Coronary artery calcium: accuracy and reproducibility of measurements with multi-detector row CT--assessment of effects of different thresholds and quantification methods

Coronary artery calcification burden, atherogenic index of plasma, and risk of adverse cardiovascular events in the general population: evidence from a mediation analysis

BACKGROUND

Dyslipidemia and abnormal cholesterol metabolism are closely related to coronary artery calcification (CAC) and are also critical factors in cardiovascular disease death. In recent years, the atherogenic index of plasma (AIP) has been widely used to evaluate vascular sclerosis. This study aimed to investigate the potential association of AIP between CAC and major adverse cardiovascular events (MACEs).

METHODS

This study included 1,121 participants whose CACs were measured by multislice spiral CT. Participants' CAC Agatston score, CAC mass, CAC volume, and number of vessels with CACs were assessed. AIP is defined as the base 10 logarithm of the ratio of triglyceride (TG) concentration to high-density lipoprotein-cholesterol (HDL-C) concentration. We investigated the multivariate-adjusted associations between AIP, CAC, and MACEs. The mediating role of the AIP in CAC and MACEs was subsequently discussed.

RESULTS

During a median follow-up of 31 months, 74 MACEs were identified. For each additional unit of log-converted CAC, the MACE risk increased by 48% (HR 1.48 [95% CI 1.32-1.65]). For each additional unit of the AIP (multiplied by 10), the MACEs risk increased by 19%. Causal mediation analysis revealed that the AIP played a partial mediating role between CAC (CAC Agatston score, CAC mass) and MACEs, and the mediating proportions were 8.16% and 16.5%, respectively. However, the mediating effect of CAC volume tended to be nonsignificant (P = 0.137).

CONCLUSIONS

An increased AIP can be a risk factor for CAC and MACEs. Biomarkers based on lipid ratios are a readily available and low-cost strategy for identifying MACEs and mediating the association between CAC and MACEs. These findings provide a new perspective on CAC treatment, early diagnosis, and prevention of MACEs.

Accuracy of aortic valve calcification volume score for identification of significant aortic stenosis on non-electrocardiographic-gated computed tomography compared to the Agatston scoring system

BACKGROUND

Considering the absence of reports validating the precision of the volume score and the relationship between the volume and Agatston scores, this study evaluated the accuracy of the volume score compared to the Agatston score for the quantitative measurement of aortic valve calcification (AVC) on non-electrocardiographic-gated computed tomography (CT).

METHODS

We retrospectively analysed the AVC scores of 5385 patients who underwent transthoracic echocardiography between March 1, 2013 and December 26, 2019 ​at our institution, using non-contrast non-electrocardiographic-gated CT. The thresholds for significant aortic stenosis (AS) were computed using receiver operating characteristic curves based on the AVC scores. The area under the curve (AUC) of the Agatston and volume scores for significant AS were compared to evaluate the accuracy of the scoring method.

RESULTS

All sex-specific AVC thresholds of the volume score for significant AS (moderate and high AS severity, moderate and high AS severity without discordance, discordant severe AS, and concordant severe AS) showed high sensitivity and specificity (AUC, 0.978-0.996; sensitivity, 94.2-98.4%; specificity, 90.1-100%). No significant differences in the AUC were observed between the Agatston and volume scores for significant AS in male and female patients.

CONCLUSION

All volume score threshold values showed high sensitivity and specificity for identifying significant AS. The accuracy of the test for AVC thresholds of the volume score for significant AS was comparable to that of the Agatston score. Our findings raise questions about the significance of weighting calcium density in the Agatston score for assessing AS severity.

Performance of calcium quantifications on low-dose photon-counting detector CT with high-pitch: A phantom study

Purpose

To evaluate the performance of calcium quantification on photon-counting detector CT (PCD-CT) with high-pitch at low radiation doses compared to third-generation dual-source energy-integrating detector CT (EID-CT).

