CT Evaluation of Small-Diameter Coronary Artery Stents: Effect of an Integrated Circuit Detector with Iterative Reconstruction.

PURPOSE: To use suitable objective methods of analysis to assess the influence of the combination of an integrated-circuit computed tomographic (CT) detector and iterative reconstruction (IR) algorithms on the visualization of small (≤3-mm) coronary artery stents. MATERIALS AND METHODS: By using a moving heart phantom, 18 data sets obtained from three coronary artery stents with small diameters were investigated. A second-generation dual-source CT system equipped with an integrated-circuit detector was used. Images were reconstructed with filtered back-projection (FBP) and IR at a section thickness of 0.75 mm (FBP75 and IR75, respectively) and IR at a section thickness of 0.50 mm (IR50). Multirow intensity profiles in Hounsfield units were modeled by using a sum-of-Gaussians fit to analyze in-plane image characteristics. Out-of-plane image characteristics were analyzed with z upslope of multicolumn intensity profiles in Hounsfield units. Statistical analysis was conducted with one-way analysis of variance and the Student t test. RESULTS: Independent of stent diameter and heart rate, IR75 resulted in significantly increased xy sharpness, signal-to-noise ratio, and contrast-to-noise ratio, as well as decreased blurring and noise compared with FBP75 (eg, 2.25-mm stent, 0 beats per minute; xy sharpness, 278.2 vs 252.3; signal-to-noise ratio, 46.6 vs 33.5; contrast-to-noise ratio, 26.0 vs 16.8; blurring, 1.4 vs 1.5; noise, 15.4 vs 21.2; all P < .001). In the z direction, the upslopes were substantially higher in the IR50 reconstructions (2.25-mm stent: IR50, 94.0; IR75, 53.1; and FBP75, 48.1; P < .001). CONCLUSION: The implementation of an integrated-circuit CT detector provides substantially sharper out-of-plane resolution of coronary artery stents at 0.5-mm section thickness, while the use of iterative image reconstruction mostly improves in-plane stent visualization.

Automated quantification of epicardial adipose tissue using CT angiography: evaluation of a prototype software.

OBJECTIVES: This study evaluated the performance of a novel automated software tool for epicardial fat volume (EFV) quantification compared to a standard manual technique at coronary CT angiography (cCTA). METHODS: cCTA data sets of 70 patients (58.6 ± 12.9 years, 33 men) were retrospectively analysed using two different post-processing software applications. Observer 1 performed a manual single-plane pericardial border definition and EFVM segmentation (manual approach). Two observers used a software program with fully automated 3D pericardial border definition and EFVA calculation (automated approach). EFV and time required for measuring EFV (including software processing time and manual optimization time) for each method were recorded. Intraobserver and interobserver reliability was assessed on the prototype software measurements. T test, Spearman's rho, and Bland-Altman plots were used for statistical analysis. RESULTS: The final EFVA (with manual border optimization) was strongly correlated with the manual axial segmentation measurement (60.9 ± 33.2 mL vs. 65.8 ± 37.0 mL, rho = 0.970, P < 0.001). A mean of 3.9 ± 1.9 manual border edits were performed to optimize the automated process. The software prototype required significantly less time to perform the measurements (135.6 ± 24.6 s vs. 314.3 ± 76.3 s, P < 0.001) and showed high reliability (ICC > 0.9). CONCLUSIONS: Automated EFVA quantification is an accurate and time-saving method for quantification of EFV compared to established manual axial segmentation methods. KEY POINTS: • Manual epicardial fat volume quantification correlates with risk factors but is time-consuming. • The novel software prototype automates measurement of epicardial fat volume with good accuracy. • This novel approach is less time-consuming and could be incorporated into clinical workflow.

Reproducibility of noncalcified coronary artery plaque burden quantification from coronary CT angiography across different image analysis platforms.

