Usefulness of 64-slice multislice computed tomography coronary angiography to assess in-stent restenosis

Enhancing diagnostic performance and image quality in coronary CT angiography: Impact of SnapShot Freeze 2 algorithm across varied heart rates in stent patients

PURPOSE

To investigate the enhancement of image quality achieved through the utilization of SnapShot Freeze 2 (SSF2), a comparison was made against the results obtained from the original SnapShot Freeze algorithm (SSF) and standard motion correction (STND) in stent patients undergoing coronary CT angiography (CCTA) across the entire range of heart rates.

MATERIALS AND METHODS

A total of 118 patients who underwent CCTA, were retrospectively included in this study. Images of these patients were reconstructed using three different algorithms: SSF2, SSF, and STND. Objective assessments include signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), diameters of stents and artifact index (AI). The image quality was subjectively evaluated by two readers.

RESULTS

Compared with SSF and STND, SSF2 had similar or even higher quality in the parameters (AI, SNR, CNR, inner diameters) of coronary artery, stent, myocardium, MV (mitral valve), TV (tricuspid valve), AV (aorta valve), and PV (pulmonary valve), and aortic root (AO). Besides the above structures, SSF2 also demonstrated comparable or even higher subjective scores in atrial septum (AS), ventricular septum (VS), and pulmonary artery root (PA). Furthermore, the enhancement in image quality with SSF2 was significantly greater in the high heart rate group compared to the low heart rate group. Moreover, the improvement in both high and low heart rate groups was better in the SSF2 group compared to the SSF and STND group. Besides, when using the three algorithms, an effect of heart rate variability on stent image quality was not detected.

CONCLUSION

Compared to SSF and STND, SSF2 can enhance the image quality of whole-heart structures and mitigate artifacts of coronary stents. Furthermore, SSF2 has demonstrated a significant improvement in the image quality for patients with a heart rate equal to or higher than 85 bpm.

Standards for quantitative assessments by coronary computed tomography angiography (CCTA): An expert consensus document of the society of cardiovascular computed tomography (SCCT)

In current clinical practice, qualitative or semi-quantitative measures are primarily used to report coronary artery disease on cardiac CT. With advancements in cardiac CT technology and automated post-processing tools, quantitative measures of coronary disease severity have become more broadly available. Quantitative coronary CT angiography has great potential value for clinical management of patients, but also for research. This document aims to provide definitions and standards for the performance and reporting of quantitative measures of coronary artery disease by cardiac CT.

Appropriateness criteria for the use of cardiac computed tomography, SIC-SIRM part 2: acute chest pain evaluation; stent and coronary artery bypass graft patency evaluation; planning of coronary revascularization and transcatheter valve procedures; cardiomyopathies, electrophysiological applications, cardiac masses, cardio-oncology and pericardial diseases evaluation

In the past 20 years, cardiac computed tomography (CCT) has become a pivotal technique for the noninvasive diagnostic workup of coronary and cardiac diseases. Continuous technical and methodological improvements, combined with fast growing scientific evidence, have progressively expanded the clinical role of CCT. Randomized clinical trials documented the value of CCT in increasing the cost-effectiveness of the management of patients with acute chest pain presenting in the emergency department, also during the pandemic. Beyond the evaluation of stents and surgical graft patency, the anatomical and functional coronary imaging have the potential to guide treatment decision-making and planning for complex left main and three-vessel coronary disease. Furthermore, there has been an increasing demand to use CCT for preinterventional planning in minimally invasive procedures, such as transcatheter valve implantation and mitral valve repair. Yet, the use of CCT as a roadmap for tailored electrophysiological procedures has gained increasing importance to assure maximum success. In the meantime, innovations and advanced postprocessing tools have generated new potential applications of CCT from the simple coronary anatomy to the complete assessment of structural, functional and pathophysiological biomarkers of cardiac disease. In this complex and revolutionary scenario, it is urgently needed to provide an updated guide for the appropriate use of CCT in different clinical settings. This manuscript, endorsed by the Italian Society of Cardiology (SIC) and the Italian Society of Medical and Interventional Radiology (SIRM), represents the second of two consensus documents collecting the expert opinion of cardiologists and radiologists about current appropriate use of CCT.

Coronary CT angiography: a guide to examination, interpretation, and clinical indications

INTRODUCTION

The introduction of Cardiac Computed Tomography (CCT) has changed the paradigm in the field of diagnostic cardiovascular medicine. CCT is the primary tool in the assessment of suspected Coronary Artery Disease (CAD) and should be followed by functional assessment when needed to stratify disease and to plan potential interventional or surgical therapy.

AREAS COVERED

We provided the current state of the knowledge on the main aspects of technique of examination, image interpretation and clinical indications. We have focused our attention on the basic routine applications and activities.

