Coronary plaque quantification by voxel analysis: dual-source MDCT angiography versus intravascular sonography

Regression of Coronary Fatty Plaque and Risk of Cardiac Events According to Blood Pressure Status: Data From a Randomized Trial of Eicosapentaenoic Acid and Docosahexaenoic Acid in Patients With Coronary Artery Disease

Background Residual risk of cardiovascular events and plaque progression remains despite reduction in low-density lipoprotein cholesterol. Factors contributing to residual risk remain unclear. The authors examined the role of eicosapentaenoic acid and docosahexaenoic acid in coronary plaque regression and its predictors. Methods and Results A total of 240 patients with stable coronary artery disease were randomized to eicosapentaenoic acid plus docosahexaenoic acid (3.36 g/d) or none for 30 months. Patients were stratified by regression or progression of coronary fatty plaque measured by coronary computed tomographic angiography. Cardiac events were ascertained. The mean±SD age was 63.0±7.7 years, mean low-density lipoprotein cholesterol level was <2.07 mmol/L, and median triglyceride level was <1.38 mmol/L. Regressors had a 14.9% reduction in triglycerides that correlated with fatty plaque regression (r=0.135; P=0.036). Compared with regressors, progressors had higher cardiac events (5% vs 22.3%, respectively; P<0.001) and a 2.89-fold increased risk of cardiac events (95% CI, 1.1-8.0; P=0.034). Baseline non-high-density lipoprotein cholesterol level <2.59 mmol/L (100 mg/dL) and systolic blood pressure <125 mm Hg were significant independent predictors of fatty plaque regression. Normotensive patients taking eicosapentaenoic acid plus docosahexaenoic acid had regression of noncalcified coronary plaque that correlated with triglyceride reduction (r=0.35; P=0.034) and a significant decrease in neutrophil/lymphocyte ratio. In contrast, hypertensive patients had no change in noncalcified coronary plaque or neutrophil/lymphocyte ratio. Conclusions Triglyceride reduction, systolic blood pressure <125 mm Hg, and non-high-density lipoprotein cholesterol <2.59 mmol/L were associated with coronary plaque regression and reduced cardiac events. Normotensive patients had greater benefit than hypertensive patients potentially due to lower levels of inflammation. Future studies should examine the role of inflammation in plaque regression. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01624727.

Society of Cardiovascular Computed Tomography / North American Society of Cardiovascular Imaging - Expert Consensus Document on Coronary CT Imaging of Atherosclerotic Plaque

Coronary computed tomographic angiography (CCTA) provides a wealth of clinically meaningful information beyond anatomic stenosis alone, including the presence or absence of nonobstructive atherosclerosis and high-risk plaque features as precursors for incident coronary events. There is, however, no uniform agreement on how to identify and quantify these features or their use in evidence-based clinical decision-making. This statement from the Society of Cardiovascular Computed Tomography and North American Society of Cardiovascular Imaging addresses this gap and provides a comprehensive review of the available evidence on imaging of coronary atherosclerosis. In this statement, we provide standardized definitions for high-risk plaque (HRP) features and distill the evidence on the effectiveness of risk stratification into usable practice points. This statement outlines how this information should be communicated to referring physicians and patients by identifying critical elements to include in a structured CCTA report - the presence and severity of atherosclerotic plaque (descriptive statements, CAD-RADS™ categories), the segment involvement score, HRP features (e.g., low attenuation plaque, positive remodeling), and the coronary artery calcium score (when performed). Rigorous documentation of atherosclerosis on CCTA provides a vital opportunity to make recommendations for preventive care and to initiate and guide an effective care strategy for at-risk patients.

Exercise Capacity, Coronary Artery Fatty Plaque, Coronary Calcium Score, and Cardiovascular Events in Subjects With Stable Coronary Artery Disease

Background

Aerobic exercise capacity is inversely associated with cardiovascular and all‐cause mortality in men and women without coronary artery disease (CAD); however, a higher amount of vigorous exercise is associated with a J‐shaped relationship in CAD patients. Therefore, the optimal type and amount of exercise for CAD patients is unclear. Coronary artery calcification (CAC) is associated with increased cardiovascular disease (CVD) events and mortality. Fatty plaque is more likely to rupture and cause coronary events than other types. We examined the association between exercise capacity, fatty plaque, CAC score and CVD events in CAD patients.

Methods and Results

A total of 270 subjects with stable CAD were divided into tertiles based on metabolic equivalents of task (METs) calculated from exercise treadmill testing. Self‐reported exercise was obtained. Coronary computed tomographic angiography measured coronary plaque volume and CAC score. After adjustment, fatty plaque volume was not different among the 3 MET groups. For each 1 MET increase, CAC was 66.2 units lower (P=0.017). Those with CAC >400 and ≥8.2 METs had fewer CVD events over 30 months compared to <8.2 METs (P=0.037). Of moderate intensity exercisers (median, 240 min/wk; 78% walking only), 62.4% achieved ≥8.2 METs and lower CAC scores (P=0.07). Intensity and duration of exercise had no adverse impact on coronary plaque or CVD events.

