–95. Fischman DL, Leon MB, Baim DS et al. Stent Restenosis Study Investigators. A randomized comparison of coronary-stent placement and balloon angioplasty in the treatment of coronary artery disease. N Engl J Med 1994; 331: 496–501. Serruys PW, Degertekin M, Tanabe K et al. Intravascular ultrasound findings in the multicenter, randomized, double-blind RAVEL (RAndomized study with the sirolimus-eluting VElocity balloon-expandable stent in the treatment of patients with de novo native coro-
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nary artery Lesions) trial. Circulation 2002; 106: 798–803. Serruys PW, Degertekin M, Tanabe K et al. Vascular responses at proximal and distal edges of paclitaxel-eluting stents: serial intravascular ultrasound analysis from the TAXUS II trial. Circulation 2004; 109: 627–33. Scanlon PJ, Faxon DP, Audet AM, et al. ACC/ AHA guidelines for coronary angiography. A report of the American College of Cardiology/American Heart Association Task Force on practice guidelines (Committee on Coronary Angiography). Developed in collaboration with the Society for Cardiac Angiography and Interventions. Circulation 1999; 99: 2345–57. Pump H, Möhlenkamp S, Sehnert CA et al. Coronary arterial stent patency: assessment with electron-beam CT. Radiology 2000; 214: 447–52. Maintz D, Botnar RM, Fischbach R et al. Coronary magnetic resonance angiography for assessment of the stent lumen: a phantom study. J Cardiovasc Magn Reson 2002; 4:359–67
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16. Maintz D, Fischbach R, Juergens K, Allkemper T, Wessling J, Heindel W. Multislice CT-angiography of the iliac arteries in the presence of various stents: in vitro evaluation of artifacts and lumen visibility. Invest Radiol 2001; 36: 699–704. 17. Cademartiri F, Mollet N, Nieman K, Krestin GP, de Feyter PJ. Images in cardiovascular medicine. Neointimal hyperplasia in carotid stent detected with multislice computed tomography. Circulation 2003; 108-147. 18. Kruger S, Mahnken AH, Sinha AM et al. Multislice spiral computed tomography for the detection of coronary stent restenosis and patency. Int J Cardiol 2003; 89: 167–72. 19. Maintz D, Grude M, Fallenberg EM, Heindel W, Fischbach R. Assessment of coronary arte-
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rial stents by multislice-CT angiography. Acta Radiol 2003; 44: 597–603. Schuijf JD, Bax JJ, Jukema JW et al. Feasibility of assessment of coronary stent patency using 16-slice computed tomography. Am J Cardiol 2004; 94: 427–30. Ohnuki K, Yoshida S, Ohta M et al. New diagnostic technique in multi-slice computed tomography for in-stent restenosis: Pixel count method. Int J Cardiol 2006; 108: 251–8. Cademartiri F, Runza G, La Grutta L et al. Noninvasive assessment of coronary artery stent patency with multislice CT: preliminary experience. Radiol Med 2005; 190: 500–7. Kitagawa T, Fujii T, Tomohiro Y et al. Noninvasive assessment of coronary stents in patients by 16-slice computed tomography. Int J Car-
diol 2006; 109: 188-94. 24. Maintz D, Seifarth H, Flohr T et al. Improved coronary artery stent visualization and in-stent stenosis detection using 16-slice computedtomography and dedicated image reconstruction technique. Invest Radiol 2003; 38: 790– 5. 25. Seifarth H, Raupach R, Schaller S et al. Assessment of coronary artery stents using 16-slice MDCT angiography: evaluation of a dedicated reconstruction kernel and a noise reduction filter. Eur Radiol 2005; 15:721–6. 26. Kefer JM, Coche E, Vanoverschelde JL, Gerber BL. Diagnostic accuracy of 16-slice multidetector-row CT for detection of in-stent restenosis vs detection of stenosis in nonstented coronary arteries. Eur Radiol 2007; 17: 87-96.