EXPERT OPINION

The primary role of CCT in suspected CAD will progressively become the standard approach. In general, any situation in which anatomy of the heart and thoracic vessels/structures is mandatory must be approached using CT first, whenever possible. The quantity and quality of information that can be provided by CCT is big and the operators should learn how to deal with this information. On the other hand, CCT is only apparently a straightforward and simple examination. It is actually the most complex diagnostic procedure that can be performed on CT and requires highly skilled operators and state-of-art-technology.

Coronary atherosclerosis as the main endpoint of non-invasive imaging in cardiology: a narrative review

The change of paradigm determined by the introduction of cardiac computed tomography (CCT) in the field of cardiovascular medicine has allowed new evidence to emerge. These evidences point towards a major role, probably the most important one in terms of prognostic impact, in the detection, characterization and quantification of atherosclerosis as the main driver and endpoint for the management of coronary artery disease (CAD). Extensive literature has been published in the last decade with large numbers and patients' populations, investigating several aspects and correlations between atherosclerotic plaque features and risk factors; also, the relationship between plaque features, both with qualitative and quantitative approaches, and cardiovascular events has been investigated. More recent studies have also pointed out the relationship between the knowledge and classification of sub-clinical atherosclerosis and the induced modification of medical therapy (both aggressiveness and compliance) that is most likely able to increase the effect of anti-atherosclerotic drugs, hence significantly improving prognosis. Non-invasive assessment of CAD by means of CCT is becoming the primary tool for management and also the most important parameter for the comprehension of natural history of CAD and how the therapies we adopt are affecting plaque burden as a whole. In this review we will address the modern concepts of CAD driven understanding and management of cardiovascular disease.

Diagnostic performance of two corrected transluminal attenuation gradient metrics in coronary CT angiography for the evaluation of significant in-stent restenosis by dual-source CT: a validation study with invasive coronary angiography

AIM

To determine the diagnostic potential of transluminal attenuation gradients (TAG) with exclusion of stented coronary segments (TAG-ExS) and TAG-corrected contrast opacification (CCO) excluding stented coronary segments (TAG-CCO-ExS) for the assessment of in-stent restenosis (ISR).

MATERIALS AND METHODS

TAG-ExS and TAG-CCO-ExS were calculated in 93 coronary arteries with 190 stents. The diagnostic performances and the incremental values of the two metrics to coronary computed tomography angiography (CCTA) were analysed and compared.

RESULTS

For all stents and stents >3 mm in diameter, TAG-ExS and TAG-CCO-ExS were significantly lower in ≥50% than that in <50% of ISR (both p<0.05). For stent diameters ≤3 mm, significantly lower TAG-CCO-ExS (p=0.000), but not TAG-ExS (p=0.059), was found in ≥50% than in <50% of ISR. Addition of TAG-ExS or TAG-CCO-ExS to CCTA, did not improve the diagnostic accuracy of CCTA significantly (all p>0.05). Only TAG-CCO-ExS had a significant impact on CCTA for the reclassifications of ISR (p=0.046) in stent diameters ≤3 mm.

CONCLUSIONS

TAG-ExS and TAG-CCO-ExS did not provide incremental diagnostic value over CCTA in assessing ISR. TAG-CCO-ExS slightly enhanced the reclassifications of ISR for stents ≤3 mm in diameter.

Diagnostic accuracy of in-stent restenosis using model-based iterative reconstruction at coronary CT angiography: initial experience

OBJECTIVE

The purpose of our study was to compare the diagnostic performance of coronary CT angiography (CTA) subjected to model-based iterative reconstruction (IR) or hybrid IR to rule out coronary in-stent restenosis.

METHODS

We enrolled 16 patients who harboured 22 coronary stents. They underwent coronary CTA on a 320-slice CT scanner. The images were reconstructed with hybrid IR (AIDR 3D) and model-based IR (FIRST) algorithms. We calculated the stent lumen attenuation increase ratio and measured the visible stent lumen diameter. Two blinded observers visually graded the likelihood of in-stent restenosis (lesions ≥ 50%) on hybrid IR and FIRST images.

RESULTS

The stent lumen attenuation increase ratio on FIRST- was lower than on AIDR 3D images (0.20 vs 0.32). The ratio of the visible- compared to the true stent lumen diameter was higher on FIRST- than AIDR 3D images (52.5 vs 47.5%). Invasive coronary angiography identified five stents (22.7%) with significant in-stent restenosis. The use of FIRST improved the sensitivity (60 vs 100%), positive (75.0 vs 83.3%) and negative predictive value (88.9 vs 100%) and the accuracy (86.4 vs 95.5%) for the detection of in-stent restenosis. Specificity was 94.1% for both reconstruction methods.

