A rosetta stone for coronary calcium risk stratification: agatston, volume, and mass scores in 11,490 individuals

PCSK9 and Coronary Artery Plaque-New Opportunity or Red Herring?

PURPOSE OF REVIEW

Although the clinical benefit of reducing low-density lipoprotein cholesterol (LDLc) in patients with coronary artery disease (CAD) is well-established, the impact on plaque composition and stability is less clear. Our narrative review aimed to assess the clinical effects of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors on coronary plaque characteristics specifically focusing from atheroma progression to regression and stabilization.

RECENT FINDINGS

The combination of statin therapy and PCSK9 inhibitors (evolocumab and alirocumab) promotes plaque stability in patients following an acute coronary syndrome. The GLAGOV study highlighted the relationship between achieved LDLc levels and changes in percentage atheroma volume. Similarly, the PACMAN-AMI study concluded that the qualitative and quantitative changes in coronary plaque were associated with the levels of LDLc. Assessing the severity of coronary artery stenosis and the extent of atherosclerotic burden by means of imaging techniques (e.g., IVUS, OCT and near-infrared spectroscopic) have significantly advanced our understanding of the benefits from promoting plaque regression and achieving to features of plaque stabilization through increasingly intensive lipid-lowering strategies.

Hybrid Imaging: Calcium Score and Myocardial Perfusion Imaging

Coronary heart disease (CHD) remains the top cause of death due to cardiovascular conditions worldwide, with someone suffering a myocardial infarction every 40 seconds. This highlights the importance of non-invasive imaging technologies like myocardial perfusion imaging (MPI), which are crucial for detecting coronary artery disease (CAD) early, even before symptoms appear. However, the reliance solely on MPI has shifted due to its limitations in definitively ruling out atherosclerosis, leading to the adoption of hybrid imaging techniques. Hybrid imaging combines computed tomography (CT) with MPI techniques such as positron emission tomography (PET) and single photon emission computed tomography (SPECT). This integration, often within a single gantry system, enhances the diagnostic accuracy by allowing for attenuation correction (AC), acquisition of the coronary artery calcium score (CACS), and more precise tracing of radiotracer uptake. The built-in CT in modern MPI systems assists in these functions, which is essential for better diagnosis and risk assessment in patients. The addition of CACS to MPI, a method involving the assessment of calcified plaque in coronary arteries, notably enhances diagnostic and prognostic capabilities. CACS helps in identifying atherosclerosis and predicting potential cardiac events, facilitating personalized risk management and the initiation of tailored interventions like statins and aspirin. Such comprehensive imaging strategies not only improve the accuracy of detecting CAD but also help in stratifying patient risk more effectively. In this paper, we discuss how the incorporation of CAC into MPI protocols enhances the diagnostic sensitivity for detecting obstructive CAD, as evidenced by several studies where the addition of CAC to MPI has led to improved outcomes in diagnosing CAD. Moreover, CAC has been shown to unmask silent coronary atherosclerosis in patients with normal MPI results, highlighting its incremental diagnostic value. We will discuss the evolving role of hybrid imaging in guiding therapeutic decisions, particularly the use of statins for cardiovascular prevention. The integration of CAC assessment with MPI not only aids in the early detection and management of CAD but also optimizes therapeutic strategies, enhancing patient care through a more accurate and personalized approach. Such advancements underscore the need for further research to fully establish the benefits of combining CAC with MPI in the clinical assessment of cardiovascular risk.

Phase angle and donor type are determinants of coronary artery calcification in stable kidney transplant recipients at twelve months after transplantation

BACKGROUND AND AIM

Coronary artery calcification (CAC) partially explains the excess cardiovascular morbidity and mortality after kidney transplantation. This study aimed to investigate determinants of CAC in stable kidney transplant recipients at 12 months post-transplantation.

METHODS AND RESULTS

CAC-score was quantified by the Agatston method using non-contrast enhanced computed tomography, and age- and sex-standardized CAC-percentiles were calculated. Univariable and multivariable multinomial logistic regression was performed to study potential determinants of CAC. The independent determinants were included in multivariable multinomial logistic regression adjusting for potential confounders. 203 KTRs (age 54.0 ± 14.7 years, 61.1% male) were included. Participants were categorized into four groups according to CAC percentiles (p = 0 [CAC-score = 0], n = 68; p ≥ 1%-p ≤ 50% [CAC score = 29.0 (4.0-166.0)], n = 31; p > 50 ≤ 75% [CAC score = 101.0 (23.8-348.3)], n = 26; and p>75% [CAC score = 581.0 (148.0-1652)], n = 83). Upon multivariable multinomial logistic regression, patients with a narrower phase angle and patients who had received a graft from a deceased donor had a higher risk of being in the >75th CAC-percentile.

CONCLUSIONS

This study identifies not only metabolic and transplant-related factors, but also phase angle, a composite marker of cell integrity, as an independent determinant of CAC at 12 months after kidney transplantation. This study offers new perspectives for future research into the value of bioelectrical impedance analysis in relation to vascular calcification in kidney transplant recipients.

Imaging biomarkers in cardiac CT: moving beyond simple coronary anatomical assessment

Cardiac computed tomography angiography (CCTA) is considered the standard non-invasive tool to rule-out obstructive coronary artery disease (CAD). Moreover, several imaging biomarkers have been developed on cardiac-CT imaging to assess global CAD severity and atherosclerotic burden, including coronary calcium scoring, the segment involvement score, segment stenosis score and the Leaman-score. Myocardial perfusion imaging enables the diagnosis of myocardial ischemia and microvascular damage, and the CT-based fractional flow reserve quantification allows to evaluate non-invasively hemodynamic impact of the coronary stenosis. The texture and density of the epicardial and perivascular adipose tissue, the hypodense plaque burden, the radiomic phenotyping of coronary plaques or the fat radiomic profile are novel CT imaging features emerging as biomarkers of inflammation and plaque instability, which may implement the risk stratification strategies. The ability to perform myocardial tissue characterization by extracellular volume fraction and radiomic features appears promising in predicting arrhythmogenic risk and cardiovascular events. New imaging biomarkers are expanding the potential of cardiac CT for phenotyping the individual profile of CAD involvement and opening new frontiers for the practice of more personalized medicine.

Computed Tomography-Based Coronary Artery Calcium Score Calculation at a Reduced Tube Voltage Utilizing Iterative Reconstruction and Threshold Modification Techniques: A Feasibility Study

BACKGROUND

The coronary artery calcium score (CACS) indicates cardiovascular health. A concern in this regard is the ionizing radiation from computed tomography (CT). Recent studies have tried to introduce low-dose CT techniques to assess CACS. We aimed to investigate the accuracy of iterative reconstruction (IR) and threshold modification while applying low tube voltage in coronary artery calcium imaging.