Materials and methods

The phantom with three calcium inserts (50, 100, and 300 mg of calcium per milliliter), with and without the elliptical outer layer, was evaluated using high-pitch (3.2) and standard pitch (0.8) on PCD-CT, and standard pitch on EID-CT. Scans were performed with different tube voltages (PCD-CT: 120 and 140 kilo-voltage peak [kVp]; EID-CT: 70/Sn150 and 100/Sn150 kVp) and four radiation doses (1, 3, 5, and, 10 milli-Gray [mGy]). Utilizing the true calcium concentrations (CCtrue) of the phantom as the gold standard references, regression equations for each kVp setting were formulated to convert CT attenuations (CaCT) into measured calcium concentrations (CCm). The correlation analysis between CaCT and CCtrue was performed. The percentage absolute bias (PAB) was calculated from the differences between CCm and CCtrue and used to analyze the effects of scanning parameters on calcium quantification accuracy.

Results

A strong correlation was found between CaCT and CCtrue on PCD-CT (r > 0.99) and EID-CT (r > 0.98). For high- and standard-pitch scans on PCD-CT, the accuracy of calcium quantification is comparable (p = 0.615): the median (interquartile range [IQR]) of PAB was 5.59% (2.79%-8.31%) and 4.87 % (2.62%-8.01%), respectively. The PAB median (IQR) was 7.43% (3.77%-11.75%) for EID-CT. The calcium quantification accuracy of PCD-CT is superior to EID-CT at the large phantom (5.46% [2.68%-9.55%] versus 9.01% [6.22%-12.74%]), and at the radiation dose of 1 mGy (4.43% [2.08%-8.59%] versus 13.89% [8.93%-23.09%]) and 3 mGy (4.61% [2.75%-6.51%] versus 9.97% [5.17%-14.41%]), all p < 0.001.

Conclusions

Calcium quantification using low-dose PCD-CT with high-pitch scanning is feasible and accurate, and superior to EID-CT.

CT-derived coronary artery calcium density is affected by regional lesion distribution and image reconstruction parameters

PURPOSE

The prognostic relevance of coronary artery calcium (CAC) density, assessed from cardiac CT scans, is established. However, the influence of CAC distribution, volume, image reconstruction, and clinical factors on CAC density warrants further examination.

METHODS

In this study, 120 patients underwent non-contrast ECG-gated cardiac CT scans using a prospectively defined CAC scoring protocol with 1-, 3-, and 5-mm thick image reconstructions, both with and without a 20% image overlap. We segmented CAC in all reconstructions and assessed the relationship between CAC density, volume, and number of detected calcifications/patient.

RESULTS

Overall, 75/120 (63%) patients (66% men, mean age 63 ± 11 years) presented CAC across 342 segments. CAC density, CAC volume, and the number of detected calcifications decreased with increasing slice thickness (p < 0.001 for all); these effects were slightly reduced by image overlap (p < 0.001 for all). Higher CAC density correlated with greater CAC volume (ρ = 0.62; p < 0.001) and more calcified segments per person (ρ = 0.32; p = 0.006). Higher CAC density was also associated with lower patient weight (beta: -0.6, 95%CI: -1.1--0.1, p = 0.022) and increased high-density lipoprotein (HDL) levels (beta: 0.7, 95%CI: 0.0-1.4, p = 0.046). In a multivariable analysis adjusted for clinical covariates, lower CAC density was associated with broader CAC distribution (i.e., a higher number of calcified segments at a given CAC volume; beta-coefficient: -58.9; 95%CI: -84.7 to -33.1; p < 0.001).

CONCLUSION

CAC density is significantly impacted by regional CAC distribution and image reconstruction, potentially confounding its prognostic value. Accounting for these factors may improve patient risk assessment, management, and cardiovascular health outcomes.