CONCLUSION

The model-based IR algorithm may improve diagnostic performance for the detection of in-stent restenosis. Advances in knowledge: Compared to hybrid IR, the new model-based IR algorithm reduced blooming artefacts and improved the image quality. It can be expected to improve diagnostic performance for the detection of in-stent restenosis on coronary CTA images.

Coronary Artery Stent Evaluation with Model-based Iterative Reconstruction at Coronary CT Angiography

RATIONALE AND OBJECTIVES

This study aims to compare the image quality of coronary artery stent scans on computed tomography images reconstructed with forward projected model-based iterative reconstruction solution (FIRST) and adaptive iterative dose reduction 3D (AIDR 3D).

MATERIALS AND METHODS

Coronary computed tomography angiography scans of 23 patients with 32 coronary stents were used. The images were reconstructed with AIDR 3D and FIRST. We generated computed tomography attenuation profiles across the stents and measured the width of the edge rise distance and the edge rise slope (ERS). We also calculated the stent lumen attenuation increase ratio (SAIR) and measured visible stent lumen diameters. Two radiologists visually evaluated the image quality of the stents using a 4-point scale (1 = poor, 4 = excellent).

RESULTS

There was no significant difference in the edge rise distance between the two reconstruction methods (P = 0.36). The ERS on FIRST images was greater than the ERS on AIDR 3D images (325.2 HU/mm vs 224.4 HU/mm; P <0.01). The rate of the visible stent lumen diameter compared to the true diameter on FIRST images was higher than that on AIDR 3D images (51.4% vs 47.3%, P <0.01). The SAIR on FIRST images was lower than the SAIR on AIDR 3D images (0.19 vs 0.30, P <0.01). The mean image quality scores for AIDR 3D and FIRST images were 3.18 and 3.63, respectively; the difference was also significant (P <0.01).

CONCLUSION

The image quality of coronary artery stent scans is better on FIRST than on AIDR 3D images.

Coronary Stent Artifact Reduction with an Edge-Enhancing Reconstruction Kernel - A Prospective Cross-Sectional Study with 256-Slice CT

Purpose

Metallic artifacts can result in an artificial thickening of the coronary stent wall which can significantly impair computed tomography (CT) imaging in patients with coronary stents. The objective of this study is to assess in vivo visualization of coronary stent wall and lumen with an edge-enhancing CT reconstruction kernel, as compared to a standard kernel.

Methods

This is a prospective cross-sectional study involving the assessment of 71 coronary stents (24 patients), with blinded observers. After 256-slice CT angiography, image reconstruction was done with medium-smooth and edge-enhancing kernels. Stent wall thickness was measured with both orthogonal and circumference methods, averaging thickness from diameter and circumference measurements, respectively. Image quality was assessed quantitatively using objective parameters (noise, signal to noise (SNR) and contrast to noise (CNR) ratios), as well as visually using a 5-point Likert scale.

Results

Stent wall thickness was decreased with the edge-enhancing kernel in comparison to the standard kernel, either with the orthogonal (0.97 ± 0.02 versus 1.09 ± 0.03 mm, respectively; p<0.001) or the circumference method (1.13 ± 0.02 versus 1.21 ± 0.02 mm, respectively; p = 0.001). The edge-enhancing kernel generated less overestimation from nominal thickness compared to the standard kernel, both with the orthogonal (0.89 ± 0.19 versus 1.00 ± 0.26 mm, respectively; p<0.001) and the circumference (1.06 ± 0.26 versus 1.13 ± 0.31 mm, respectively; p = 0.005) methods. The edge-enhancing kernel was associated with lower SNR and CNR, as well as higher background noise (all p < 0.001), in comparison to the medium-smooth kernel. Stent visual scores were higher with the edge-enhancing kernel (p<0.001).

Conclusion

In vivo 256-slice CT assessment of coronary stents shows that the edge-enhancing CT reconstruction kernel generates thinner stent walls, less overestimation from nominal thickness, and better image quality scores than the standard kernel.

[Coronary stent evaluation with cardiac CT: Literature review]

Since the introduction of the 64-generation scanners, the accuracy and robustness of the diagnosis of coronary artery disease has progressed. The main advantage of cardiac CT is the exclusion of coronary artery disease by its excellent negative predictive value. Currently, cardiac CT applications extend thanks to innovations both in terms of technological development systems scanner or stents implanted. This is a literature review of stent evaluation with cardiac CT.

[Cardiac CT: new applications]

Since the introduction of the 64-generation scanners, the accuracy and robustness of the diagnosis of coronary artery disease has progressed. The main advantage of cardiac CT is the exclusion of coronary artery disease by its excellent negative predictive value. Currently, cardiac CT applications extend thanks to innovations both in terms of technological development systems scanner or stents implanted, that the evolution of surgical procedures such as TAVI.