9
Comparison of 16-Slice Computed Tomography with Conventional Angiography to Evaluate Coronary Artery Stent Patency Koroner Arter Stentlerinde Patensinin Belirlenmesinde 16 Dedektörlü Bilgisayarlı Tomografi ile Konvansiyonel Anjiyografi Bulgularının Karşılaştırılması Irmak Durur-Subasi1, Mecit Kantarci2, Afak Durur-Karakaya2, Adnan Okur2 1
Yozgat State Hospital, Department of Radiology, Yozgat, Turkey Ataturk University, Faculty of Medicine, Department of Radiology, Erzurum, Turkey
2
Correspondence to: Dr. Irmak Durur-Subasi, Yozgat State Hospital, Department of Radiology, 66000 Yozgat, Turkey. Phone: +90.354.2171060-1181, Fax: +90.354.2126309, e-mail: [email protected]
Abstract
Özet
Objective. In this study, we evaluated the utility of 16-slice MDCT (multidetector computed tomography) to assess stent patency after coronary artery stenting.
Amaç. Bu çalışmada koroner arter stentlerinde 16 kesitli bilgisayarlı tomografinin (BT) stent içi lümeni değerlendirmedeki rolünü inceledik.
Materials and Methods. Retrospective ECG-gated CT-angiography using 16-slice MDCT was performed in 52 consecutive patients with coronary artery stents. Qualitative assessment of 61 coronary stent lumens by MDCT is reported, and the reasons preventing assessment were investigated.
Gereç ve Yöntem. Koroner arter stenti yerleştirilmiş sıralı 52 hasta (61 stent), retrospektif elektrokardiyografi (EKG) kapılı BT anjiyografi ile incelendi. Altmış bir stentin lümenlerinin çok kesitli bilgisayarlı tomografi (ÇKBT) ile değerlendirilebilirliği nitel olarak gözden geçirildi ve değerlendirilemez görüntülerin sebepleri araştırıldı.
Results. All non-assessable stents were non-assessable due to partial volume effects and metal artifacts. To evaluate instent restenosis, conventional coronary angiography was performed on the 54 assessable stents in 48 patients, and the results were compared with the MDCT results. Based on the results of the conventional coronary angiography, MDCT correctly detected four in-stent restenosis. Conclusion. Despite some limitations, 16-slice MDCT provides sufficient evaluations of some coronary stents, and can detect in-stent restenosis with high accuracy.
Keywords: Coronary artery stents, Lumen patency, MDCT
The Eurasian Journal of Medicine
Bulgular. Değerlendirilemez görüntülere kısmi hacim etkileri ve metal artefaktları neden olmuştu. Ayrıca stent içi restenoz açısından değerlendirilebilir görüntülere sahip 48 hastadaki 54 stent, konvansiyonel koroner anjiyografi ile tetkik edilerek sonuçlar karşılaştırıldı. Konvansiyonel koroner anjiyografi ile karşılaştırıldığında ÇKBT koroner anjiyografi 4 stentte stent içi restenozu doğru bir şekilde tanıyabilmişti. Sonuç. Bazı sınırlılıklarına rağmen 16 kesitli bilgisayarlı tomografi koroner arter stentlerinin incelenmesinde yeterince yararlı bir yöntemdir. ÇKBT değerlendirilebilir görüntüler elde edildiğinde konvansiyonel koroner anjiyografi ile karşılaştırılabilir düzeyde yüksek doğruluğa sahip sonuçlar verebilmektedir. Anahtar Kelimeler: Koroner arter stentleri, Lümen açıklığı, ÇKBT
4
Subasi et al.
Introduction
T
he development of multidetector computed tomography (MDCT) has enabled visualization of coronary arteries with acceptable temporal and spatial resolution. MDCT has recently been used to evaluate coronary arteries, coronary plaques and coronary bypass grafts [1–8]. In this study, we investigated the utility of 16-slice MDCT in coronary stent visualization, the possible drawbacks and the accuracy of diagnosing in-stent re-stenosis compared to conventional coronary angiography.
Fig. 1
_
An axial contrast-enhanced CT image shows a 2.5 mm stent in the proximal segment of the LAD. The lumen cannot be visualized for partial volume effects.