METHODS

The study population consisted of 107 patients. Each subject underwent an electrocardiogram-gated CT twice, once with a standard voltage of 120 kVp and then a reduced voltage of 80 kVp. The standard filtered back projection (FBP) reconstruction was applied in both voltages. Considering Hounsfield unit (HU) thresholds other than 130 (150, 170, and 190), CACS was calculated using the FBP-reconstructed 80 kVp images. Moreover, the 80 kVp images were reconstructed utilizing IR at different strength levels. CACS was measured in each set of images. The intraclass correlation coefficient (ICC) was used to compare the CACSs.

RESULTS

A 64% reduction in the effective dose was observed in the 80 kVp protocol compared to the 120 kVp protocol. Excellent agreement existed between CACS at high-level (strength level = 5) IR in low-kVp images and the standard CACS protocol in scores ≥ 11 (ICC > 0.9 and p < 0.05). Increasing the threshold density to 190 HU in FBP-reconstructed low-kVp images yielded excellent agreement with the standard protocol in scores ≥ 11 (ICC > 0.9 and p < 0.05) and good agreement in score zero (ICC = 0.84 and p = 0.02).

CONCLUSIONS

The modification of the density threshold and IR provides an accurate calculation of CACS in low-voltage CT with the potential to decrease patient radiation exposure.

Clinical quantitative coronary artery stenosis and coronary atherosclerosis imaging: a Consensus Statement from the Quantitative Cardiovascular Imaging Study Group

The detection and characterization of coronary artery stenosis and atherosclerosis using imaging tools are key for clinical decision-making in patients with known or suspected coronary artery disease. In this regard, imaging-based quantification can be improved by choosing the most appropriate imaging modality for diagnosis, treatment and procedural planning. In this Consensus Statement, we provide clinical consensus recommendations on the optimal use of different imaging techniques in various patient populations and describe the advances in imaging technology. Clinical consensus recommendations on the appropriateness of each imaging technique for direct coronary artery visualization were derived through a three-step, real-time Delphi process that took place before, during and after the Second International Quantitative Cardiovascular Imaging Meeting in September 2022. According to the Delphi survey answers, CT is the method of choice to rule out obstructive stenosis in patients with an intermediate pre-test probability of coronary artery disease and enables quantitative assessment of coronary plaque with respect to dimensions, composition, location and related risk of future cardiovascular events, whereas MRI facilitates the visualization of coronary plaque and can be used in experienced centres as a radiation-free, second-line option for non-invasive coronary angiography. PET has the greatest potential for quantifying inflammation in coronary plaque but SPECT currently has a limited role in clinical coronary artery stenosis and atherosclerosis imaging. Invasive coronary angiography is the reference standard for stenosis assessment but cannot characterize coronary plaques. Finally, intravascular ultrasonography and optical coherence tomography are the most important invasive imaging modalities for the identification of plaques at high risk of rupture. The recommendations made in this Consensus Statement will help clinicians to choose the most appropriate imaging modality on the basis of the specific clinical scenario, individual patient characteristics and the availability of each imaging modality.

Coronary artery calcium score: we know where we are but not where we may be

Cardiac computed tomography angiography (CCTA) has emerged as a cost-effective and time-saving technique for excluding coronary artery disease. One valuable tool obtained by CCTA is the coronary artery calcium (CAC) score. The use of CAC scoring has shown promise in the risk assessment and stratification of cardiovascular disease. CAC scores can be complemented by plaque analysis to assess vulnerable plaque characteristics and further refine risk assessment. This paper aims to provide a comprehensive understanding of the value of the CAC as a prognostic tool and its implications for patient risk assessment, treatment strategies, and outcomes. CAC scoring has demonstrated superior ability in stratifying patients, especially asymptomatic individuals, compared to traditional risk factors and scoring systems. The main evidence suggests that individuals with a CAC score of 0 have a good long-term prognosis, while an elevated CAC score is associated with increased cardiovascular risk. Finally, the clinical power of CAC scoring and the development of new models for risk stratification could be enhanced by machine learning algorithms.

Automated cardiovascular risk categorization through AI-driven coronary calcium quantification in cardiac PET acquired attenuation correction CT

BACKGROUND

We present an automatic method for coronary artery calcium (CAC) quantification and cardiovascular risk categorization in CT attenuation correction (CTAC) scans acquired at rest and stress during cardiac PET/CT. The method segments CAC according to visual assessment rather than the commonly used CT-number threshold.

METHODS

The method decomposes an image containing CAC into a synthetic image without CAC and an image showing only CAC. Extensive evaluation was performed in a set of 98 patients, each having rest and stress CTAC scans and a dedicated calcium scoring CT (CSCT). Standard manual calcium scoring in CSCT provided the reference standard.

RESULTS

The interscan reproducibility of CAC quantification computed as average absolute relative differences between CTAC and CSCT scan pairs was 75% and 85% at rest and stress using the automatic method compared to 121% and 114% using clinical calcium scoring. Agreement between automatic risk assessment in CTAC and clinical risk categorization in CSCT resulted in linearly weighted kappa of 0.65 compared to 0.40 between CTAC and CSCT using clinically used calcium scoring.

CONCLUSION

The increased interscan reproducibility achieved by our method may allow routine cardiovascular risk assessment in CTAC, potentially relieving the need for dedicated CSCT.

How scan parameter choice affects deep learning-based coronary artery disease assessment from computed tomography

Recently, algorithms capable of assessing the severity of Coronary Artery Disease (CAD) in form of the Coronary Artery Disease-Reporting and Data System (CAD-RADS) grade from Coronary Computed Tomography Angiography (CCTA) scans using Deep Learning (DL) were proposed. Before considering to apply these algorithms in clinical practice, their robustness regarding different commonly used Computed Tomography (CT)-specific image formation parameters-including denoising strength, slab combination, and reconstruction kernel-needs to be evaluated. For this study, we reconstructed a data set of 500 patient CCTA scans under seven image formation parameter configurations. We select one default configuration and evaluate how varying individual parameters impacts the performance and stability of a typical algorithm for automated CAD assessment from CCTA. This algorithm consists of multiple preprocessing and a DL prediction step. We evaluate the influence of the parameter changes on the entire pipeline and additionally on only the DL step by propagating the centerline extraction results of the default configuration to all others. We consider the standard deviation of the CAD severity prediction grade difference between the default and variation configurations to assess the stability w.r.t. parameter changes. For the full pipeline we observe slight instability (± 0.226 CAD-RADS) for all variations. Predictions are more stable with centerlines propagated from the default to the variation configurations (± 0.122 CAD-RADS), especially for differing denoising strengths (± 0.046 CAD-RADS). However, stacking slabs with sharp boundaries instead of mixing slabs in overlapping regions (called true stack ± 0.313 CAD-RADS) and increasing the sharpness of the reconstruction kernel (± 0.150 CAD-RADS) leads to unstable predictions. Regarding the clinically relevant tasks of excluding CAD (called rule-out; AUC default 0.957, min 0.937) and excluding obstructive CAD (called hold-out; AUC default 0.971, min 0.964) the performance remains on a high level for all variations. Concluding, an influence of reconstruction parameters on the predictions is observed. Especially, scans reconstructed with the true stack parameter need to be treated with caution when using a DL-based method. Also, reconstruction kernels which are underrepresented in the training data increase the prediction uncertainty.