Coronary stent occlusion: reverse attenuation gradient sign observed at computed tomography angiography improves diagnostic performance

OBJECTIVES

To evaluate the incidence and diagnostic performance of reverse attenuation gradient (RAG) sign in patients with coronary stent occlusion.

METHODS

We retrospectively included patients with suspected restenosis who underwent both coronary computed tomography angiography (CCTA) and invasive coronary angiography (ICA) within 2 weeks. Stent occlusion at CCTA was defined as (1) complete contrast filling defect of large calibre stents (at least 3 mm), or (2) presence of RAG sign in patients with small calibre stents (less than 3 mm) or (3) presence of RAG sign in patients with non-diagnostic image quality of stents. The diagnostic performance of RAG sign was further assessed by comparison to ICA results.

RESULTS

A total of 162 patients with 231 implanted stents were included. ICA confirmed stent occlusion in 59 patients (99 stents). RAG sign was present in 59.3% (35/59) of all stent occlusions. As shown by patient-based analysis, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of our diagnostic criteria for detection of stent occlusion were 79.7% (47/59), 100% (103/103), 100% (47/47) and 89.6% (103/115) respectively. Superior diagnostic performance was confirmed by receiver operating characteristic (ROC) analysis with an area under the curve of 0.898.

CONCLUSIONS

RAG sign observed at CCTA in patients with coronary stenting represents reverse collateral flow distal to stents and is highly specific to indicate stent occlusion.

KEY POINTS

• RAG sign in patients with previous stents represents retrograde collateral flow. • RAG sign in patients with previous stents indicates stent occlusion. • RAG sign improves detection of stent occlusion in small calibre stents.

The utility of the combination of the corrosion cast method and post mortem MSCT scans

A careful post-mortem investigation is needed to determine the cause of death of patients bearing coronary stents and to describe complications of stent implantation. The main purpose of this study was to combine post mortem methods of CT angiography and corrosion cast preparation for the visualization of coronary stenoses, coronary stents, instent restenosis, and stent occlusion. Injection-corrosion method was combined with post-mortem MSCT angiography to characterize the pathomorphological changes after stent implantation in 6 male cadaver hearts. Multi-slice computed tomography was employed to visualize the coronary artery system. For image post processing, multiplanar reconstructions, maximal intensity projections and three dimensional reconstructions were used. This study was assessing the feasibility of post mortem MSCT for intracoronary stent evaluation. We described a method for characterization of the coronary side branch stenosis caused by stent implantation. Post mortem CT imaging proved to be a feasible and highly reproducible technique for the characterization of pathological changes in the coronary system.

[Examination of the effectiveness of heart rate control using intravenous β-blocker in 64-slice coronary computed tomography angiography]

The purpose of this study is to clarify the effectiveness of the use of β-blocker in coronary computed tomography angiography (CCTA). In 1783 patients, heart rate was controlled by propranolol injection to patients with heart rates of 61 bpm or more. As a result, the scan heart rate (58.8±6.5 bpm) decreased significantly compared with the initial heart rate (72.7±9.4 bpm). Prospective gating method was used by 61.9% including 64.3% of the intravenous β-blocker injection group. Moreover, daily use of oral β-blocker had influence on reduction of the scan heart rate (daily use group: 60.1±6.5 bpm vs. unuse group: 58.5±6.3 bpm p<0.01). When we evaluated the image quality of CCTA by the score, the improvement of the score was obviously admitted by 65 bpm or less of the scan heart rate. The ratio of scan heart rate that was controlled by 65 bpm or less was decreased in the initial heart rate groups that were 81 bpm or more. The incidence of adverse reactions by the propranolol injection was few, and these instances only involved slight symptoms. Therefore, heart rate control with the use of β-blocker is useful for the image quality improvement of CCTA. This form of treatment can be safely enforced.

CT Imaging of Coronary Stents: Past, Present, and Future

Coronary stenting became a mainstay in coronary revascularization therapy. Despite tremendous advances in therapy, in-stent restenosis (ISR) remains a key problem after coronary stenting. Coronary CT angiography evolved as a valuable tool in the diagnostic workup of patients after coronary revascularization therapy. It has a negative predictive value in the range of 98% for ruling out significant ISR. As CT imaging of coronary stents depends on patient and stent characteristics, patient selection is crucial for success. Ideal candidates have stents with a diameter of 3 mm and more. Nevertheless, even with most recent CT scanners, about 8% of stents are not accessible mostly due to blooming or motion artifacts. While the diagnosis of ISR is currently based on the visual assessment of the stent lumen, functional information on the hemodynamic significance of in-stent stenosis became available with the most recent generation of dual source CT scanners. This paper provides a comprehensive overview on previous developments, current techniques, and clinical evidence for cardiac CT in patients with coronary artery stents.