OBJECTIVE: The objective of our study was to evaluate the reproducibility of noncalcified coronary artery plaque burden quantification from coronary CT angiography (CTA) across different commercial analysis platforms. MATERIALS AND METHODS: For this study, 47 patients (36 men, 11 women; mean age ± SD, 62 ± 13 years) with noncalcified plaques on coronary CTA were included. Automated quantification of noncalcified coronary artery plaque volume was performed on identical datasets using three commercially available image analysis software platforms (software platforms 1-3). Identical tissue attenuation ranges between 0 and 50 HU for low-attenuation plaques and 50-130 HU for medium-attenuation plaques were consistently applied. Log volume data were compared with the Pearson correlation coefficient and Bland-Altman analysis. RESULTS: Differences in plaque volume measurements on intraplatform repeat measurements were statistically insignificant (p = 0.923). At the low-attenuation threshold, software platform 3 had significantly higher log volumes (p < 0.001) than both software platforms 1 and 2 and software platform 1 had significantly higher log volumes than software platform 2 (p < 0.001). The results at the medium-attenuation level were identical except that the log volumes for software platforms 1 and 2 were not significantly different (p > 0.05) in the left anterior descending artery and left circumflex artery. The Pearson correlation coefficient was found to be 0.677 (p < 0.001; 95% CI, 0.608-0.735) between software platforms 1 and 2, 0.672 (p < 0.001; 95% CI, 0.603-0.732) between software platforms 1 and 3, and 0.550 (p < 0.001; 95% CI, 0.463-0.627) between software platforms 2 and 3. CONCLUSION: Currently available noncalcified plaque quantification software provides good intraplatform reproducibility but poor interplatform reproducibility. Serial or comparative assessments require evaluation using the same software. Industry standards should be developed to enable reproducible assessments across manufacturers.

Integrated cardiothoracic imaging with computed tomography.

The respiratory and the cardiovascular systems are intimately connected. Because of the high degree of morphological and functional interaction, pathophysiological processes in one compartment are likely to induce adaptive changes in the other. Computed tomography (CT) plays a central role in the diagnostic work up of both thoracic and cardiac disorders. Historically, these two systems have been evaluated separately; however, CT technology has evolved remarkably over recent decades. Up-to-date advanced imaging strategies allow for a combined assessment of the cardiopulmonary unit. Besides improved techniques of electrocardiogram (ECG)-synchronization for obtaining both morphological and functional information, latest advances of dual-source CT (DSCT) have shown great promise for even more comprehensive integrated cardiothoracic imaging.

Progression of arterial stiffness and coronary atherosclerosis: longitudinal evaluation by cardiac CT.

OBJECTIVE: We sought to use cardiac CT angiography (CTA) to longitudinally examine the relationship between changes in aortic stiffness and of the atherosclerotic burden over time. MATERIALS AND METHODS: One hundred sixty-four patients with suspected coronary artery disease underwent two retrospectively ECG-gated cardiac CTA studies an average of 12 ± 10 months apart. Arterial stiffness was represented by the aortic distensibility index (ADI) and atherosclerosis by segment involvement score (SIS) (defined as the number of coronary artery segments per patient displaying atherosclerotic plaque). Changes in ADI and SIS between the studies were compared using linear and logistic regression accounting for differences in clinical and demographic baseline characteristics. RESULTS: Age (p = 0.004), time between studies (p = 0.02), and increase in SIS (p < 0.001) were associated with a decrease in ADI on univariate analysis. Increase in SIS remained a significant independent predictor of decreased ADI on both multivariate logistic regression (with change in ADI represented categorically) and multivariate linear regression (both p < 0.001). CONCLUSION: On longitudinal evaluation with cardiac CTA, the progression of aortic stiffness is associated with the progression of coronary atherosclerosis. Although outcome studies are needed, a comprehensive assessment of vascular health with cardiac CTA, including both indexes of arterial stiffness and atherosclerotic burden, may improve risk stratification and therapy monitoring.

Interplatform reproducibility of CT coronary calcium scoring software.