Assessing Agreement When Agreement Is Hard to Assess-The Agatston Score for Coronary Calcification

Method comparison studies comprised simple scatterplots of paired measurements, a 45-degree line as benchmark, and correlation coefficients up to the advent of Bland-Altman analysis in the 1980s. The Agatston score for coronary calcification is based on computed tomography of the heart, and it originated in 1990. A peculiarity of the Agatston score is the often-observed skewed distribution in screening populations. As the Agatston score has manifested itself in preventive cardiology, it is of interest to investigate how reproducibility of the Agatston score has been established. This review is based on literature findings indexed in MEDLINE/PubMed before 20 November 2021. Out of 503 identified articles, 49 papers were included in this review. Sample sizes were highly variable (10-9761), the main focus comprised intra- and interrater as well as intra- and interscanner variability assessments. Simple analysis tools such as scatterplots and correlation coefficients were successively supplemented by first difference, later Bland-Altman plots; however, only very few publications were capable of deriving Limits of Agreement that fit the observed data visually in a convincing way. Moreover, several attempts have been made in the recent past to improve the analysis and reporting of method comparison studies. These warrant increased attention in the future.

What should we do about Coronary Calcification on Thoracic CT?

PURPOSE

Coronary artery calcification is a frequent incidental finding on thoracic computed tomography (CT) performed for non-cardiac indications. On electrocardiogram-gated cardiac CT, it is an established marker of coronary artery disease and is associated with increased risk of subsequent cardiac events.

MATERIALS AND METHODS

This review discusses the current evidence and guidelines regarding the reporting of coronary artery calcification on non-electrocardiogram-gated thoracic CT performed for non-cardiac indications.

RESULTS

For patients undergoing routine thoracic CT, coronary artery calcification is associated with an increased risk of myocardial infarction and mortality. Coronary artery calcification can be accurately assessed on non-gated thoracic CT compared to gated CT. Guidelines support the reporting of coronary artery calcification on thoracic CT. However, radiologist opinions vary. The identification of coronary artery calcification on thoracic CT may identify patients with previously unknown coronary artery disease. For asymptomatic patients this may trigger an assessment of modifiable cardiovascular risk factors and guide the appropriate use of preventative medications.

CONCLUSION

Future research will address whether changing management based on calcification on thoracic CT will improve outcomes and automated assessment of calcification using machine learning techniques.

KEY POINTS

· Coronary artery calcification is a frequent incidental finding on thoracic CT.. · The presence and severity of coronary artery calcification is associated with cardiac outcomes and mortality.. · Reporting coronary artery calcification on thoracic CT is supported by national and international guidelines..

CITATION FORMAT

· Williams MC, Llewellyn O, . What Should We Do About Coronary Calcification on Thoracic CT?. Fortschr Röntgenstr 2022; 194: 833 - 840.

Intra-plaque calcium and its relation with the progression of carotid atheromatous disease

BACKGROUND

Calcification and progression of atheromatous disease (AD) both have been independently related with the risk of stroke. However, the link between the two phenomena is still unclear. The main objective of this study was to analyze the temporal evolution of Ca content of carotid atheromatous plaques and its relation with the progression of carotid AD using quantitative CT Angiography (CTA).

METHODS

Forty-three asymptomatic patients with stenosis of the internal carotid artery (ICA)>50% completed the study. Contrast mold volume and calcium (Ca) content by quantitative CTA and Modified Agatston Score (Ca volume x radiological density) were assessed at baseline and after 12±2 months. Biochemical parameters, including main markers of Ca/Phosphorus (P) metabolism, were determined.

RESULTS

CTA measurement showed an increase of volumetric stenosis (volume decrease of the contrast mold), compared to baseline (475.45 (155.6) mm3 x U.H vs 501.3 (171.9) mm3 x U.H; p=0.04) as well as an increase of intra-plaque Ca (64.58 (57.8) mm3x U.H. vs 56.8 (52.3) p=0.002). An inverse correlation between baseline Ca content and volumetric stenosis progression (r= - 0.481; p<0.001), as well as between the increase of carotid Ca and plasma levels of vitamin D (r= 0.4; p=0.025) were also found. Multiple regression analysis found a model with baseline intra-plaque Ca, adjusted by body mass index (BMI) as most predictive of carotid AD progression.

CONCLUSIONS

These results suggest that a higher content of Ca confers greater stability against the progression of carotid AD and, eventually, its ability to generate symptomatology.

Fully Automated Artery-Specific Calcium Scoring Based on Machine Learning in Low-Dose Computed Tomography Screening

PURPOSE

 Evaluation of machine learning-based fully automated artery-specific coronary artery calcium (CAC) scoring software, using semi-automated software as a reference.

METHODS

 A total of 505 patients underwent non-contrast-enhanced calcium scoring computed tomography (CSCT). Automated, machine learning-based software quantified the Agatston score (AS), volume score (VS), and mass score (MS) of each coronary artery [right coronary artery (RCA), left main (LM), circumflex (CX) and left anterior descending (LAD)]. Identified CAC of readers who annotated the data with semi-automated software served as a reference standard. Statistics included comparisons of evaluation time, agreement of identified CAC, and comparisons of the AS, VS, and MS of the reference standard and the fully automated algorithm.

RESULTS

 The machine learning-based software correlated strongly with the reference standard for the AS, VS, and MS (Spearman's rho > 0.969) (p < 0.001), with excellent agreement (ICC > 0.919) (p < 0.001). The mean assessment time of the reference standard was 59 seconds (IQR 39-140) and that of the automated algorithm was 5.9 seconds (IQR 3.9-16) (p < 0.001). The Bland-Altman plots mean difference and 1.96 upper and lower limits of agreement for all arteries combined were: AS 0.996 (1.33 to 0.74), VS 0.995 (1.40 to 0.71), and MS 0.995 (1.35 to 0.74). The mean bias was minimal: 0.964-1.0429. Risk class assignment showed high accuracy for the AS in total (weighed κ = 0.99) and for each individual artery (κ = 0.96-0.99) with corresponding correct risk group assignment in 497 of 505 patients (98.4 %).

CONCLUSION

 The fully automated artery-specific coronary calcium scoring algorithm is a time-saving procedure and shows excellent correlation and agreement compared with the clinically established semi-automated approach.

KEY POINTS

  · Very high correlation and agreement between fully automatic and semi-automatic calcium scoring software.. · Less time-consuming than conventional semi-automatic methods.. · Excellent tool for artery-specific calcium scoring in a clinical setting..

CITATION FORMAT

· Winkelmann MT, Jacoby J, Schwemmer C et al. Fully Automated Artery-Specific Calcium Scoring Based on Machine Learning in Low-Dose Computed Tomography Screening. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1717-2703.

Computed tomography-based calcium scoring in cadaver leg arteries: Influence of dose, reader, and reconstruction algorithm

PURPOSE

Computed tomography (CT) might be a good diagnostic test to accurately quantify calcium in vascular beds but there are multiple factors influencing the quantification. The aim of this study was to investigate the influence of different computed tomography protocol settings in the quantification of calcium in the lower extremities using modified Agatston and volume scores.