Fig. 1
Patients and Methods Fifty-two consecutive patients (20-77 years old, mean 52.8 years, 48 males) with coronary artery stents, who could hold their breath long enough, and had no cardiac arrhythmia, were evaluated via retrospective ECG-gated CTangiography using 16-slice MDCT. Sixty-one (61) total stents were assessed. Patients with arrhythmia, renal insufficiency, intravenous contrast allergy, poor general health status, an inability to hold their breath for an extended period, x-ray contraindication, inability to cooperate during the scan, or a heart rate greater than 90 beats per minute were excluded from the study. Examinations were performed with a 16-slice scanner (Aquillon, Toshiba Medical Systems; Tokyo, Japan) during one breath-hold with the following parameters: 16 x 0.5 mm collimation, 1.0 mm detector thickness and 1.0 mm reconstruction interval. After acquisition, images were reconstructed with an R-R interval between 50% and 90% in 5% increments and were transferred to a workstation (Vitrea2, Vital Images; Minneapolis, MN, USA) for image analysis In addition to axial resource images, multiplanar reconstructions, curved multiplanar reformations, maximum intensity projection (MIP) images and 3D images were investigated for patency and re-stenosis. Two radiologists deemed the images sufficient or insufficient for each stent with regards to luminal patency and in-stent re-stenosis. If the lumen could be seen and was free of metal, motion or calcium artifacts, the images was accepted as sufficient. The reasons for insuffi-
EAJM: 41, April 2009
Fig. 2
_ Anterior view
of 3D volume rendering images shows a 3 mm stent in the middle segment of the RCA. The lumen cannot be visualized due to motion artifacts.
Fig. 2
cient images were examined. When vessel segments distal to the stent implantation region did not enhance, occlusion was diagnosed. Significant low density in the stent implantation region indicated in-stent re-stenosis. On the other hand, a homogenous intraluminal contrast density with similar contrast density to reference regions (e.g., proximal or distal of stent) indicated stent patency. Conventional angiography was performed by an interventional cardiologist with at least five years of experience who had no information about the MDCT angiography results. Stents with sufficient data from the MDCT angiography were also evaluated by conventional angiography for luminal patency and possible re-stenosis. The results of both modalities were compared. MDCT angiography and conventional angiography were performed within three days of each other.
5
Coronary Artery Stents Imaging with MDCT
A Fig. 3
B
C
_ 3.5 x 18.5 mm stent in the proximal segment of the LAD. In axial oblique MIP (A), vessel probe (B) and conventional angiography (C) images, luminal
patency is seen.
Results
angiography. MDCT correctly determined the luminal patency of the remaining 50 stents.
Fifty-two (52) consecutive patients (20-77 years old, mean 52.8 years, 48 male) with coronary artery stents underwent MDCT coronary angiography in our department with no complications. In total, 61 stents were evaluated; 54 of the stents (88.5%) were found to be sufficient, and 7 (11.5%) were insufficient. Reasons for insufficient imaging included motion artifacts, partial volume effects and metal artifacts. Based on caliber, stents wider than 3.5 mm had a higher rate of sufficient imaging (43/45, 95.5%). Three (3.0)-millimeter stents had a lower rate of sufficient imaging secondary to metal and motion artifacts (11/14, 78.6%). Notably, 2.5-mm stents (two stents) were not evaluated for metal artifacts and partial volume effects (Table 1) (Figures 1-7).
Discussion Coronary artery disease has been increasingly treated with percutaneous angioplasty and intracoronary stent placement. Although stent deployment significantly reduces the re-stenosis rate when compared to balloon angioplasty, 30% of cases may have neointimal proliferation, which leads to restenosis [9–12]. Conventional angiography is the gold standard for detecting re-stenosis. Although it is an effective diagnostic tool, it is associated with significant morbidity (1.7%) and mortality (0.11%). Moreover, it is an invasive method that requires hospitalization [13].
Forty-eight (48) patients with 54 stents assessable by MDCT coronary angiography underwent conventional angiography. Four cases exhibited in-stent re-stenosis, which were observed via conventional angiography and MDCT coronary
Thus, several other methods have been evaluated to identify in-stent re-stenosis. However, neither magnetic resonance imaging nor electron beam tomography has provided sufficient imaging of the lumen [14,15]. With MDCT, iliac and
A Fig. 4
B
C
_ Two stents (3.5 mm) in the proximal and middle segments of the LAD. Axial oblique MIP (A), vessel probe (B) and conventional angiography (C)
images show the luminal patency.