Coronary in-stent restenosis: assessment with CT coronary angiography

PURPOSE

To compare accuracy and radiation exposure of a new computed tomographic (CT) scanner with improved spatial resolution (scanner A) with those of a CT scanner with standard spatial resolution (scanner B) for evaluation of coronary in-stent restenosis (ISR) by using invasive coronary angiography (ICA) and intravascular ultrasonography (US) as reference methods.

MATERIALS AND METHODS

Written informed consent was obtained and study protocol was approved by institutional ethics committee. A total of 180 consecutive patients (154 men [mean age ± standard deviation, 66 years±12; range, 51-79 years] and 36 women [mean age, 70 years±12; range, 55-83 years]) scheduled to undergo ICA for suspected ISR were enrolled. Ninety patients were studied with scanner A (group 1: 72 men [mean age, 65 years±11; range, 52-79], 18 women [mean age, 68 years±12; range, 55-83 years]) and 90 with scanner B (group 2: 74 men [mean age, 64 years±10; range, 51-77 years], 16 women [mean age, 68 years±11; range, 55-82 years). Examination with the two scanners was compared with ICA and intravascular US. Radiation dose exposure was estimated. To compare stent evaluability between the two groups, χ2 test was used.

RESULTS

Stent evaluability was higher in group 1 than in group 2 (99% vs 92%, P=.0021). A significantly lower rate of beam-hardening artifact was observed in group 1 (two cases) than group 2 (12 cases, P<.05). For stent-based analysis, sensitivity, specificity, and accuracy of multidetector CT for ISR identification were 96%, 95%, and 96% in group 1 and 90%, 91%, and 91% in group 2, respectively, without statistically significant differences. The correlation between percent ISR evaluated at multidetector CT versus intravascular US was higher in group 1 than in group 2 (r=0.89 vs r=0.58; P=.019). The correlations of diameter and area measurements at reference site and stent maximal lumen narrowing site between multidetector CT and intravascular US were higher in group 1 than in group 2. Radiation dose was low in both multidetector CT groups (1.9 mSv±0.2).

CONCLUSION

Scanner A, with improved spatial resolution, allowed reliable detection and quantification of coronary ISR with low radiation exposure.

Clinical indications for cardiac computed tomography. From the Working Group of the Cardiac Radiology Section of the Italian Society of Medical Radiology (SIRM)

Cardiac computed tomography (CCT) has grown as a useful means in different clinical contexts. Technological development has progressively extended the indications for CCT while reducing the required radiation dose. Even today there is little documentation from the main international scientific societies describing the proper use and clinical indications of CCT; in particular, there are no complete guidelines. This document reflects the position of the Working Group of the Cardiac Radiology Section of the Italian Society of Radiology concerning the indications for CCT.

High-definition computed tomography for coronary artery stent imaging: a phantom study

Objective

To assess the performance of a high-definition CT (HDCT) for imaging small caliber coronary stents (≤ 3 mm) by comparing different scan modes of a conventional 64-row standard-definition CT (SDCT).

Materials and Methods

A cardiac phantom with twelve stents (2.5 mm and 3.0 mm in diameter) was scanned by HDCT and SDCT. The scan modes were retrospective electrocardiography (ECG)-gated helical and prospective ECG-triggered axial with tube voltages of 120 kVp and 100 kVp, respectively. The inner stent diameters (ISD) and the in-stent attenuation value (AV_in-stent) and the in-vessel extra-stent attenuation value (AV_in-vessel) were measured by two observers. The artificial lumen narrowing (ALN = [ISD - ISD_measured]/ISD) and artificial attenuation increase between in-stent and in-vessel (AAI = AV_in-stent - AV_in-vessel) were calculated. All data was analyzed by intraclass correlation and ANOVA-test.

Results

The correlation coefficient of ISD, AV_in-vessel and AV_in-stent between the two observers was good. The ALNs of HDCT were statistically lower than that of SDCT (30 ± 5.7% versus 35 ± 5.4%, p < 0.05). HDCT had statistically lower AAI values than SDCT (15.7 ± 81.4 HU versus 71.4 ± 90.5 HU, p < 0.05). The prospective axial dataset demonstrated smaller ALN than the retrospective helical dataset on both HDCT and SDCT (p < 0.05). Additionally, there were no differences in ALN between the 120 kVp and 100 kVp tube voltages on HDCT (p = 0.05).

Conclusion

High-definition CT helps improve measurement accuracy for imaging coronary stents compared to SDCT. HDCT with 100 kVp and the prospective ECG-triggered axial technique, with a lower radiation dose than 120 kVp application, may be advantageous in evaluating coronary stents with smaller calibers (≤ 3 mm).