METHODS

Fresh-frozen human legs were scanned at different tube current protocols and reconstructed at different slice thickness. Two different iterative reconstruction protocols for conventional CT images were compared. Calcium was manually scored using modified Agatston and volume scores. Outcomes were statistically analyzed using Wilcoxon signed-rank tests and mean absolute and relative differences were plotted in Bland-Altman plots.

RESULTS

Of the 20 legs, 16 had CT detectable calcifications. Differences between thick and thin slice reconstruction protocols were 129 Agatston units and 125% for Agatston and 78.4 mm³ and 57.8% for volume (all p ≤ 0.001). No significant differences were found between low and high tube current protocols. Differences between iDose⁴ and IMR reconstruction protocols for modified Agatston were 34.2 Agatston units and 17.7% and the volume score 33.5 mm³ and 21.2% (all p ≤ 0.001).

CONCLUSIONS

Slice thickness reconstruction and reconstruction method protocols influenced the modified Agatston and volume scores in leg arteries, but tube current and different observers did not have an effect. This data emphasizes the need for standardized quantification of leg artery calcifications. Possible implications are in the development of a more universal quantification method, independent of the type of scan and vasculature.

Reporting incidental coronary, aortic valve and cardiac calcification on non-gated thoracic computed tomography, a consensus statement from the BSCI/BSCCT and BSTI

Incidental coronary and cardiac calcification are frequent findings on non-gated thoracic CT. We recommend that the heart is reviewed on all CT scans where it is visualised. Coronary artery calcification is a marker of coronary artery disease and it is associated with an adverse prognosis on dedicated cardiac imaging and on non-gated thoracic CT performed for non-cardiac indications, both with and without contrast. We recommend that coronary artery calcification is reported on all non-gated thoracic CT using a simple patient-based score (none, mild, moderate, severe). Furthermore, we recommend that reports include recommendations for subsequent management, namely the assessment of modifiable cardiovascular risk factors and, if the patient has chest pain, assessment as per standard guidelines. In most cases, this will not necessitate additional investigations. Incidental aortic valve calcification may also be identified on non-gated thoracic CT and should be reported, along with ancillary findings such as aortic root dilation. Calcification may occur in other parts of the heart including mitral valve/annulus, pericardium and myocardium, but in many cases these are an incidental finding without clinical significance.

HDAC9 is implicated in atherosclerotic aortic calcification and affects vascular smooth muscle cell phenotype

Aortic calcification is an important independent predictor of future cardiovascular events. We performed a genome-wide association meta-analysis to determine SNPs associated with the extent of abdominal aortic calcification (n = 9,417) or descending thoracic aortic calcification (n = 8,422). Two genetic loci, HDAC9 and RAP1GAP, were associated with abdominal aortic calcification at a genome-wide level (P < 5.0 × 10-8). No SNPs were associated with thoracic aortic calcification at the genome-wide threshold. Increased expression of HDAC9 in human aortic smooth muscle cells promoted calcification and reduced contractility, while inhibition of HDAC9 in human aortic smooth muscle cells inhibited calcification and enhanced cell contractility. In matrix Gla protein-deficient mice, a model of human vascular calcification, mice lacking HDAC9 had a 40% reduction in aortic calcification and improved survival. This translational genomic study identifies the first genetic risk locus associated with calcification of the abdominal aorta and describes a previously unknown role for HDAC9 in the development of vascular calcification.

Automated segmentation and quantification of aortic calcification at abdominal CT: application of a deep learning-based algorithm to a longitudinal screening cohort

OBJECTIVE

To investigate an automated aortic calcium segmentation and scoring tool at abdominal CT in an adult screening cohort.

METHODS

Using instance segmentation with convolutional neural networks (Mask R-CNN), a fully automated vascular calcification algorithm was applied to a data set of 9914 non-contrast CT scans from 9032 consecutive asymptomatic adults (mean age, 57.5 ± 7.8 years; 4467 M/5447F) undergoing colonography screening. Follow-up scans were performed in a subset of 866 individuals (mean interval, 5.4 years). Automated abdominal aortic calcium volume, mass, and Agatston score were assessed. In addition, comparison was made with a separate validated semi-automated approach in a subset of 812 cases.

RESULTS

Mean values were significantly higher in males for Agatston score (924.2 ± 2066.2 vs. 564.2 ± 1484.2, p < 0.001), aortic calcium mass (222.2 ± 526.0 mg vs. 144.5 ± 405.4 mg, p < 0.001) and volume (699.4 ± 1552.4 ml vs. 426.9 ± 1115.5 HU, p < 0.001). Overall age-specific Agatston scores increased an average of 10%/year for the entire cohort; males had a larger Agatston score increase between the ages of 40 to 60 than females (91.2% vs. 75.1%, p < 0.001) and had significantly higher mean Agatston scores between ages 50 and 80 (p < 0.001). For the 812-scan subset with both automated and semi-automated methods, median difference in Agatston score was 66.4 with an r² agreement value of 0.84. Among the 866-patient cohort with longitudinal follow-up, the average Agatston score change was 524.1 ± 1317.5 (median 130.9), reflecting a mean increase of 25.5% (median 73.6%).

CONCLUSION

This robust, fully automated abdominal aortic calcification scoring tool allows for both individualized and population-based assessment. Such data could be automatically derived at non-contrast abdominal CT, regardless of the study indication, allowing for opportunistic assessment of cardiovascular risk.

Association of blood levels of marine omega-3 fatty acids with coronary calcification and calcium density in Japanese men

BACKGROUND/OBJECTIVES

Clinical trials of eicosapentaenoic acid (EPA) among high-risk groups in Japan in which consumption of mairne-omega-3 fatty acids (OM3) is much higher than other countries showed slower progression of coronary atherosclerosis. We aimed to determine the cross-sectional associations of coronary artery calcification (CAC) and calcium density with OM3, EPA, and docosahexaenoic acid (DHA), two principal OM3, in the general population in Japan.

SUBJECTS/METHODS

The Shiga Epidemiological Study of Subclinical Atherosclerosis examined a population-based sample of 1074 men aged 40-79 in 2006-08 for computed tomography-measured CAC score (CCS), a well-established biomarker of coronary atherosclerosis, CAC density score (CDS), a potential marker of plaque stabilization, serum levels of OM3, and risk factors.

RESULTS

Prevalence of CCS > 0, ≥ 100, and ≥ 300 was 65.8%, 25.9%, and 12.9%, respectively; the mean (SD) OM3, EPA, and DHA were 10.1% (3.2), 3.2% (1.7), and 5.9% (1.6), respectively. Odds ratios (95% CI, p-value) of CCS 0, 100, and 300 in ordinal logistic regression associated with 1 SD increase of OM3, EPA, and DHA were 0.91 (0.81-1.03, p = 0.12), 0.99 (0.88-1.11, p = 0.87) and 0.84 (0.74-0.94, p = < 0.01), respectively. The inverse association of DHA with CCS remained significant in multivariate-adjusted model: odds ratio of 0.87 (0.77-0.99, p = 0.03). Blood levels of OM3, EPA, or DHA did not have any significant associations with CDS.