PURPOSE: To investigate whether coronary artery calcium (CAC) scoring performed on three different workstations generates comparable and thus vendor-independent results. MATERIALS AND METHODS: Institutional review board and Federal Office for Radiation Protection approval were received, as was each patient's written informed consent. Fifty-nine patients (37 men, 22 women; mean age, 57 years±3 [standard deviation]) underwent CAC scoring with use of 64-section multidetector computed tomography (CT) with retrospective electrocardiographic gating (one examination per patient). Data sets were created at 10% increments of the R-R interval from 40%-80%. Two experienced observers in consensus calculated Agatston and volume scores for all data sets by using the calcium scoring software of three different workstations. Comparative analysis of CAC scores between the workstations was performed by using regression analysis, Spearman rank correlation (rs), and the Kruskal-Wallis test. RESULTS: Each workstation produced different absolute numeric results for Agatston and volume scores. However, statistical analysis revealed excellent correlation between the workstations, with highest correlation at 60% of the R-R interval (minimal rs=0.998; maximal rs=0.999) for both scoring methods. No significant differences were detected for Agatston and volume score results between the software platforms. At analysis of individual reconstruction intervals, each workstation demonstrated the same score variability, with the consequence that 12 of 59 patients were assigned to divergent cardiac risk groups by using at least one of the workstations. CONCLUSION: While mere numeric values might be different, commercially available software platforms produce comparable CAC scoring results, which suggests a vendor-independence of the method; however, none of the analyzed software platforms appears to provide a distinct advantage for risk stratification, as the variability of CAC scores depending on the reconstruction interval persists across platforms.

Coronary atherosclerosis in African American and white patients with acute chest pain: characterization with coronary CT angiography.

PURPOSE: To use coronary computed tomographic (CT) angiography to compare the prevalence, extent, and composition of coronary atherosclerotic lesions in African American and white patients with acute chest pain. MATERIALS AND METHODS: The institutional review board waived the requirement for informed consent for this retrospective, HIPAA-compliant matched-cohort study. The authors analyzed the CT angiographic data of 301 patients (150 consecutive African American patients; 151 white control patients; mean age, 55 years ± 11 [standard deviation]; 33% male) with acute chest pain. Each coronary artery segment was evaluated for presence of atherosclerotic plaque, plaque composition (calcified, noncalcified, or mixed), and stenosis. In addition, the noncalcified plaque volume was quantified by using a threshold-based automated algorithm. The presence and extent of atherosclerotic plaque were compared between the groups by using univariate and multivariate regression analyses. RESULTS: While there was no significant difference between the African American and white patients with respect to presence of any plaque (118 [79%] of 150 vs 112 [74%] of 151 patients, respectively; P = .36) or presence of stenosis (26 [17%] vs 37 [24%] patients, respectively; P = .13), the African American patients had a significantly higher prevalence (96 [64%] vs 62 [41%] patients, respectively; P < .001) and volume (median volume, 2.2 vs 1.4 mL, respectively; P < .001) of noncalcified plaque, independent of diabetes and other cardiovascular risk factors (odds ratio, 2.45; 95% confidence interval: 1.52, 4.04). In contrast, the African American patients had a lower prevalence of calcified plaque (39 [26%] vs 68 [45%] white patients, P = .001). CONCLUSION: Study results suggest that atherosclerotic plaque burden and composition, as measured by using coronary CT angiography, differ between African American and white patients, with relatively more noncalcified disease in African Americans and more calcified disease in white individuals. Further research is warranted to determine whether CT plaque characterization can improve cardiac risk prediction in African Americans.

Computer-aided detection of pulmonary embolism at CT pulmonary angiography: can it improve performance of inexperienced readers?

PURPOSE: To evaluate the effect of a computer-aided detection (CAD) algorithm on the performance of novice readers for detection of pulmonary embolism (PE) at CT pulmonary angiography (CTPA). MATERIALS AND METHODS: We included CTPA examinations of 79 patients (50 female, 52 ± 18 years). Studies were evaluated by two independent inexperienced readers who marked all vessels containing PE. After 3 months all studies were reevaluated by the same two readers, this time aided by CAD prototype. A consensus read by three expert radiologists served as the reference standard. Statistical analysis used χ(2) and McNemar testing. RESULTS: Expert consensus revealed 119 PEs in 32 studies. For PE detection, the sensitivity of CAD alone was 78%. Inexperienced readers' initial interpretations had an average per-PE sensitivity of 50%, which improved to 71% (p < 0.001) with CAD as a second reader. False positives increased from 0.18 to 0.25 per study (p = 0.03). Per-study, the readers initially detected 27/32 positive studies (84%); with CAD this number increased to 29.5 studies (92%; p = 0.125). CONCLUSION: Our results suggest that CAD significantly improves the sensitivity of PE detection for inexperienced readers with a small but appreciable increase in the rate of false positives.