Comparison between different kernel reformatting filters in 3D quantitative analysis of MDCT coronary angiography

PURPOSE

Coronary angiography with multidetector-row computed tomography (MDCT-CA) allows quantification of coronary artery stenosis with a high level of accuracy; however, a better estimation of stenosis can be achieved by using appropriate reformatting filters, especially in stents and calcified segments. Quantitative computed tomography angiography (QCTA) is intended to overcome the limitations of the visual score. The aim of this study was to evaluate the accuracy of QCTA with different filters in comparison with quantitative coronary angiography (QCA) and visual score.

MATERIALS AND METHODS

Two blinded operators visually scored 17 consecutive patients referred for MDCT-CA with a per-segment analysis. The degree of stenosis was classified as 0-20%, 20-50% (wall irregularities), 50-70% (significant disease) and 70-100% (vessel occlusion). Each segment was then analysed using the electronic callipers of the QCTA system with 15 different filters. No contour editing was performed. Data were compared with QCA and conventional coronary angiography (CCA). Comparison between QCTA, visual score and QCA were performed using Spearman's rank correlation.

RESULTS

Of 25 segments analysed (mean 1.4 diseased segment per patient), 375 measurements were considered. Good correlation was found between the visual score and QCA [Pearson correlation coefficient (rho=0.852; p<0.0001)] and between QCA and CCA (rho=0.804; p<0.0001). Moderate correlation was found between QCA and QCTA only using two filters (rho=0.444; p<0.0001 for YA filter and rho=0.450; p<0.0001 for YB filter).

CONCLUSIONS

Overall QCTA accuracy is low if contour editing is not applied, especially in calcified vessels. Certain filters can help to better estimate the exact percentage of stenosis.

Cardiac multidetector computed tomography: basic physics of image acquisition and clinical applications

Cardiac MDCT is here to stay. And, it is more than just imaging coronary arteries. Understanding the differences in and the benefits of one CT scanner from another will help you to optimize the capabilities of the scanner, but requires a basic understanding of the MDCT imaging physics.

This review provides key information needed to understand the differences in the types of MDCT scanners, from 64 – 320 detectors, flat panels, single and dual source configurations, step and shoot prospective and retrospective gating, and how each factor influences radiation dose, spatial and temporal resolution, and image noise.

In vivo evaluation of stent patency by 64-slice multidetector CT coronary angiography: shall we do it or not?

The diagnostic performance of in-stent restenosis (ISR) by 64-slice multidetector CT coronary angiography (CTCA) has been reported to be influenced by multiple factors. We evaluated individual factors (stent diameter, material and strut thickness) and therefore determined the proper population for follow-up by using this modality. A total of 171 stents were evaluated in 83 consecutive patients with stents imaged with CTCA and conventional coronary angiography. The stent diameter ranged from 2.25 mm to 4.5 mm. 2 models of stainless steel (Taxus Liberte (Boston Scientific, US), 56 stents and Cypher Select (Cordis, US), 34 stents) and 2 models of cobalt alloy (Endeavor (Medtronic, US), 33 stents and Firebird2 (MicroPort, China), 48 stents) were included. By comparing to conventional coronary angiography, the image quality and diagnostic accuracy for ISR were evaluated. The image quality of Taxus, Endeavor and Firebird are markedly better than Cypher in large caliber group (≧3.0 mm) (P < 0.001). Except for Cypher, all other stents with diameter ≧3.0 mm showed excellent diagnostic accuracy (sensitivity 100%, specificity 94.4-96% whereas stents with diameter <3.0 mm had poor diagnostic accuracy (sensitivity 100%, specificity 33.3-70%). Cypher is the stent with thickest strut in our study, and showed reduced image quality and diagnostic accuracy in all stent size, due to large number of unassessable stents. Among 16 binary ISR, 12 lesions were correctly diagnosed by CTCA while the other 4 lesions were unassessable. The main reason for low specificity in small caliber group is the large number of unassessable stents. CTCA has high diagnostic accuracy to identify ISR in selected stents with a diameter of ≧3.0 mm.

In vivo assessment of coronary stents with 64-row multidetector computed tomography: analysis of metal artifacts

OBJECTIVE

To evaluate stent-induced artifacts by 64-row multidetector computed tomography (MDCT).

METHODS

We studied 26 stented patients with MDCT before conventional coronary angiography (CCA). The CT values were measured. Stents were classified as occluded, with significant stenosis, with nonsignificant stenosis, or patent. For the patent stents, mean in-stent and out-stent CT values were compared; stents 3 mm or smaller were compared with stents larger than 3 mm. Multidetector CT was compared with CCA.