CONCLUSIONS

DHA but not EPA had a significant inverse association with coronary atherosclerosis in the general population with high levels of OM3. Future trials are warranted comparing the effect of high-dose DHA and EPA on atherosclerosis and cardiovascular outcomes.

Calcium-binding nanoparticles for vascular disease

Cardiovascular disease (CVD) including atherosclerosis is the leading cause of death worldwide. As CVDs and atherosclerosis develop, plaques begin to form in the blood vessels and become calcified. Calcification within the vasculature and atherosclerotic plaques have been correlated with rupture and consequently, acute myocardial infarction. However, current imaging methods to identify vascular calcification have limitations in determining plaque composition and structure. Nanoparticles can overcome these limitations due to their versatility and ability to incorporate a wide range of targeting and contrast agents. In this review, we summarize the current understanding of calcification in atherosclerosis, their role in instigating plaque instability, and clinical methodologies to detect and analyze vascular calcification. In addition, we highlight the potential of calcium-targeting ligands and nanoparticles to create novel calcium-detecting tools.

The evolving view of coronary artery calcium and cardiovascular disease risk

Calcification of the coronary artery is a complex pathophysiologic process that is intimately associated with atherosclerosis. Extensive investigation has demonstrated the value of identifying and quantifying coronary artery calcium (CAC) in atherosclerotic cardiovascular disease (CVD) prognostication. However, over the last several years, an increasing body of evidence has suggested that CAC has underappreciated aspects that modulate, and at times attenuate, future CVD risk. The most commonly used measure of CAC, the Agatston unit, effectively models both higher density and higher area of CAC as risk factors for future CVD events. Recent findings from the Multi-Ethnic Study of Atherosclerosis (MESA) have challenged this assumption, demonstrating that higher density of CAC is protective for coronary heart disease and CVD events. Statins may be associated with an increase in CAC, an unexpected finding given their clear benefits in the prevention and treatment of CVD. Studies utilizing intracoronary ultrasound and coronary computed tomography angiography have demonstrated that calcified atherosclerotic plaque-as compared with noncalcified or sparsely calcified plaque-is associated with fewer CVD events. These studies lend support to the often-asserted (but as yet unvalidated) view that calcification may play a role in plaque stabilization. Furthermore, vascular calcification, though a surrogate for atherosclerotic plaque burden, may also possess identifiable aspects that can refine CVD risk assessment.

Evaluation of vitamin D levels in relation to coronary CT angiographic findings in an Iranian population

Background

Vitamin D deficiency, as a predisposing factor for coronary artery disease (CAD), is a subject of increasing interest. However, its role as a risk factor has not been proven. This study aimed to investigate the relationship between serum vitamin D levels and CAD.

Materials and methods

Using a cross-sectional design, 180 patients who were candidates for coronary computed tomography angiography (CCTA) were selected. Serum levels of vitamin D were measured and compared with the results of CCTA (including calcium score, and presence and severity of coronary artery involvement due to atherosclerotic plaques).

Results

The mean age of the participants was 60.5±10.6 years and the mean serum vitamin D level was 26.2±15.9 ng/dL (range, 3.5–83.2 ng/dL). Overall, 6.1% of the participants (n=11) had vitamin D deficiency, 56.1% (n=101) had insufficient levels of vitamin D, and 37.8% (n=68) had sufficient levels of vitamin D. The mean serum vitamin D level was significantly lower in patients with severe CAD (P=0.004). The serum vitamin D level in the “positive for CAD” group was 20.98 ng/mL, significantly lower than the level in the “negative for CAD” group (30.47 ng/mL; P<0.001). The mean calcium score among participants was 533.5±87.9. Based on the Spearman test, a significant negative correlation (−0.21) was detected between the serum vitamin D level and coronary artery calcium score (CACS) (P=0.005). Conversely, the mean CACS in the vitamin D deficient group was significantly higher than in the insufficient and sufficient vitamin D groups (P<0.001 for both comparisons).

Conclusion

Vitamin D deficiency was associated with coronary artery calcification and severity of coronary artery stenosis in Iranian patients.

CT calcium scoring. History, current status and outlook

Cardiovascular risk assessment has assumed a prominent role in the course of preventive care of all adults. Traditionally cardiovascular risk assessment has been performed using risk factors including gender, age, smoking history, lipid status, diabetes status, and family history. Increasingly, imaging has been deployed to directly detect coronary atherosclerotic disease. Quantification of coronary calcium (e.g., Agatston method, calcium mass and volume) is readily detected using helical CT scanners. Large multicenter cohort studies have enabled a better understanding of the relevance of coronary calcium detection. The purpose of this review is to review the methods for quantification of coronary artery calcium, as well as to present current and future perspectives on calcium scoring for cardiovascular risk stratification.

Iterative reconstruction can permit the use of lower X-ray tube current in CT coronary artery calcium scoring

OBJECTIVE:

CT coronary artery calcium scoring (CACS) is additive to traditional risk factors for predicting future cardiac events but is associated with relatively high radiation doses. We assessed the feasibility of CACS radiation dose reduction using a lower tube current and iterative reconstruction (IR).

METHODS:

Artificial noise was added to the raw data from 27 CACS studies from patients who were symptomatic to simulate lower tube current scanning (75, 50 and 25% original current). All studies were performed on the same CT scanner at 120 kVp. Data were reconstructed using filtered back projection [Quantum Denoising Software (QDS+)] and IR [adaptive iterative dose reduction three dimensional mild, standard and strong]. Agatston scores were independently measured by two readers. CACS percentile risk scores were calculated.

RESULTS:

At 75, 50 and 25% tube currents, all adaptive iterative dose reduction (AIDR) reconstructions decreased image noise relative to QDS+ (p < 0.05). All AIDR reconstructions resulted in small reductions in Agatston score relative to QDS+ at the standard tube current (p < 0.05). Agatston scores increased with QDS+ at 75, 50 and 25% tube current (p < 0.05), whereas no significant change was observed with AIDR mild at any tested tube current. No difference in the percentile risk score with AIDR mild at any tube current occurred compared with QDS+ at standard tube current (p > 0.05). Interobserver agreement for AIDR mild remained excellent even at 25% tube current (intraclass correlation coefficient 0.997).

CONCLUSION:

Up to 75% reduction in CACS tube current is feasible using AIDR mild.

ADVANCES IN KNOWLEDGE:

AIDR mild IR permits low tube current CACS whilst maintaining excellent intraobserver and interobserver variability and without altering risk classification.

Improving the CAC Score by Addition of Regional Measures of Calcium Distribution: Multi-Ethnic Study of Atherosclerosis

OBJECTIVES

The aim of this study was to investigate whether inclusion of simple measures of calcified plaque distribution might improve the ability of the traditional Agatston coronary artery calcium (CAC) score to predict cardiovascular events.

BACKGROUND

Agatston CAC scoring does not include information on the location and distributional pattern of detectable calcified plaque.