Conclusions

Achieving ≥8.2 METs with moderate exercise intensity and volume as walking resulted in lower CAC scores and fewer CVD events. Therefore, vigorous exercise intensity and volume may not be needed for CAD patients to derive benefit.

Registration

URL: https://www.clinicaltrials.gov; Unique Identifier: NCT01624727.

An omega-3 fatty acid plasma index ≥4% prevents progression of coronary artery plaque in patients with coronary artery disease on statin treatment

BACKGROUND AND AIMS

Higher blood levels of the omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been associated with fewer cardiovascular events and lower mortality in prospective studies. Our aim was to determine a target level of EPA and DHA to prevent progression of coronary artery plaque.

METHODS

218 subjects with stable coronary artery disease on statins were randomized to high-dose EPA and DHA (3.36 g daily) or no omega-3 for 30 months. Coronary plaque volume was measured by coronary computed tomographic angiography. Plasma phospholipid levels of EPA, DHA and total fatty acids were measured by gas chromatography mass spectrometry. The omega-3 fatty acid index was calculated as EPA+DHA/total fatty acid.

RESULTS

Mean (SD) age was 62.9 (7.8) years; mean (SD) LDL-C level 78.6 (27.3) mg/dL and median triglyceride level 122 mg/dL. Subjects assigned to EPA and DHA had increased plasma EPA and DHA levels variably from 1.85% to 13.02%. Plasma omega-3 fatty acid index ≥4% prevented progression of fibrous, noncalcified, calcified and total plaque in nondiabetic subjects whereas those in the lowest quartile (<3.43%) had significant progression of fibrous, calcified and total plaque. No difference was observed in diabetic subjects.

CONCLUSIONS

EPA and DHA added to statins prevented coronary plaque progression in nondiabetic subjects with mean LDL-C <80 mg/dL, when an omega-3 index ≥4% was achieved. Low omega-3 index <3.43% identified nondiabetic subjects at risk of coronary plaque progression despite statin therapy. These findings highlight the importance of measuring plasma levels of omega-3 fatty acids early and at trial conclusion. Targeting an omega-3 index ≥4% maximizes cardiovascular benefit.

Diastolic blood pressure predicts coronary plaque volume in patients with coronary artery disease

BACKGROUND AND AIMS

Hypertension is associated with increased clinical and subclinical coronary artery disease (CAD); however, the relationship between blood pressure and coronary plaque volume is unclear. We examined the effect of systolic blood pressure (SBP) and diastolic blood pressure (DBP) on coronary artery plaque volume.

METHODS

285 subjects with stable CAD on statin therapy underwent coronary computed tomographic angiography to measure volume of fatty, fibrous, noncalcified, calcified and total coronary plaque.

RESULTS

Mean (SD) age was 63.1 (7.7); mean (SD) LDL-C, 78.7 mg/dL (28.5). Compared to the highest DBP tertile (>76 mmHg), those in the lowest DBP tertile (≤68 mmHg) had lower volumes of fatty: 10.0 vs. 7.7 mm³/mm, (p trend = 0.042), fibrous: 19.6 vs. 13.8 mm³/mm (p trend = 0.011), non-calcified: 29.7 vs. 22.5 mm³/mm (p trend = 0.017) and total plaque: 37.8 vs. 25.1 mm³/mm (p trend = 0.010) whereas there was no relationship with SBP tertiles. Similarly, when examined as a continuous variable, higher DBP was a significant independent predictor of higher plaque volume after multivariate adjustment: for every 1 mmHg increase in DBP, fibrous plaque increased 0.128 mm³/mm (p = 0.022), noncalcified plaque increased 0.176 mm³/mm (p = 0.045), calcified plaque increased 0.096 mm³/mm (p = 0.001) and total plaque increased 0.249 mm³/mm (p = 0.019) whereas SBP ranging from 95 to 154 mmHg did not predict plaque volume.

CONCLUSIONS

Level of DBP predicts coronary plaque with a DBP tertile ≤68 mmHg associated with the least amount of coronary plaque in subjects with LDL-C < 80 mg/dL.

Effect of Eicosapentaenoic and Docosahexaenoic Acids Added to Statin Therapy on Coronary Artery Plaque in Patients With Coronary Artery Disease: A Randomized Clinical Trial

Background

Although statins reduce cardiovascular events, residual risk remains. Therefore, additional modalities are needed to reduce risk. We evaluated the effect of eicosapentaenoic acid and docosahexaenoic acid in pharmacologic doses added to statin treatment on coronary artery plaque volume.