RESULTS

We analyzed 42 stents. At CCA, 34 stents were patent, 5 were nonsignificantly stenosed, 1 was significantly stenosed, and 2 were occluded. At MDCT, 33 of 34 patent stents, 2 occluded stents, and 1 stent with significant stenosis were correctly diagnosed; nonsignificant stenoses were undetected, 1 patent stent was misdiagnosed as occluded (κ = 0.727). The out-stent CT value was lower than in-stent CT value both in stents 3 mm or smaller (P = 0.001) and stents larger than 3 mm (P < 0.001). The in-stent CT value of stents 3 mm or smaller was higher (P = 0.011) than that of stents larger than 3 mm.

CONCLUSIONS

Metal artifacts cause overlooking of nonsignificant stenosis.

Preoperative cardiac risk management

Approximately 100 million people undergo noncardiac surgery annually worldwide. It is estimated that around 3% of patients undergoing noncardiac surgery experience a major adverse cardiac event. Although cardiac events, like myocardial infarction, are major cause of perioperative morbidity or mortality, its true incidence is difficult to assess. The risk of perioperative cardiac complications depends mainly on two conditions: (1) identified risk factors, and (2) the type of the surgical procedure. On that basis, different scoring systems have been developed in order to accurately assess the perioperative cardiac risk and to improve the patient management. Importantly, patients with estimated high risk should be tested preoperatively by non-invasive cardiac imaging modalities. According to test results, they can proceed directly to planed surgery with the use of cardioprotective drugs (beta-blockers, statins, aspirin), or to myocardial revascularization prior to non-cardiac surgery. In this review, we discuss the role of clinical cardiac risk factors, laboratory measurements, additional non-invasive cardiac testing, and consequent strategies in perioperative management of patients undergoing noncardiac surgery.

Coming of age: coronary computed tomography angiography

Technical development has substantially improved diagnostic performance of coronary computed tomography angiography (CCTA). A large number of studies have addressed proof of concept, feasibility, and clinical robustness of this noninvasive diagnostic technique, and most have consistently described the ability of CCTA to reliably rule out significant coronary artery stenosis. Clinical evidence supports the significant role of CCTA in an increasing number of scenarios, including the detection of coronary disease in symptomatic patients who are at intermediate risk and evaluation of coronary revascularization procedures. After initial feasibility testing, the scientific evaluation of CCTA now points toward analyzing prognosis, outcome, and cost-effectiveness of this noninvasive diagnostic tool. In this article, appropriate clinical indications, diagnostic performance, current clinical applications, prognostic value, and cost-effectiveness of CCTA are reviewed.

Evaluation of the second generation of a bioresorbable everolimus drug-eluting vascular scaffold for treatment of de novo coronary artery stenosis: six-month clinical and imaging outcomes

BACKGROUND

The first generation of the bioresorbable everolimus drug-eluting vascular scaffold showed signs of shrinkage at 6 months, which largely contributed to late luminal loss. Nevertheless, late luminal loss was less than that observed with bare metal stents. To maintain the mechanical integrity of the device up to 6 months, the scaffold design and manufacturing process of its polymer were modified.

METHODS AND RESULTS

Quantitative coronary angiography, intravascular ultrasound with analysis of radiofrequency backscattering, and as an optional assessment, optical coherence tomography (OCT) were performed at baseline and at a 6-month follow-up. Forty-five patients successfully received a single bioresorbable everolimus drug-eluting vascular scaffold. One patient had postprocedural release of myocardial enzyme without Q-wave occurrence; 1 patient with OCT-diagnosed disruption of the scaffold caused by excessive postdilatation was treated 1 month later with a metallic drug-eluting stent. At follow-up, 3 patients declined recatheterization, 42 patients had quantitative coronary angiography, 37 had quantitative intravascular ultrasound, and 25 had OCT. Quantitative coronary angiography disclosed 1 edge restenosis (1 of 42; in-segment binary restenosis, 2.4%). At variance with the ultrasonic changes seen with the first generation of bioresorbable everolimus drug-eluting vascular scaffold at 6 months, the backscattering of the polymeric struts did not decrease over time, the scaffold area was reduced by only 2.0% with intravascular ultrasound, and no change was noted with OCT. On an intention-to-treat basis, the late lumen loss amounted to 0.19±0.18 mm with a limited relative decrease in minimal luminal area of 5.4% on intravascular ultrasound. OCT showed at follow-up that 96.8% of the struts were covered and that malapposition of at least 1 strut, initially observed in 12 scaffolds, was detected at follow-up in only 3 scaffolds. Mean neointimal growth measured by OCT between and on top of the polymeric struts equaled 1.25 mm(2), or 16.6% of the scaffold area.

CONCLUSION

Modified manufacturing process of the polymer and geometric changes in the polymeric platform have substantially improved the medium-term performance of this new generation of drug-eluting scaffold to become comparable to those of current drug eluting stents.

CLINICAL TRIAL REGISTRATION

URL: http://clinicaltrials.gov. Unique identifier: NCT00856856.