METHODS

We studied 3,262 (50%) individuals with baseline CAC >0 from MESA (Multi-Ethnic Study of Atherosclerosis). Multivessel CAC was defined by the number of coronary vessels with CAC (scored 1 to 4, including the left main). The "diffusivity index" was calculated as: 1 - (CAC in most affected vessel/total CAC), and was used to group participants into concentrated and diffuse CAC patterns. Multivariable Cox proportional hazards regression, area under the curve, and net reclassification improvement analyses were performed for both coronary heart disease (CHD) and cardiovascular disease (CVD) events to assess whether measures of regional CAC distribution add to the traditional Agatston CAC score.

RESULTS

Mean age of the population was 66 ± 10 years, with 42% women. Median follow-up was 10.0 (9.5 to 10.7) years and there were 368 CHD and 493 CVD events during follow-up. Considerable heterogeneity existed between CAC score group and number of vessels with CAC (p < 0.01). Addition of number of vessels with CAC significantly improved capacity to predict CHD and CVD events in survival analysis (hazard ratio: 1.9 to 3.5 for 4-vessel vs. 1-vessel CAC), area under the curve analysis (C-statistic improvement of 0.01 to 0.033), and net reclassification improvement analysis (category-less net reclassification improvement 0.10 to 0.45). Although a diffuse CAC pattern was associated with worse outcomes in participants with ≥2 vessels with CAC (hazard ratio: 1.33 to 1.41; p < 0.05), adding this variable to the Agatston CAC score and number of vessels with CAC did not further improve global risk prediction.

CONCLUSIONS

The number of coronary arteries with calcified plaque, indicating increasingly "diffuse" multivessel subclinical atherosclerosis, adds significantly to the traditional Agatston CAC score for the prediction of CHD and CVD events.

Role of computed tomography screening for detection of coronary artery disease

Coronary artery disease (CAD) is a leading cause of morbidity and mortality in Western populations, and the prediction and prevention of CAD is an inherent challenge facing current health care societies. Computed tomography (CT) has emerged as a noninvasive imaging tool in the field of cardiovascular disease. Notably, CT scanning for detection of coronary artery calcium (CAC) has proven useful in predicting adverse cardiovascular outcomes as well as early identification of CAD. In asymptomatic persons undergoing screening for CAD, CAC is well established as a surrogate of CAD risk and has demonstrated incremental benefit over and above traditional risk prediction tools. In addition, a zero CAC score has shown to reflect a substantially lower risk of CAD and may therefore be considered an important marker of CAD protection. Irrespective of screening in the asymptomatic population, CAC scanning has also displayed a beneficial role in the symptomatic population, specifically as gatekeeper in guiding further treatment decision making. Further still, the combination of alternative CT screening strategies such as CT screening for lung cancer with CAC scanning may hold particular promise as an effective screening approach by lowering overall health costs as well as limiting radiation exposure.

Scoring of coronary artery calcium scans: history, assumptions, current limitations, and future directions

Coronary artery calcium (CAC) scanning is a reliable, noninvasive technique for estimating overall coronary plaque burden and for identifying risk for future cardiac events. Arthur Agatston and Warren Janowitz published the first technique for scoring CAC scans in 1990. Given the lack of available data correlating CAC with burden of coronary atherosclerosis at that time, their scoring algorithm was remarkable, but somewhat arbitrary. Since then, a few other scoring techniques have been proposed for the measurement of CAC including the Volume score and Mass score. Yet despite new data, little in this field has changed in the last 15 years. The main focus of our paper is to review the implications of the current approach to scoring CAC scans in terms of correlation with the central disease - coronary atherosclerosis. We first discuss the methodology of each available scoring system, describing how each of these scores make important indirect assumptions in the way they account (or do not account) for calcium density, location of calcium, spatial distribution of calcium, and microcalcification/emerging calcium that might limit their predictive power. These assumptions require further study in well-designed, large event-driven studies. In general, all of these scores are adequate and are highly correlated with each other. Despite its age, the Agatston score remains the most extensively studied and widely accepted technique in both the clinical and research settings. After discussing CAC scoring in the era of contrast enhanced coronary CT angiography, we discuss suggested potential modifications to current CAC scanning protocols with respect to tube voltage, tube current, and slice thickness which may further improve the value of CAC scoring. We close with a focused discussion of the most important future directions in the field of CAC scoring.

Diagnostic efficacy of vessel specific coronary calcium score in detection of coronary artery stenosis

BACKGROUND

Coronary artery calcification which is determined quantitatively by coronary calcium scoring has been known as a sign of coronary stenosis and thus future cardiac events; hence it has been noticed on spotlight of researchers in recent years. Developing different method for early and optimal detection of coronary artery disease (CAD) is really essential as CAD are the first cause of death in population.

OBJECTIVES

To evaluate predictive value of vessel specific coronary artery calcium (CAC) score in predicting obstructive coronary artery disease.

PATIENTS AND METHODS

In this diagnostic test study we evaluated patients with coronary computed tomography angiography (CCTA) and CAC score which had been referred to two referral radiology center in Tehran, Iran and finally we selected 2525 patients in a single and sequential pattern to create a diagnostic study. The whole-heart CAC scores and vessel specific CAC scores were calculated individually for the 4 major epicardial coronary arteries in 2 distinct group; group A ( patients with previous history of CABG) and group B (patients without history of CABG). For evaluation of obstruction tree cut off points were described: 0 > ; at least 1 segment with any kind of stenosis, ≥ 50; at least 1 segment with stenosis ≥ 50, ≥ 70; at least 1 segment with stenosis ≥ 70.

RESULTS

Mean of coronary calcium scores in terms of each coronary artery vessel increase by increasing coronary stenosis grade in group B; LAD, RCA, LCX respectively have mean CAC score 6.06, 6.21 and 5.04 in normal patients and 221.6, 226.7 and 106.6 in patients with complete stenosis. As expected these findings don't work for group A. Also By increasing calcium score cutoff in all four vessels sensitivity decreased and specificity increased but steal LAD had higher sensitivity than other vessels and LM had higher specificity. Thus using calcium score method is useful for ruling out stenosis in LAD while calcium score of LM can predict existence of stenosis in LM. However none of the vessel specific CAC can reach to 100% sensitivity and specificity of CCTA method.

CONCLUSIONS

CCTA is highly superior than vessel specific CAC score thus to minimize patients radiation does maybe we can eliminate CAC scan as a routinely perform procedure at the beginning of the CCTA.

Medial vascular calcification revisited: review and perspectives

Vascular calcifications (VCs) are actively regulated biological processes associated with crystallization of hydroxyapatite in the extracellular matrix and in cells of the media (VCm) or intima (VCi) of the arterial wall. Both patterns of VC often coincide and occur in patients with type II diabetes, chronic kidney disease, and other less frequent disorders; VCs are also typical in senile degeneration. In this article, we review the current state of knowledge about the pathology, molecular biology, and nosology of VCm, expand on potential mechanisms responsible for poor prognosis, and expose some of the directions for future research in this area.