Methods and Results

A total of 285 subjects with stable coronary artery disease on statins were randomized to omega‐3 ethyl‐ester (1.86 g of eicosapentaenoic acid and 1.5 g of docosahexaenoic acid daily) or no omega‐3 (control) for 30 months. Coronary plaque volume was assessed by coronary computed tomographic angiography. Mean (SD) age was 63.0 (7.7) years; mean low‐density lipoprotein cholesterol ≤80 mg/dL. In the intention‐to‐treat analysis, our primary endpoint, noncalcified plaque volume, was not different between groups (P=0.14) but approached significance in the per protocol analysis (P=0.07). When stratified by age in the intention‐to‐treat analysis, younger omega‐3 subjects had significantly less progression of the primary endpoint, noncalcified plaque (P=0.013), and fibrous, calcified and total plaque. In plaque subtype analysis, controls had significant progression of fibrous plaque compared to no change in the omega‐3 ethyl‐ester group (median % change [interquartile range], 5.0% [−5.7, 20.0] versus −0.1% [−12.3, 14.5], respectively; P=0.018). Among those on low‐intensity statins, omega‐3 ethyl‐ester subjects had attenuation of fibrous plaque progression compared to controls (median % change [interquartile range], 0.3% [−12.8, 9.0] versus 4.8% [−5.1, 19.0], respectively; P=0.032). In contrast, those on high‐intensity statins had no difference in plaque change in either treatment arm.

Conclusions

High‐dose eicosapentaenoic acid and docosahexaenoic acid provided additional benefit to statins in preventing progression of fibrous coronary plaque in subjects adherent to therapy with well‐controlled low‐density lipoprotein cholesterol levels. The benefit on low‐intensity statin, but not high‐intensity statin, suggests that statin intensity affects plaque volume.

Clinical Trial Registration

URL: http://www.ClinicalTrials.gov. Unique identifier: NCT01624727.

Framework for detection and localization of coronary non-calcified plaques in cardiac CTA using mean radial profiles

BACKGROUND AND OBJECTIVE

The high mortality rate associated with coronary heart disease (CHD) has driven intensive research in cardiac imaging and image analysis. The advent of computed tomography angiography (CTA) has turned non-invasive diagnosis of cardiovascular anomalies into reality as calcified coronary plaques can be easily identified due to their high intensity values. However, the detection of non-calcified plaques in CTA is still a challenging problem because of lower intensity values, which are often similar to the nearby blood and muscle tissues. In this work, we propose the use of mean radial profiles for the detection of non-calcified plaques in CTA imagery.

METHODS

Accordingly, we computed radial profiles by averaging the image intensity in concentric rings around the vessel centreline in a first stage. In the subsequent stage, an SVM classifier is applied to identify the abnormal coronary segments. For occluded segments, we further propose a derivative-based method to localize the position and length of the plaque inside the segment.

RESULTS

A total of 32 CTA volumes were analysed and a detection accuracy of 88.4% with respect to the manual expert was achieved. The plaque localization accuracy was computed using the Dice similarity coefficient and a mean of 83.2% was achieved.

CONCLUSION

The consistent performance for multi-vendor, multi-institution data demonstrates the reproducibility of our method across different CTA datasets with a good agreement with manual expert annotations.

Computed tomography-based high-risk coronary plaque score to predict acute coronary syndrome among patients with acute chest pain--Results from the ROMICAT II trial

BACKGROUND

Coronary computed tomography angiography (CTA) can be used to detect and quantitatively assess high-risk plaque features.

OBJECTIVE

To validate the ROMICAT score, which was derived using semi-automated quantitative measurements of high-risk plaque features, for the prediction of ACS.

MATERIAL AND METHODS

We performed quantitative plaque analysis in 260 patients who presented to the emergency department with suspected ACS in the ROMICAT II trial. The readers used a semi-automated software (QAngio, Medis medical imaging systems BV) to measure high-risk plaque features (volume of <60HU plaque, remodeling index, spotty calcium, plaque length) and diameter stenosis in all plaques. We calculated a ROMICAT score, which was derived from the ROMICAT I study and applied to the ROMICAT II trial. The primary outcome of the study was diagnosis of an ACS during the index hospitalization.

RESULTS

Patient characteristics (age 57 ± 8 vs. 56 ± 8 years, cardiovascular risk factors) were not different between those with and without ACS (prevalence of ACS 7.8%). There were more men in the ACS group (84% vs. 59%, p = 0.005). When applying the ROMICAT score derived from the ROMICAT I trial to the patient population of the ROMICAT II trial, the ROMICAT score (OR 2.9, 95% CI 1.4-6.0, p = 0.003) was a predictor of ACS after adjusting for gender and ≥ 50% stenosis. The AUC of the model containing ROMICAT score, gender, and ≥ 50% stenosis was 0.91 (95% CI 0.86-0.96) and was better than with a model that included only gender and ≥ 50% stenosis (AUC 0.85, 95%CI 0.77-0.92; p = 0.002).