Radiation-related cancer risks in a clinical patient population undergoing cardiac CT.

OBJECTIVE: The purpose of our study was to estimate cancer induction risk and generate risk conversion factors in cardiac CT angiography. MATERIALS AND METHODS: Under an institutional review board waiver and in compliance with HIPAA, we collected characteristics for a consecutive cohort of 100 patients (60 men and 40 women; mean age, 59 ± 11 years) who had previously undergone ECG-gated cardiac CT angiography on a 64-slice CT scanner. The volume CT Dose Index (CTDI(vol)) and dose-length product (DLP) were recorded and used with the ImPACT CT Patient Dosimetry Calculator to compute organ and effective doses in a standard 70 kg phantom. Patient-specific organ and effective doses were obtained by applying a weight-based correction factor. Radiation doses to radiosensitive organs were converted to risks using age- and sex-specific data published in BEIR VII. RESULTS: Median values were 62 mGy for CTDI(vol), 1,084 mGy-cm for DLP, and 17 cm for scan length. Effective doses ranged from 20 mSv (10th percentile) to 31 mSv (90th percentile). Median cancer induction risks in sensitive organs for men and women were 0.065% and 0.17%, respectively. For men and women, the range of risks was about a factor of 2. In men and women, about three quarters of the cancer risk was from lung cancer. Inclusion of the remaining less sensitive organs exposed during cardiac CT angiography examinations would likely increase the cancer induction risk by ∼20%. CONCLUSION: The average cancer induction risk in sensitive organs from cardiac CT angiography for our patient cohort was 0.13%, with a female to male cancer induction risk ratio of 2.6.

Cardiothoracic CT angiography: current contrast medium delivery strategies.

OBJECTIVE: Over the last decade, rapid technologic evolution in CT has resulted in improved spatial and temporal resolution and acquisition speed, enabling cardiothoracic CT angiography to become a viable and effective noninvasive alternative in the diagnostic algorithm. These new technologic advances have imposed new challenges for the optimization of contrast medium delivery and image acquisition strategies. CONCLUSION: Thorough understanding of contrast medium dynamics is essential for the design of effective acquisition and injection protocols. This article provides an overview of the fundamentals affecting contrast enhancement, emphasizing the modifications to contrast material delivery protocols required to optimize cardiothoracic CT angiography.

Prospective Evaluation of the First Integrated Positron Emission Tomography/Dual-Energy Computed Tomography System in Patients With Lung Cancer.

PURPOSE: The aim of this pilot study was to prospectively evaluate the first integrated positron emission tomography (PET)/dual-energy computed tomography (DECT) system performance in patients with non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: In this single-center, prospective trial, consecutive patients with NSCLC referred for a PET study between May 2017 and June 2018 were enrolled. All patients received contrast-enhanced imaging on a clinical PET/DECT system. Data analysis included PET-based standard uptake values (SUVmax) and DECT-based iodine densities of tumor masses, lymph nodes, and distant metastases. Results were analyzed using correlation tests and receiver operating characteristics curves. RESULTS: The study population was composed of 21 patients (median age 62 y, 14 male patients). A moderate positive correlation was found between iodine density values (2.2 mg/mL) and SUVmax (10.5) in tumor masses (ρ=0.53, P<0.01). Iodine density values (2.3 mg/mL) and SUVmax (5.4) of lymph node metastases showed a weak positive correlation (ρ=0.23, P=0.14). In addition, iodine quantification analysis provided no added value in differentiating between pathologic and nonpathologic lymph nodes with an area under the curve (AUC) of 0.55 using PET-based SUVmax as the reference standard. A weak positive correlation was observed between iodine density (2.2 mg/mL) and SUVmax in distant metastases (14.9, ρ=0.23, P=0.52). CONCLUSIONS: The application of an integrated PET/DECT system in lung cancer might provide additional insights in the assessment of tumor masses. However, the added value of iodine density quantification for the evaluation of lymph nodes and distant metastases seems limited.