Can nontriggered thoracic CT be used for coronary artery calcium scoring? A phantom study

PURPOSE

Coronary artery calcium score, traditionally based on electrocardiography (ECG)-triggered computed tomography (CT), predicts cardiovascular risk. However, nontriggered CT is extensively utilized. The study-purpose is to evaluate the in vitro agreement in coronary calcium score between nontriggered thoracic CT and ECG-triggered cardiac CT.

METHODS

Three artificial coronary arteries containing calcifications of different densities (high, medium, and low), and sizes (large, medium, and small), were studied in a moving cardiac phantom. Two 64-detector CT systems were used. The phantom moved at 0-90 mm∕s in nontriggered low-dose CT as index test, and at 0-30 mm∕s in ECG-triggered CT as reference. Differences in calcium scores between nontriggered and ECG-triggered CT were analyzed by t-test and 95% confidence interval. The sensitivity to detect calcification was calculated as the percentage of positive calcium scores.

RESULTS

Overall, calcium scores in nontriggered CT were not significantly different to those in ECG-triggered CT (p>0.05). Calcium scores in nontriggered CT were within the 95% confidence interval of calcium scores in ECG-triggered CT, except predominantly at higher velocities (≥50 mm∕s) for the high-density and large-size calcifications. The sensitivity for a nonzero calcium score was 100% for large calcifications, but 46%±11% for small calcifications in nontriggered CT.

CONCLUSIONS

When performing multiple measurements, good agreement in positive calcium scores is found between nontriggered thoracic and ECG-triggered cardiac CT. Agreement decreases with increasing coronary velocity. From this phantom study, it can be concluded that a high calcium score can be detected by nontriggered CT, and thus, that nontriggered CT likely can identify individuals at high risk of cardiovascular disease. On the other hand, a zero calcium score in nontriggered CT does not reliably exclude coronary calcification.

Coronary artery calcium score: a review

Context

Coronary artery disease (CAD) is the foremost cause of death in many countries and hence, its early diagnosis is usually concerned as a major healthcare priority. Coronary artery calcium scoring (CACS) using either electron beam computed tomography (EBCT) or multislice computed tomography (MSCT) has been applied for more than 20 years to provide an early CAD diagnosis in clinical routine practice. Moreover, its association with other body organs has been a matter of vast research.

Evidence Acquisition

In this review article, techniques of CACS using EBCT and MSCT scanners as well as clinical and research indications of CACS are searched from PubMed, ISI Web of Science, Google Scholar and Scopus databases in a time period between late 1970s through July 2013 and following appropriate selection, dealt with. Moreover, the previous and ongoing research subjects and their results are discussed.

Results

The CACS is vastly applied in early detection of CAD and in many other research fields.

Conclusions

CACS has remarkably changed the screening techniques to detect CAD earlier than before and is generally accepted as a standard of reference for determination of risk of further cardiac events.

Coronary Calcium Scanning in Patients after Adjuvant Radiation for Early Breast Cancer and Ductal Carcinoma In situ

Background and Objective: Radiation therapy (RT) is part of standard adjuvant treatment for breast cancer. Earlier studies demonstrated increased cardiac morbidity and mortality from this. Coronary Calcium scanning utilizing Multidetector Computed Tomography (MDCT) can detect early atherosclerosis in coronary arteries by identifying the amount of calcifications. In our study we employed these tools to detect occult atherosclerosis at least 5 years following breast RT.

Methods: We evaluated 20 asymptomatic patients, <60 years old, treated with RT at least 5 years prior to enrollment. Nine received RT to the left and 11 to the right chest wall. The median interval between RT and calcium scan was 8 years. All patients were treated with external beam RT using tangential technique. All patients underwent MDCT to compute volumetric and Agatston calcium scores of the coronary arteries and the aorta.

Results: Eleven patients had RT to the right chest wall, and eight had a calcium score of 0, while two had minimally elevated scores and one patient had a significantly elevated score. Meanwhile nine patients had RT to the left chest wall, and seven had a calcium score of 0. None had significantly elevated scores. In the aorta, 11 of 20 patients had a score of 0, while 8 of 20 had minimally elevated scores.

Conclusion: In contrast to studies demonstrating increased cardiovascular morbidity, our pilot study did not detect significant occult atherosclerosis using MDCT of the coronaries and aorta of patients assessed five or more years following radiation for treatment of breast cancer.

A phantom study of the effect of heart rate, coronary artery displacement and vessel trajectory on coronary artery calcium score: potential for risk misclassification

BACKGROUND

Accurate coronary artery calcium scoring improves risk stratification in some strata of the population.

OBJECTIVE

We evaluated individual and combined effects of reader experience, heart rate, vessel displacement, and trajectory on computed tomography (CT) Agatston score, calcium volume, and calcium mass in a cardiac phantom model.

METHODS

A cardiac motion phantom was scanned with a 64-slice CT scanner with artificial electrocardiogram gating with combinations of the following: heart rates 60, 80, and 100 beat/min; vessel displacement of 1.25 and 2.5 cm; and multiple vessel trajectories of craniocaudal, right-left, anteroposterior, right coronary artery (RCA), left anterior descending, and left circumflex (LCX). Calcium quantification was done by 2 different readers with the use of 3 methods: Agatston, calcium volume, and calcium mass.

RESULTS

Heart rate, coronary displacement, and trajectory had significant effects on all 3 techniques, with a general decrease in score as the heart rate increased. A vessel displacement of 2.5 cm decreased the Agatston score by 16% (P < 0.0001) and LCX motion decreased the score by 17% (P < 0.0001). Combined effects often resulted in larger differences; for example, a heart rate of 60 beat/min, vessel displacement of 1.25 cm, and RCA motion resulted in an Agatston score of 907, whereas with a heart rate of 100 beat/min, vessel displacement of 2.5 cm, and LCX motion the score was 604.

CONCLUSION

The calcium score is affected by heart rate, vessel displacement, and trajectory.

Coronary artery calcification by computed tomography in epidemiologic research and cardiovascular disease prevention

Both American and European guidelines recommend coronary artery calcification (CAC) as a tool for screening asymptomatic individuals at intermediate risk for coronary heart disease (CHD). These recommendations are based on epidemiologic studies mostly in the United States. We review (1) the use of CAC in primary prevention of CHD in the United States, (2) epidemiologic studies of CAC in asymptomatic adults outside of the United States, and (3) international epidemiologic studies of CAC. This review will not consider clinical studies of CAC among patients or symptomatic individuals. US studies have shown that CAC is a strong independent predictor of CHD in both sexes among middle-aged and old age groups, various ethnic groups, and individuals with and without diabetes and that CAC plays an important role in reclassifying individuals from intermediate to high risk. Studies in Europe support these conclusions. The Electron-Beam Tomography, Risk Factor Assessment Among Japanese and US Men in the Post-World-War-II birth cohort (ERA JUMP) Study is the first international study to compare subclinical atherosclerosis, including CAC among Japanese, Japanese Americans, Koreans, and whites. It showed that as compared with whites, Japanese had lower levels of atherosclerosis, whereas Japanese Americans had similar or higher levels. CAC is being increasingly used as a screening tool for asymptomatic individuals in Europe and the United States. CAC is a powerful research tool, because it enables us to describe differences in atherosclerotic burden across populations. Such research could identify factors responsible for differences among populations, which may improve CHD prevention.