Impact of Cardiac Motion on coronary artery calcium scoring using a virtual non-iodine algorithm on photon-counting detector CT: a dynamic phantom study

This study assessed the impact of cardiac motion and in-vessel attenuation on coronary artery calcium (CAC) scoring using virtual non-iodine (VNI) against virtual non-contrast (VNC) reconstructions on photon-counting detector CT. Two artificial vessels containing calcifications and different in-vessel attenuations (500, 800HU) were scanned without (static) and with cardiac motion (60, 80, 100 beats per minute [bpm]). Images were post-processed using a VNC and VNI algorithm at 70 keV and quantum iterative reconstruction (QIR) strength 2. Calcium mass, Agatston scores, cardiac motion susceptibility (CMS)-indices were compared to physical mass, static scores as well as between reconstructions, heart rates and in-vessel attenuations. VNI scores decreased with rising heart rate (p < 0.01) and showed less underestimation than VNC scores (p < 0.001). Only VNI scores were similar to the physical mass at static measurements, and to static scores at 60 bpm. Agatston scores using VNI were similar to static scores at 60 and 80 bpm. Standard deviation of CMS-indices was lower for VNI-based than for VNC-based CAC scoring. VNI scores were higher at 500 than 800HU (p < 0.001) and higher than VNC scores (p < 0.001) with VNI scores at 500 HU showing the lowest deviation from the physical reference. VNI-based CAC quantification is influenced by cardiac motion and in-vessel attenuation, but least when measuring Agatston scores, where it outperforms VNC-based CAC scoring.

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.

The Correlation between the Vascular Calcification Score of the Coronary Artery and the Abdominal Aorta in Patients with Psoriasis

Psoriasis is known as an independent risk factor for cardiovascular disease due to its chronic inflammation. Studies have been conducted to evaluate the progress of atherosclerotic plaques in psoriasis. However, inadequate efforts have been made to clarify the relationship between atherosclerosis progress in coronary arteries and other important blood vessels. For that reason, we investigated the correlation and development of the coronary artery calcification score (CACS) and the abdominal aortic calcification score (AACS) during a follow-up examination. Eighty-three patients with psoriasis underwent coronary computed tomography angiography (CCTA) for total CACS and abdominal computed tomography (AbCT) for total AACS. PASI score, other clinical features, and blood samples were collected at the same time. The patients' medical histories were also retrieved for further analysis. Linear regression was used to analyze the CACS and AACS associations. There was a moderate correlation between CACS and AACS, while both calcification scores relatively reflected the coronary plaque number, coronary stenosis number, and stenosis severity observed with CCTA. Both calcification scores were independent of the PASI score. However, a significantly higher CACS was found in psoriatic arthritis, whereas no similar phenomenon was recorded for AACS. To conclude, both CACS and AACS might be potential alternative tests to predict the presence of coronary lesions as confirmed by CCTA.

Coronary Artery Calcium Data and Reporting System (CAC-DRS): A Primer

The Coronary Artery Calcium Data and Reporting System (CAC-DRS) is a standardized reporting method for calcium scoring on computed tomography. CAC-DRS is applied on a per-patient basis and represents the total calcium score with the number of vessels involved. There are 4 risk categories ranging from CAC-DRS 0 to CAC-DRS 3. CAC-DRS also provides risk prediction and treatment recommendations for each category. The main strengths of CAC-DRS include a detailed and meaningful representation of CAC, improved communication between physicians, risk stratification, appropriate treatment recommendations, and uniform data collection, which provides a framework for education and research. The major limitations of CAC-DRS include a few missing components, an overly simple visual approach without any standard reference, and treatment recommendations lacking a basis in clinical trials. This consistent yet straightforward method has the potential to systemize CAC scoring in both gated and non-gated scans.