Correlation of regional distribution and morphological pattern of calcification at CT coronary artery calcium scoring with non-calcified plaque formation and stenosis.

OBJECTIVE: To investigate whether regional calcification patterns at CT coronary artery calcium scoring (CCS) correlate with stenosis and non-calcified plaque formation. METHODS: We studied 106 patients with quantitative catheter angiography (QCA), CCS, and coronary CT angiography (cCTA). CCS was determined globally and for each artery separately. The morphological pattern of each calcification was classified as calcified nodule, shell-like, or diffuse. cCTA studies were evaluated for non-calcified plaque. The global and regional CCS and the calcification pattern were correlated with stenosis >or=50% and non-calcified plaque. RESULTS: A total of 48/106 patients had stenosis >or=50% on QCA. There was weak correlation (r = 0.36) of the global CCS with stenosis. Correlation was stronger per vessel (r = 0.55-r = 0.67). Shell-like and diffuse calcifications were significantly (p = 0.0001) more frequently associated with >or=50% stenosis and non-calcified plaque (p = 0.04) than calcified nodules. CONCLUSION: As shown before, the global CCS does not correlate well with stenosis. However, regional calcium distribution and specific patterns of calcification are correlated with stenosis and non-calcified plaque. Thus, the specificity of CT calcium scoring for identifying individuals with obstructive disease could be improved by vessel-based rather than global quantification of calcium and by differentiating specific morphological patterns of calcification.

Automated computer-aided stenosis detection at coronary CT angiography: initial experience.

OBJECTIVE: To evaluate the performance of a computer-aided algorithm for automated stenosis detection at coronary CT angiography (cCTA). METHODS: We investigated 59 patients (38 men, mean age 58 +/- 12 years) who underwent cCTA and quantitative coronary angiography (QCA). All cCTA data sets were analyzed using a software algorithm for automated, without human interaction, detection of coronary artery stenosis. The performance of the algorithm for detection of stenosis of 50% or more was compared with QCA. RESULTS: QCA revealed a total of 38 stenoses of 50% or more of which the algorithm correctly identified 28 (74%). Overall, the automated detection algorithm had 74%/100% sensitivity, 83%/65% specificity, 46%/58% positive predictive value, and 94%/100% negative predictive value for diagnosing stenosis of 50% or more on per-vessel/per-patient analysis, respectively. There were 33 false positive detection marks (average 0.56/patient), of which 19 were associated with stenotic lesions of less than 50% on QCA and 14 were not associated with an atherosclerotic surrogate. CONCLUSION: Compared with QCA, the automated detection algorithm evaluated has relatively high accuracy for diagnosing significant coronary artery stenosis at cCTA. If used as a second reader, the high negative predictive value may further enhance the confidence of excluding significant stenosis based on a normal or near-normal cCTA study.

In vitro evaluation of metallic coronary artery stents with 64-MDCT using an ECG-gated cardiac phantom: relationship between in-stent visualization, stent type, and heart rate.

OBJECTIVE: The purpose of this study was to assess the accuracy of 64-MDCT in the visualization of different coronary artery stents and in the appraisal of in-stent stenosis. MATERIALS AND METHODS: Five different coronary stent types with three diameters (2.5, 3.0, and 4.0 mm) were analyzed using anthropomorphic dynamic cardiac phantom. All stents were mounted on polyurethane sticks of defined outer diameter and contained a default concentric stenosis of 50% each. Imaging was performed at four different heart rates (no motion, 60 beats/min, 75 beats/min, and 90 beats/min). Apparent stent diameter, degree of stenosis, in-stent attenuation, and diagnostic accuracy were assessed. RESULTS: A significant (p < 0.05) overestimation of the degree of stenosis (41.1% +/- 41.4%), underestimation of the stent lumen (-42.7% +/- 41.4%), and increase in in-stent attenuation (36.6 +/- 29.2 HU) were observed for all stents and heart rates. In-stent stenosis > 50% was detected with an overall sensitivity of 88.9% (95% CI, 75.9-96.3%) and an overall specificity of 51.1% (95% CI, 35.8-66.3%) by observer 1 and with an overall sensitivity of 86.7% (95% CI, 73.2-94.9%) and an overall specificity of 57.8% (95% CI, 42.2-72.3%) by observer 2. A trend toward higher specificity was observed for increasing stent diameter, however, without reaching statistical significance (p = 0.63). CONCLUSION: In an experimental setting, 64-MDCT allows a reliable detection of instent stenosis but significantly overestimates the actual degree of stenosis. Within the range of physiologic heart rates, diagnostic accuracy is restricted by spatial, not temporal, resolution.