Digital tomosynthesis for aortic arch calcification evaluation: performance comparison with chest radiography with CT as the reference standard

BACKGROUND

Recently developed digital tomosynthesis has shown improved detection of pulmonary lesions with a radiation dose comparable to conventional CR but with a much lower radiation dose than CT.

PURPOSE

To compare the diagnostic performance of digital tomosynthesis (DT) with that of chest radiography (CR) for the detection of aortic arch calcification (AAC).

MATERIAL AND METHODS

The study included 100 patients who underwent multidetector computed tomography (MDCT), DT, and CR (DT and CR were obtained within one week of CT examination). We evaluated and compared the diagnostic performances of DT and CR for the detection of AAC with MDCT as the reference standard. The extent (four grades 0-3) of AAC on DT and CR was also compared with CT calcium score. Inter-observer agreement was analyzed by using kappa statistics.

RESULTS

On DT, overall accuracy for AAC was superior to that of CR (94% and 71%, respectively, P < 0.01). Inter-observer agreement was good with DT and CR (kappa values = 0.74 and 0.62, respectively) for the presence of AAC, and good with DT and moderate with CR (kappa value = 0.64 and 0.53, respectively) for AAC grading. The overall correlation coefficient on AAC grading between DT and CT (calcium score) was superior to that between CR and CT (0.90 and 0.60, respectively).

CONCLUSION

DT is superior to CR for detection and extent evaluation of AAC.

Coronary artery calcium scoring and its impact on the clinical practice in the era of multidetector CT

With the suggestion of coronary artery calcium as an indicator of coronary artery disease 30 years ago, intense and controversial discussion regarding coronary artery calcium has been ongoing. Diverse techniques for evaluation of coronary artery calcium were suggested and validation of its feasibility has been followed up. Following establishment of reference standards, coronary artery calcium became widely utilized in clinical practice and scientific research. Originally coronary artery calcium scoring techniques were developed for prediction of cardiovascular risk. Additionally, coronary artery calcium scoring has been utilized as an indicator for other medical events. Recently, coronary artery calcium scoring used to be applied as a reference standard during scientific research. In this article, the topic of coronary artery calcium, from its introduction to its current usefulness, was discussed from the viewpoints of coronary artery calcium scoring techniques, imaging modalities, validation of the techniques, clinical feasibility of coronary artery calcium scoring beyond traditional cardiovascular risk prediction, and utilization of coronary artery calcium scoring as a reference standard. Popular coronary calcium scoring techniques comprises of Agatston, volume, and mass scores. Through validation of these techniques, pros and cons of each technique were analyzed and proper utility could be suggested. In parallel, the reference standards for Agatston and volume scores were established by age, sex, and race. Through the vigorous controversies, nowadays, the clinical feasibility of coronary artery calcium score as a surrogate marker of cardiovascular risk was acknowledged in the literature.

Noninvasive imaging for assessment of calcification in chronic kidney disease

Vascular calcification is highly prevalent in patients with chronic kidney disease and has a progressive course. Several cardiovascular and uremia-related risk factors, such as abnormalities in mineral metabolism, contribute to the development of vascular calcification, although the pathophysiological mechanisms are still unclear. The presence and extent of vascular calcification is associated with an increased risk of cardiovascular events and mortality. By contrast, patients who do not have calcification seem to have a good prognosis, with minimal or no calcification progression over an extended period of time. A number of noninvasive imaging methods are available to detect vascular calcification and may help clinicians to make therapeutic decisions. Cardiac CT remains the reference standard to detect and quantify coronary artery, aortic and cardiac valve calcification. However, the high cost of equipment, the inability to perform in-office testing and the expertise required limit its use on a routine basis. Other imaging methods, such as planar X-ray, ultrasound and echocardiography, are appropriate alternatives to evaluate vascular and valvular calcification. In this review, we discuss the noninvasive imaging methods most frequently used to assess vascular and valvular calcification, with their advantages and limitations.

A supervised classification-based method for coronary calcium detection in non-contrast CT

Accurate quantification of coronary artery calcium provides an opportunity to assess the extent of atherosclerosis disease. Coronary calcification burden has been reported to be associated with cardiovascular risk. Currently, an observer has to identify the coronary calcifications among a set of candidate regions, obtained by thresholding and connected component labeling, by clicking on them. To relieve the observer of such a labor-intensive task, an automated tool is needed that can detect and quantify the coronary calcifications. However, the diverse and heterogeneous nature of the candidate regions poses a significant challenge. In this paper, we investigate a supervised classification-based approach to distinguish the coronary calcifications from all the candidate regions and propose a two-stage, hierarchical classifier for automated coronary calcium detection. At each stage, we learn an ensemble of classifiers where each classifier is a cost-sensitive learner trained on a distinct asymmetrically sampled data subset. We compute the relative location of the calcifications with respect to a heart-centered coordinate system, and also use the neighboring regions of the calcifications to better characterize their properties for discrimination. Our method detected coronary calcifications with an accuracy, sensitivity and specificity of 98.27, 92.07 and 98.62%, respectively, for a testing dataset of non-contrast computed tomography scans from 105 subjects.

Rationale and approach to evaluation of the impact of medical therapies on progression of atherosclerosis with arterial wall imaging

BACKGROUND

Despite the benefit of medical therapies, there remains a substantial residual risk of cardiovascular events. Atherosclerosis imaging has been used to assess new therapies.

SCOPE

A selective review of current imaging techniques used to evaluate novel anti-atherosclerotic therapies.

FINDINGS

Noninvasive and invasive arterial wall imaging permits characterization of the quantity and composition of atherosclerotic plaque. Serial imaging enables assessment of the impact of therapies on the natural history of disease progression.

CONCLUSION

Both noninvasive and invasive imaging modalities can be used in development programs to provide an early assessment of the impact of novel anti-atherosclerotic agents.

Calcification in atherosclerosis

Coronary calcification has long been known to occur as a part of the atherosclerotic process, although whether it is a marker of plaque stability or instability is still a topic of considerable debate. Coronary calcification is an active process resembling bone formation within the vessel wall and, with the advances in CT technology of the past decade, can be easily quantified and expressed as a coronary artery calcium (CAC) score. The extent of calcium is thought to reflect the total coronary atherosclerotic burden, which has generated interest in using CAC as a marker of risk of cardiovascular events. The current consensus is that large amounts of CAC identify a highly vulnerable patient rather than a vulnerable plaque or vulnerable vessel. Indeed, CAC has incremental prognostic value beyond traditional risk factors in various subsets of the population. Furthermore, whereas the presence of CAC is associated with increased risk, a zero CAC score predicts excellent short-term to mid-term prognosis, even in high-risk patients. The advent of CT angiography has perhaps clouded the importance of CAC as a long-term marker of risk, as opposed to the presence of luminal stenoses that are associated with a more immediate risk of events.