Targeting a Silent Disease: Vascular Calcification in Chronic Kidney Disease

Chronic kidney disease (CKD) patients have a higher risk of developing early cardiovascular disease (CVD). Although vascular calcification (VC) is one of the strongest predictors of CVD risk, its diagnosis among the CKD population remains a serious clinical challenge. This is mainly due to the complexity of VC, which results from various interconnected pathological mechanisms occurring at early stages and at multiples sites, affecting the medial and intimal layers of the vascular tree. Here, we review the most used and recently developed imaging techniques, here referred to as imaging biomarkers, for VC detection and monitoring, while discussing their strengths and limitations considering the specificities of VC in a CKD context. Although imaging biomarkers have a crucial role in the diagnosis of VC, with important insights into CVD risk, circulating biomarkers represent an added value by reflecting the molecular dynamics and mechanisms involved in VC pathophysiological pathways, opening new avenues into the early detection and targeted interventions. We propose that a combined strategy using imaging and circulating biomarkers with a role in multiple VC molecular mechanisms, such as Fetuin-A, Matrix Gla protein, Gla-rich protein and calciprotein particles, should represent high prognostic value for management of CVD risk in the CKD population.

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.

Generative models for reproducible coronary calcium scoring

Purpose: Coronary artery calcium (CAC) score, i.e., the amount of CAC quantified in CT, is a strong and independent predictor of coronary heart disease (CHD) events. However, CAC scoring suffers from limited interscan reproducibility, which is mainly due to the clinical definition requiring application of a fixed intensity level threshold for segmentation of calcifications. This limitation is especially pronounced in non-electrocardiogram-synchronized computed tomography (CT) where lesions are more impacted by cardiac motion and partial volume effects. Therefore, we propose a CAC quantification method that does not require a threshold for segmentation of CAC. Approach: Our method utilizes a generative adversarial network (GAN) where a CT with CAC is decomposed into an image without CAC and an image showing only CAC. The method, using a cycle-consistent GAN, was trained using 626 low-dose chest CTs and 514 radiotherapy treatment planning (RTP) CTs. Interscan reproducibility was compared to clinical calcium scoring in RTP CTs of 1662 patients, each having two scans. Results: A lower relative interscan difference in CAC mass was achieved by the proposed method: 47% compared to 89% manual clinical calcium scoring. The intraclass correlation coefficient of Agatston scores was 0.96 for the proposed method compared to 0.91 for automatic clinical calcium scoring. Conclusions: The increased interscan reproducibility achieved by our method may lead to increased reliability of CHD risk categorization and improved accuracy of CHD event prediction.

Deep learning for vessel-specific coronary artery calcium scoring: validation on a multi-centre dataset

AIMS

To present and validate a fully automated, deep learning (DL)-based branch-wise coronary artery calcium (CAC) scoring algorithm on a multi-centre dataset.

METHODS AND RESULTS

We retrospectively included 1171 patients referred for a CAC computed tomography examination. Total CAC scores for each case were manually evaluated by a human reader. Next, each dataset was fully automatically evaluated by the DL-based software solution with output of the total CAC score and sub-scores per coronary artery (CA) branch [right coronary artery (RCA), left main (LM), left anterior descending (LAD), and circumflex (CX)]. Three readers independently manually scored the CAC for all CA branches for 300 cases from a single centre and formed the consensus using a majority vote rule, serving as the reference standard. Established CAC cut-offs for the total Agatston score were used for risk group assignments. The performance of the algorithm was evaluated using metrics for risk class assignment based on total Agatston score, and unweighted Cohen's Kappa for branch label assignment. The DL-based software solution yielded a class accuracy of 93% (1085/1171) with a sensitivity, specificity, and accuracy of detecting non-zero coronary calcium being 97%, 93%, and 95%. The overall accuracy of the algorithm for branch label classification was 94% (LM: 89%, LAD: 91%, CX: 93%, RCA: 100%) with a Cohen's kappa of k = 0.91.

CONCLUSION

Our results demonstrate that fully automated total and vessel-specific CAC scoring is feasible using a DL-based algorithm. There was a high agreement with the manually assessed total CAC from a multi-centre dataset and the vessel-specific scoring demonstrated consistent and reproducible results.