CT of coronary artery disease.

Technical innovation is rapidly improving the clinical utility of cardiac computed tomography (CT) and will increasingly address current technical limitations, especially the association of this test with relatively high levels of radiation. Guidelines for appropriate indications are in place and are evolving, with an increasing evidence base to ensure the appropriate use of this modality. New technologies and new applications, such as myocardial perfusion imaging and dual-energy CT, are being explored and are widening the scope of coronary CT angiography from mere coronary artery assessment to the integrative analysis of cardiac morphology, function, perfusion, and viability. The scientific evaluation of coronary CT angiography has left the stage of feasibility testing and increasingly, evidence-based data are accumulating on outcomes, prognosis, and cost-effectiveness. In this review, these developments will be discussed in the context of current pivotal transitions in cardiovascular disease management and their potential influence on the current role and future fate of coronary CT angiography will be examined.

Integrated assessment of coronary anatomy and myocardial perfusion using a retractable SPECT camera combined with 64-slice CT: initial experience.

We evaluated a prototype SPECT system integrated with multidetector row CT (MDCT) for obtaining complementary information on coronary anatomy and hemodynamic lesion significance. Twenty-five consecutive patients with known or suspected coronary artery disease (CAD) underwent routine SPECT myocardial perfusion imaging (MPI). All patients also underwent repeat MPI with a mobile SPECT unit which could be attached to a 64-slice MDCT system. Coronary CT angiography (cCTA) was performed without repositioning the patient. Investigational MPI was compared with routine MPI for detection of myocardial perfusion defects (PD). Two observers diagnosed presence or absence of CAD based on MPI alone, cCTA alone, and based on combined MPI and cCTA with fused image display. In 22/24 patients investigative MPI corresponded with routine MPI (r = 0.80). Stenosis >or= 50% at cCTA was detected in 6/24 patients. Six out of 24 patients had PD at regular MPI. Three of these six patients had no significant stenosis at cCTA. Three out of 19 patients with normal MPI studies had significant stenosis at cCTA. Our initial experience indicates that the integration of SPECT MPI with cCTA is technically feasible and enables the comprehensive evaluation of coronary artery anatomy and myocardial perfusion with a single instrumental setup.

Coronary artery plaque formation at coronary CT angiography: morphological analysis and relationship to hemodynamics.

We aimed to demonstrate that coronary CT angiography (cCTA) can be used to non-invasively study the effect of hemodynamic factors in the pathophysiology of plaque formation. cCTA data of 73 patients were analyzed. All detected plaques were classified according to location (bifurcation, non-branching segment), configuration (eccentric, concentric), orientation (myocardial, lateral, epicardial side of the vessel wall), and composition (calcified, mixed, non-calcified). Bifurcation lesions were further characterized using the Medina classification. Of 382 plaques, 8.1% were in the LM, 46.3% in the LAD, 18.3% in the LCx, and 25.9% in the RCA. Also, 25.1% were completely calcified, 72.3% were mixed, and 2.6% were purely non-calcified. Of the plaques, 51.3% were bifurcation lesions. The most frequent (40%) Medina pattern was 1.1.0 (lesion starts before, extends beyond bifurcation, sparing the side branch). Eighty percent of plaques were eccentric. A significant (p < 0.01) majority (55%) were on the myocardial side, while 17.3% were lateral, and 27.7% epicardial. Of all non-calcified and mixed plaques, 45.1% (p < 0.01) were myocardial, whereas only 14.3% were lateral, 20.6% epicardial, and 19.9% concentric. We conclude that cCTA can non-invasively study the effect of vascular hemodynamics, such as turbulent flow (bifurcations) and low shear stress (myocardial vessel wall), on the distribution and composition of atherosclerotic plaque deposition.