CONCLUSIONS

The ROMICAT score derived from semi-automated quantitative measurements of high-risk plaque features was an independent predictor of ACS during the index hospitalization and was incremental to gender and presence of ≥ 50% stenosis.

Quantitative volumetric imaging of normal, neoplastic and hyperplastic mouse prostate using ultrasound

Background

Genetically engineered mouse models are essential to the investigation of the molecular mechanisms underlying human prostate pathology and the effects of therapy on the diseased prostate. Serial in vivo volumetric imaging expands the scope and accuracy of experimental investigations of models of normal prostate physiology, benign prostatic hyperplasia and prostate cancer, which are otherwise limited by the anatomy of the mouse prostate. Moreover, accurate imaging of hyperplastic and tumorigenic prostates is now recognized as essential to rigorous pre-clinical trials of new therapies. Bioluminescent imaging has been widely used to determine prostate tumor size, but is semi-quantitative at best. Magnetic resonance imaging can determine prostate volume very accurately, but is expensive and has low throughput. We therefore sought to develop and implement a high throughput, low cost, and accurate serial imaging protocol for the mouse prostate.

Methods

We developed a high frequency ultrasound imaging technique employing 3D reconstruction that allows rapid and precise assessment of mouse prostate volume. Wild-type mouse prostates were examined (n = 4) for reproducible baseline imaging, and treatment effects on volume were compared, and blinded data analyzed for intra- and inter-operator assessments of reproducibility by correlation and for Bland-Altman analysis. Examples of benign prostatic hyperplasia mouse model prostate (n = 2) and mouse prostate implantation of orthotopic human prostate cancer tumor and its growth (n = 6) are also demonstrated.

Results

Serial measurement volume of the mouse prostate revealed that high frequency ultrasound was very precise. Following endocrine manipulation, regression and regrowth of the prostate could be monitored with very low intra- and interobserver variability. This technique was also valuable to monitor the development of prostate growth in a model of benign prostatic hyperplasia. Additionally, we demonstrate accurate ultrasound image-guided implantation of orthotopic tumor xenografts and monitoring of subsequent tumor growth from ~10 to ~750 mm³ volume.

Discussion

High frequency ultrasound imaging allows precise determination of normal, neoplastic and hyperplastic mouse prostate. Low cost and small image size allows incorporation of this imaging modality inside clean animal facilities, and thereby imaging of immunocompromised models. 3D reconstruction for volume determination is easily mastered, and both small and large relative changes in volume are accurately visualized. Ultrasound imaging does not rely on penetration of exogenous imaging agents, and so may therefore better measure poorly vascularized or necrotic diseased tissue, relative to bioluminescent imaging (IVIS).

Conclusions

Our method is precise and reproducible with very low inter- and intra-observer variability. Because it is non-invasive, mouse models of prostatic disease states can be imaged serially, reducing inter-animal variability, and enhancing the power to detect small volume changes following therapeutic intervention.

Non-calcified coronary atherosclerotic plaque characterization by dual energy computed tomography

Coronary heart disease (CHD) is the most prevalent cause of death worldwide. Atherosclerosis which is the condition of plaque buildup on the inside of the coronary artery wall is the main cause of CHD. Rupture of unstable atherosclerotic coronary plaque is known to be the cause of acute coronary syndrome. Vulnerability of atherosclerotic plaque has been related to a large lipid core covered by a fibrous cap. Non-invasive assessment of plaque characterization is necessary due to prognostic importance of early stage identification. The purpose of this study is to use the additional attenuation data provided by dual energy computed tomography (DECT) for plaque characterization. We propose to train supervised learners on pixel values recorded from DECT monochromatic X-ray and material basis pairs images, for more precise classification of fibrous and lipid plaques. The interaction of the pixel values from different image types is taken into consideration, as single pixel value might not be informative enough to separate fibrous from lipid. Organic phantom plaques scanned in a fabricated beating heart phantom were used as ground truth to train the learners. Our results show that support vector machines, artificial neural networks and random forests provide accurate results both on phantom and patient data.

Interscan reproducibility of quantitative coronary plaque volume and composition from CT coronary angiography using an automated method

OBJECTIVES

Quantitative measurements of coronary plaque volume may play a role in serial studies to determine disease progression or regression. Our aim was to evaluate the interscan reproducibility of quantitative measurements of coronary plaque volumes using a standardized automated method.

METHODS

Coronary dual source computed tomography angiography (CTA) was performed twice in 20 consecutive patients with known coronary artery disease within a maximum time difference of 100 days. The total plaque volume (TP), the volume of non-calcified plaque (NCP) and calcified plaque (CP) as well as the maximal remodelling index (RI) were determined using automated software.