Diagnostic accuracy of 320-row multidetector computed tomography coronary angiography to noninvasively assess in-stent restenosis

OBJECTIVES

Percutaneous coronary intervention with stent implantation is routinely performed to treat patients with obstructive coronary artery disease. However, thus far, noninvasive assessment of in-stent restenosis has been challenging. Recently, 320-row multidetector computed tomography coronary angiography (CTA) was introduced, allowing volumetric image acquisition of the heart in a single heart beat or gantry rotation. The aim of this study was to evaluate the diagnostic performance of 320-row CTA in the evaluation of significant in-stent restenosis. Invasive coronary angiography (ICA) served as the standard of reference, using a quantitative approach.

MATERIALS AND METHODS

The population consisted of patients with previous coronary stent implantation who were clinically referred for cardiac evaluation because of recurrent chest pain and who underwent both CTA and ICA. CTA studies were performed using a 320-row CTA scanner with 320 detector-rows, each 0.5 mm wide, and a gantry rotation time of 350 milliseconds. Tube voltage and current were adapted to body mass index and thoracic anatomy. The entire heart was imaged in a single heart beat, with a maximum of 16-cm craniocaudal coverage. During the scan, the ECG was registered simultaneously for prospective triggering of the data. First, CTA stent image quality was assessed using a 3-point grading scale: (1) good image quality, (2) moderate image quality, and (3) poor image quality. Subsequently, the presence of in-stent restenosis was determined on a stent and patient basis by a blinded observer. Significant in-stent restenosis was defined as >or=50% luminal narrowing in the stent lumen or the presence of significant stent edge stenosis. Overlapping stents were considered to represent a single stent. Results were compared with ICA using quantitative coronary angiography. In addition, CTA stent image quality and diagnostic accuracy were related to stent characteristics and heart rate during CTA image acquisition.

RESULTS

The population consisted of 53 patients (37 men, mean age: 65 +/- 13 years) with a total of 89 stents available for evaluation. ICA identified 12 stents (13%) with significant in-stent restenosis. A total of 7 stents (8%) were of nondiagnostic CTA stent image quality, and were considered positive. Sensitivity, specificity, positive, and negative predictive values were 92%, 83%, 46%, and 98%, respectively on a stent basis. Five CTA studies (9%) were of nondiagnostic quality for the evaluation of in-stent restenosis and were considered positive. Sensitivity, specificity, positive, and negative predictive values were 100%, 81%, 58%, and 100%, respectively on a patient level. Stent diameter <3 mm as well as stent strut thickness >or=140 mum were associated with decreased CTA stent image quality and diagnostic accuracy. Heart rate during CTA acquisition and stent overlap were not associated with image degradation.

CONCLUSIONS

The present results show that 320-row CTA allows accurate noninvasive assessment of significant in-stent restenosis. However, stents with a large diameter and thin struts allowed better in-stent visualization than stents with a small diameter or thick struts. Consequently, noninvasive assessment of in-stent restenosis using CTA may be an attractive and feasible alternative particularly in carefully selected patients.

Diagnostic accuracy of 64-slice computed tomography coronary angiography for the detection of in-stent restenosis: a meta-analysis

BACKGROUND

We sought to evaluate the diagnostic accuracy of 64-slice multi-detector row computed tomography (MDCT) compared with invasive coronary angiography for in-stent restenosis (ISR) detection.

METHODS

MEDLINE, Cochrane library, and BioMed Central database searches were performed until April 2009 for original articles. Inclusion criteria were (1) 64-MDCT was used as a diagnostic test for ISR, with >50% diameter stenosis selected as the cut-off criterion for significant ISR, using invasive coronary angiography and quantitative coronary angiography as the standard of reference; (2) absolute numbers of true positive, false positive, true negative, and false negative results could be derived. Standard meta-analytic methods were applied.

RESULTS

Nine studies with a total of 598 patients with 978 stents included were considered eligible. On average, 9% of stents were unassessable (range 0-42%). Accuracy tests with 95% confidence intervals (CIs) comparing 64-MDCT vs invasive coronary angiography showed that pooled sensitivity, specificity, positive and negative likelihood ratio (random effect model) values were: 86% (95% CI 80-91%), 93% (95% CI 91-95%), 12.32 (95% CI 7.26-20.92), 0.18 (95% CI 0.12-0.28) for binary ISR detection. The symmetric area under the curve value was 0.94, indicating good agreement between 64-MDCT and invasive coronary angiography.

CONCLUSIONS

64-MDCT has a good diagnostic accuracy for ISR detection with a particularly high negative predictive value. However, still a relatively large proportion of stents remains uninterpretable. Accordingly, only in selected patients, 64-MDCT may serve as a potential alternative noninvasive method to rule out ISR.