EAJM: 41, April 2009
6
Subasi et al.
Fig. 5 A
Krüger et al. studied 20 patients with coronary stents using four-slice computed tomography and reported that the stent lumens could not be visualized [18]. In another study using four-slice CT, Maintz et al. reported that 58% of the stents were assessable, and they calculated 100% sensitivity and 50% specificity in defining in-stent re-stenosis [19]. Schuijf et al. studied 22 patients with 16-slice MDCT, and they found 77% of the stents were assessable, with 78% sensitivity and 100% specificity for detecting in-stent re-stenosis [20]. Ohnuki et al. reported 95% of stents were assessable with 75% sensitivity and 88% specificity with this technique [21]. Similarly, Cademartiri et al. reported that all stents in 51 patients were assessable, and they calculated 69% sensitivity and 95% specificity [22], while Gilarda et al. studied 143 patients, and observed that 64% of the stents were assessable with 54% sensitivity and 100% specificity. In our study, we
A Fig. 6
ment of the LAD. Axial oblique MIP (A) and 3D volume rendering (B) images show luminal patency.
B
carotid stent lumens, and even neointimal hyperplasia, have been shown [16,17]. For smaller vessels (e.g., coronary or cerebral arteries) imaging of the lumen, neointimal hyperplasia or in-stent re-stenosis is more challenging.
B
_ 3.5 x 22 mm stent in the middle seg-
were able to assess 88.5% of the stents, and four stents with re-stenosis were also confirmed by conventional angiography. In our study, there was a connection between the level of stent metal artifacts and stent caliber. Metal in the stent strut absorbs x-ray and leads to beam hardening and high-density artifacts. This false narrowing causes misinterpretation. Tantalum has been reported to have more metal artifacts and therefore should not be evaluated with MDCT [23]. In addition, stents with gold markers (e.g., Bestent2) were reported to be poorly evaluated in this study, and thicker stent struts increased the incidence of metal artifacts in the same study [24,25]. For 3 mm or smaller caliber stents, partial volume effects and metal artifacts poisoned the luminal image, and 2.5 mm caliber stents cannot be imaged by 16-slice CT at all. Heart motion artifacts and severe calcifications prevented stent imaging. Heart motion artifacts especially influence stents located in right coronary artery (RCA) (chiefly segment 2). Calcifications in the proximal portion of the left anterior
C
_
3.5 x 16 mm and a 4 x 9 mm stent in the middle segment of the left circumflex (LCx). Coronal oblique MIP (A), 3D volume rendering (B) and vessel probe (C) images show the patent stent.
EAJM: 41, April 2009
7
Coronary Artery Stents Imaging with MDCT
_
Fig. 7 3.5 x 16 mm stent in the proximal portion of an aorta (Ao)-LCx free saphenous graft. Axial oblique MIP (A) and 3D volume rendering (B) images show the patent stent.
A
B
descending artery (LAD) are potentially more dense and affect stents located in segment 6. In our study, we showed that, in four assessable stents, MDCT determined in-stent re-stenosis with 100% accuracy, as confirmed via conventional angiography. Detecting restenosis after stent deployment is of great clinical importance, as re-stenosis may develop in up to 46% of stents within the first 6 months [26]. When a patient presents to a physician with angina after stent deployment, invasive conventional angiography may be needed. As the population who undergoes
coronary artery stenting increases, non-invasive imaging of the luminal patency in these patients is needed. With its high specificity and negative predictive value, MDCT coronary angiography should enter into routine clinical practice, thereby preventing unnecessary cardiac catheterization. Conventional angiography with high spatial resolution is the gold standard for imaging coronary arteries, but it cannot show the vessel wall. MDCT coronary angiography will thus play an important role in future coronary artery stent imaging with its high spatial resolution and rapid acquisition.
Conflict interest statement The authors declare that they have no conflict of interest to the publication of this article.
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