RESULTS

Mean TP volume was 382.3 ± 236.9 mm(3) for the first and 399.0 ± 247.3 mm(3) for the second examination (p = 0.47). There were also no significant differences for NCP volumes, CP volumes or RI. Interscan correlation of the plaque volumes was very good (Pearson's correlation coefficients: r = 0.92, r = 0.90 and r = 0.96 for TP, NCP and CP volumes, respectively).

CONCLUSIONS

Automated software is a time-saving method that allows accurate assessment of coronary atherosclerotic plaque volumes in coronary CTA with high reproducibility. With this approach, serial studies appear to be possible.

KEY POINTS

Reproducibility of coronary atherosclerotic plaque volume in coronary CTA is high. Using automated software facilitates quantitative measurements. Serial studies to determine progression or regression of coronary plaque are possible.

Comprehensive plaque assessment by coronary CT angiography

Most acute coronary syndromes are caused by sudden luminal thrombosis due to atherosclerotic plaque rupture or erosion. Preventing such an event seems to be the only effective strategy to reduce mortality and morbidity of coronary heart disease. Coronary lesions prone to rupture have a distinct morphology compared with stable plaques, and provide a unique opportunity for noninvasive imaging to identify vulnerable plaques before they lead to clinical events. The submillimeter spatial resolution and excellent image quality of modern computed tomography (CT) scanners allow coronary atherosclerotic lesions to be detected, characterized, and quantified. Large plaque volume, low CT attenuation, napkin-ring sign, positive remodelling, and spotty calcification are all associated with a high risk of acute cardiovascular events in patients. Computation fluid dynamics allow the calculation of lesion-specific endothelial shear stress and fractional flow reserve, which add functional information to plaque assessment using CT. The combination of morphologic and functional characteristics of coronary plaques might enable noninvasive detection of vulnerable plaques in the future.

A voxel-map quantitative analysis approach for atherosclerotic noncalcified plaques of the coronary artery tree

Noncalcified plaques (NCPs) are associated with the presence of lipid-core plaques that are prone to rupture. Thus, it is important to detect and monitor the development of NCPs. Contrast-enhanced coronary Computed Tomography Angiography (CTA) is a potential imaging technique to identify atherosclerotic plaques in the whole coronary tree, but it fails to provide information about vessel walls. In order to overcome the limitations of coronary CTA and provide more meaningful quantitative information for percutaneous coronary intervention (PCI), we proposed a Voxel-Map based on mathematical morphology to quantitatively analyze the noncalcified plaques on a three-dimensional coronary artery wall model (3D-CAWM). This approach is a combination of Voxel-Map analysis techniques, plaque locating, and anatomical location related labeling, which show more detailed and comprehensive coronary tree wall visualization.

How to assess non-calcified plaque in CT angiography: delineation methods affect diagnostic accuracy of low-attenuation plaque by CT for lipid-core plaque in histology

AIMS

To compare the accuracy of two plaque delineation methods for coronary computed tomographic angiography (CTA) to identify lipid-core plaque (LCP) using histology as the reference standard.

METHODS AND RESULTS

Five ex vivo hearts were analysed by CTA and histology. LCP was defined by histology as fibroatheroma with core diameter/circumference >200 μm/>60° and cap thickness <450 μm. In CTA, plaque was manually delineated either as the difference between the inner and outer vessel walls (Method A) or as a direct tracing of plaque (Method B). Low-attenuation plaque was defined as an area with <90 Hounsfield units. Of 446 co-registered cross-sections, 55 (12%) contained LCP. In CTA, low-attenuation plaque area was larger as assessed with Method A compared with Method B (difference: 120 ± 60%). Although low-attenuation plaque was associated with the presence of LCP, the delineation Method B yielded higher diagnostic accuracy than Method A [area under the curve (AUC): 0.831 vs. 0.780, respectively, P = 0.005]. After excluding 'normal' cross-sections by CTA (n = 117), AUC for detecting LCP became similar between both methods (0.767 vs. 0.729, P = 0.07, respectively).

CONCLUSION

Low-attenuation plaque in CTA is a diagnostic tool for LCP but prone to error if plaque is defined as the area between the inner and outer vessel walls and normal cross-sections are included in the assessment.

Beyond Coronary Stenosis: Coronary Computed Tomographic Angiography for the Assessment of Atherosclerotic Plaque Burden

Coronary computed tomographic angiography (CCTA) is emerging as a key non-invasive method for assessing cardiovascular risk by measurement of coronary stenosis and coronary artery calcium (CAC). New advancements in CCTA technology have led to the ability to directly identify and quantify the so-called "vulnerable" plaques that have features of positive remodeling and low density components. In addition, CCTA presents a new opportunity for noninvasive measurement of total coronary plaque burden that has not previously been available. The use of CCTA needs also to be balanced by its risks and, in particular, the associated radiation exposure. We review current uses of CCTA, CCTA's ability to measure plaque quantity and characteristics, and new developments in risk stratification and CCTA technology. CCTA represents a quickly developing field that will play a growing role in the non-invasive management of cardiovascular disease.

Comparison of iodinated contrast media for the assessment of atherosclerotic plaque attenuation values by CT coronary angiography: observations in an ex vivo model

OBJECTIVE

To compare the influence of different iodinated contrast media with several dilutions on plaque attenuation in an ex vivo coronary model studied by multislice CT coronary angiography.

METHODS

In six ex vivo left anterior descending coronary arteries immersed in oil, CT (slices/collimation 64×0.625 mm, temporal resolution 210 ms, pitch 0.2) was performed after intracoronary injection of a saline solution, and solutions of a dimeric isosmolar contrast medium (Iodixanol 320 mgI ml(-1)) and a monomeric high-iodinated contrast medium (Iomeprol 400 mgI ml(-1)) with dilutions of 1/80 (low concentration), 1/50 (medium concentration), 1/40 (high concentration) and 1/20 (very high concentration). Two radiologists drew regions of interest in the lumen and in calcified and non-calcified plaques for each solution. 29 cross-sections with non-calcified plaques and 32 cross-sections with calcified plaques were evaluated.

RESULTS

Both contrast media showed different attenuation values within lumen and plaque (p<0.0001). The correlation between lumen and non-calcified plaque values was good (Iodixanol r=0.793, Iomeprol r=0.647). Clustered medium- and high-concentration solutions showed similar plaque attenuation values, signal-to-noise ratios (SNRs) (non-calcified plaque: medium solution SNR 31.3±15 vs 31.4±20, high solution SNR 39.4±17 vs 37.4±22; calcified plaque: medium solution SNR 305.2±133 vs 298.8±132, high solution SNR 323.9±138 vs 293±123) and derived contrast-to-noise ratios (p>0.05).

CONCLUSION

Differently iodinated contrast media have a similar influence on plaque attenuation profiles.

ADVANCES IN KNOWLEDGE

Since iodine load affects coronary plaque attenuation linearly, different contrast media may be equally employed for coronary atherosclerotic plaque imaging.

Comparison of coronary plaque subtypes in male and female patients using 320-row MDCTA

OBJECTIVE

Determine plaque subtype and volume difference in male and female patients with obstructive and non-obstructive CAD using 320-row MDCTA.

MATERIALS AND METHODS

128 patients with suspected CAD underwent MDCTA. All studies were divided into two groups based on disease severity. 0-70% stenosis (non-obstructive CAD) & >70% (obstructive). All were compared for plaque quantity and subtypes by gender. Main arteries, RCA, LM, LAD and LCX were analyzed using Vitrea 5.2 software to quantify fatty, fibrous and calcified plaque. Thresholds for coronary plaque quantification (volume in mm(3)) were preset at 35 ± 12 HU for fatty, 90 ± 24 HU for fibrous and >130 HU for calcified/mixed plaque and analyzed using STATA software.

RESULTS

Total plaque burden in 118 patients [65M: 53F] was significantly higher in all arteries in males compared to females with non-obstructive disease. Total plaque volume for males vs. females was: RCA: 10.10 ± 5.02 mm(3) vs. 6.89 ± 2.75 mm(3), respectively, p = 0.001; LAD: 7.21 ± 3.38 mm(3) vs. 5.89 ± 1.93 mm(3), respectively, p = 0.04; LCX: 9.13 ± 3.27 mm(3) vs. 7.16 ± 1.73 mm(3), respectively, p = 0.002; LM 15.13 ± 4.51 mm(3) vs. 11.85 ± 4.03 mm(3), respectively, p = 0.001. In sub-analyses, males had significantly more fibrous and fatty plaque in LM, LAD & LCX than females. However in the RCA, only fibrous plaque was significantly greater in males. Calcified plaque volume was not significantly different in both genders. Only 8% of patients had obstructive CAD (>70% stenosis); there was no significant difference in plaque volume or subtypes.

CONCLUSION

In patients with non-obstructive CAD, males were found to have significantly higher total coronary plaque volume with predominance of fibrous and fatty subtypes compared to females of the same age and BMI. There was no significant difference in plaque subtype or volume in patients with obstructive disease.

Differentiation of early from advanced coronary atherosclerotic lesions: systematic comparison of CT, intravascular US, and optical frequency domain imaging with histopathologic examination in ex vivo human hearts

PURPOSE

To establish an ex vivo experimental setup for imaging coronary atherosclerosis with coronary computed tomographic (CT) angiography, intravascular ultrasonography (US), and optical frequency domain imaging (OFDI) and to investigate their ability to help differentiate early from advanced coronary plaques.

MATERIALS AND METHODS

All procedures were performed in accordance with local and federal regulations and the Declaration of Helsinki. Approval of the local Ethics Committee was obtained. Overall, 379 histologic cuts from nine coronary arteries from three donor hearts were acquired, coregistered among modalities, and assessed for the presence and composition of atherosclerotic plaque. To assess the discriminatory capacity of the different modalities in the detection of advanced lesions, c statistic analysis was used. Interobserver agreement was assessed with the Cohen κ statistic.

RESULTS

Cross sections without plaque at coronary CT angiography and with fibrous plaque at OFDI almost never showed advanced lesions at histopathologic examination (odds ratio [OR]: 0.02 and 0.06, respectively; both P<.0001), while mixed plaque at coronary CT angiography, calcified plaque at intravascular US, and lipid-rich plaque at OFDI were associated with advanced lesions (OR: 2.49, P=.0003; OR: 2.60, P=.002; and OR: 31.2, P<.0001, respectively). OFDI had higher accuracy for discriminating early from advanced lesions than intravascular US and coronary CT angiography (area under the receiver operating characteristic curve: 0.858 [95% confidence interval {CI}: 0.802, 0.913], 0.631 [95% CI: 0.554, 0.709], and 0.679 [95% CI: 0.618, 0.740]; respectively, P<.0001). Interobserver agreement was excellent for OFDI and coronary CT angiography (κ=0.87 and 0.85, respectively) and was good for intravascular US (κ=0.66).

CONCLUSION

Systematic and standardized comparison between invasive and noninvasive modalities for coronary plaque characterization in ex vivo specimens demonstrated that coronary CT angiography and intravascular US are reasonably associated with plaque composition and lesion grading according to histopathologic findings, while OFDI was strongly associated. These data may help to develop initial concepts of sequential imaging strategies to identify patients with advanced coronary plaques.

Coronary atherosclerosis imaging by coronary CT angiography: current status, correlation with intravascular interrogation and meta-analysis

Coronary computed tomography angiography (CTA) allows coronary artery visualization and the detection of coronary stenoses. In addition; it has been suggested as a novel, noninvasive modality for coronary atherosclerotic plaque detection, characterization, and quantification. Emerging data show that coronary CTA-based semiquantitative plaque characterization and quantification are sufficiently reproducible for clinical purposes, and fully quantitative approaches may be appropriate for use in clinical trials. Furthermore, several lines of investigation have validated plaque imaging by coronary CTA against other imaging modalities such as intravascular ultrasound/"virtual histology" and optical coherence tomography, and there are emerging data using biochemical modalities such as near-infrared spectroscopy. Finally, clinical validation in patients with acute coronary syndrome and in the outpatient setting has shown incremental value of CTA-based plaque characterization for the prediction of major cardiovascular events. With recent developments in image acquisition and reconstruction technologies, coronary CTA can be performed with relatively low radiation exposure. With further technological innovation and clinical research, coronary CTA may become an important tool in the quest to identify vulnerable plaques and the at-risk patient.

3D quantitative evaluation of atherosclerotic plaque based on rotational angiography

BACKGROUND AND PURPOSE

Atherosclerosis is a systemic disease that has been shown to cause various cardiovascular diseases and stroke. However, technologies to evaluate the volume of atherosclerotic plaque are limited. We present a method for determination of 3D plaque volume based on RA.

MATERIALS AND METHODS

3DRA images obtained from patients were used to evaluate the plaque. Six patients who were diagnosed with atherosclerotic lesions were included. The PR model developed for 3DRA was applied to analyze the geometry of the vessel and calculate the plaque volume. To validate the present method, we tested computer-generated phantoms with different degrees of stenosis.

RESULTS

Application of PR to clinical cases allowed the estimation of plaque morphology and quantification of plaque volume. Technique validation showed that on average, PR can rebuild 92% of the plaque and provide satisfactory determination of plaque volume.

CONCLUSIONS

A new approach to obtain plaque volume based on 3DRA is presented. The initial tests in 6 clinical cases and validation with different phantoms showed that this method is feasible. Further validation in a larger clinical series is required to assess the ultimate value of the present technique.

TNF is necessary for castration-induced prostate regression, whereas TRAIL and FasL are dispensable

TNF, a proinflammatory and immune-regulatory cytokine, is a potent apoptotic stimulus in vitro. However, there have been few examples of a physiologic role for TNF-induced apoptosis in vivo. Here, we describe a novel role for TNF in prostate epithelial cell apoptosis after androgen withdrawal. Employing high-resolution serial magnetic resonance imaging to measure mouse prostate volume changes over time, we demonstrate that the extent of castration-induced prostate regression is significantly reduced in mice null for either the Tnf or Tnfr1 genes but not mice deficient for TNF-related apoptosis-inducing ligand or Fas signaling. Wild-type mice receiving soluble TNF (sTNF) receptor 2 (to bind TNF and block signaling) before castration exhibit an identical reduction of prostate regression. Together, these data indicate that uniquely among known extrinsic death signals, TNF is required for castration-induced prostate regression. Additionally, membrane-bound TNF protein and stromal cell specific TNF mRNA levels increase in rat prostate after castration. This is consistent with a paracrine role for TNF in prostate regression. When injected into the peritoneum of Tnf(-/-) mice at the time of castration, sTNF restores normal levels of prostate regression. However, wild-type mice receiving sTNF in the absence of castration do not exhibit prostate regression, indicating that TNF alone is not sufficient but acts in the context of additional castration-induced signals. These findings support a physiologic role for TNF in prostate regression after androgen withdrawal. Understanding this role may lead to novel therapies for prostate cancer.

[What factors affected image quality in coronary multidetector-row computed tomography?]

BACKGROUND

Although it is well known that we usually cannot acquire a high quality coronary MDCT in patients with arrhythmia or incomplete breath-hold, we sometimes also cannot obtain a high quality coronary MDCT in patients without arrhythmia or incomplete breath-hold.

PURPOSE

We studied what factors other than arrhythmia or incomplete breath-hold affected image quality.

METHODS

Coronary MDCT and echocardiography were performed within one month in 2145 patients, and 452 cases of arrhythmia or 102 cases of incomplete breath-hold during scanning were eliminated. The remaining 1591 patients were studied. Those patients were divided into two groups (mid-diastolic phase reconstruction (MD) group (N=1377) and end-systolic phase reconstruction (ES) group (N=214)). Age, body weight, mean heart rate (HR) during scanning, temporal resolution (TR) and left ventricular ejection fraction (LVEF) by echocardiography were estimated. Image quality (A: Excellent (3 points), B: Acceptable (2 points), C: Unacceptable (1 point)) was evaluated.

RESULTS

The mean image quality points of the MD group (2.9±0.3) were significantly (P<0.0001) higher than the mean image quality points of the ES group (2.3±0.7), and the mean HR of the MD group (57±6 bpm) was significantly (P<0.0001) lower than that of the ES group (81±15 bpm). In the MD group, HR and TR were selected as significant factors affecting image quality by stepwise regression analysis. In the ES group, TR and HR were selected. In the ES subgroup with HR<90 bpm, TR and HR were selected; however, in the ES subgroup with HR≥90 bpm, TR and LVEF were selected.

CONCLUSION

In the MD group, low HR was important for high quality coronary MDCT. In the ES subgroup with HR<90, short TR and low HR were important; however, in the ES subgroup with HR≥90 bpm, TR and LVEF were more important than HR.

Automated three-dimensional quantification of noncalcified coronary plaque from coronary CT angiography: comparison with intravascular US

PURPOSE

To determine the accuracy of a previously developed automated algorithm (AUTOPLAQ [APQ]) for rapid volumetric quantification of noncalcified and calcified plaque from coronary computed tomographic (CT) angiography in comparison with intravascular ultrasonography (US).

MATERIALS AND METHODS

This study was approved by the institutional review board and was HIPAA compliant; all patients provided written informed consent. APQ combines derived scan-specific attenuation threshold levels for lumen, plaque, and knowledge-based segmentation of coronary arteries for quantification of plaque components. APQ was validated with retrospective analysis of 22 coronary atherosclerotic plaques in 20 patients imaged with coronary CT angiography and intravascular US within 2 days of each other. Coronary CT angiographic data were acquired by using dual-source CT. For each patient, well-defined plaques without calcifications were selected, and plaque volume was measured with APQ and manual tracing at CT and with intravascular US. Measurements were compared with paired t test, correlation, and Bland-Altman analysis.

RESULTS

There was excellent correlation between noncalcified plaque volumes quantified with APQ and intravascular US (r = 0.94, P < .001), with no significant differences (P = .08). Mean plaque volume with intravascular US was 105.9 mm³ ± 83.5 (standard deviation) and with APQ was 116.6 mm³ ± 80.1. Mean plaque volume with manual tracing from CT was 100.8 mm³ ± 81.7 and with APQ was 116.6 mm³ ± 80.1, with excellent correlation (r = 0.92, P < .001) and no significant differences (P = .23).

CONCLUSION

Automated scan-specific threshold level-based quantification of plaque components from coronary CT angiography allows rapid, accurate measurement of noncalcified plaque volumes, compared with intravascular US, and requires a fraction of the time needed for manual analysis.

Methods of plaque quantification and characterization by cardiac computed tomography

The pathologic evolution of coronary artery atherosclerosis occurs slowly over decades, which may provide an opportunity for diagnostic imaging to identify patients before clinical events evolve. Cardiac computed tomography (CT) is an emerging noninvasive imaging tool, which can visualize the entire coronary tree with submillimeter resolution. We reviewed the current status of cardiac CT to qualitatively and quantitatively determine coronary plaque dimensions and composition, and its potential to improve our understanding of the natural history of coronary artery disease as well as prevention of cardiovascular events.