An Analytic Method for Calculating Scanner-, Kilovoltage Peak-, and Patient Size-Specific Hounsfield Unit Scale Thresholds for Agatston Score

OBJECTIVE

This study aimed to calculate scanner-, kilovoltage peak (kVp)-, and patient size-specific computed tomography (CT) number thresholds for determining Agatston score (AgSc).

METHODS

The proposed method was validated using calcium measurements in an anthropomorphic phantom for 4 CT scanners made by 4 vendors. The derived mass concentration (γ) thresholds were used to calculate kVp- and patient size-specific CT number thresholds. Two models were applied to reduce intrascanner and interscanner AgSc variation, respectively.

RESULTS

The mean error of the modeled CT numbers is 1.8% (0.1%-4.4%). Model 1 has comparable results to the published phantom calibration method for an average-size patient (error, 1.5%; 0.1%-5.1%). The size- and the kVp-dependent fitting of modeled results have R2 greater than 0.965.

CONCLUSIONS

Our results show a potential to enable accurate determination of AgSc under diverse conditions (eg, reduced tube potential) and are more easily applicable to different patient sizes than the phantom calibration method.

Quantification of Calcium in Peripheral Arteries of the Lower Extremities: Comparison of Different CT Scanners and Scoring Platforms

OBJECTIVES

The aim of this study was to investigate the interscanner and interscoring platform variability of calcium quantification in peripheral arteries of the lower extremities.

MATERIALS AND METHODS

Twenty human fresh-frozen legs were scanned using 3 different computed tomography (CT) scanners. The radiation dose (CTDIvol) was kept similar for all scanners. The calcium scores (Agatston and volume scores) were quantified using 4 semiautomatic scoring platforms. Comparative analysis of the calcium scores between scanners and scoring platforms was performed by using the Friedman test; post hoc analysis was performed by using the Wilcoxon signed rank test with Bonferroni correction.

RESULTS

Sixteen legs had calcifications and were used for data analysis. Agatston and volume scores ranged from 12.1 to 6580 Agatston units and 18.2 to 5579 mm3. Calcium scores differed significantly between Philips IQon and Philips Brilliance 64 (Agatston: 19.5% [P = 0.001]; volume: 14.5% [P = 0.001]) and Siemens Somatom Force (Agatston: 18.1% [P = 0.001]; volume: 17.5% [P = 0.001]). The difference between Brilliance 64 and Somatom Force was smaller (Agatston: 5.6% [P = 0.778]; volume: 7.7% [P = 0.003]). With respect to the interscoring platform variability, OsiriX produced significantly different Agatston scores compared with the other 3 scoring platforms (OsiriX vs IntelliSpace: 14.8% [P = 0.001] vs Syngo CaScore: 13.9% [P = 0.001] vs iX viewer: 13.2% [P < 0.001]). For the volume score, the differences between all scoring platforms were small ranging from 2.9% to 4.0%. Post hoc analysis showed a significant difference between OsiriX and IntelliSpace (3.8% [P = 0.001]).

CONCLUSIONS

The use of different CT scanners resulted in notably different Agatston and volume scores, whereas the use of different scoring platforms resulted in limited variability especially for the volume score. In conclusion, the variability in calcium quantification was most evident between different CT scanners and for the Agatston score.

Automated coronary artery calcium scoring using nested U-Net and focal loss

Coronary artery calcium (CAC) is a great risk predictor of the atherosclerotic cardiovascular disease and CAC scores can be used to stratify the risk of heart disease. Current clinical analysis of CAC is performed using onsite semiautomated software. This semiautomated CAC analysis requires experienced radiologists and radiologic technologists and is both demanding and time-consuming. The purpose of this study is to develop a fully automated CAC detection model that can quantify CAC scores. A total of 1,811 cases of cardiac examinations involving contrast-free multidetector computed tomography were retrospectively collected. We divided the database into the Training Data Set, Validation Data Set, Testing Data Set 1, and Testing Data Set 2. The Training, Validation, and Testing Data Set 1 contained cases with clinically detected CAC; Testing Data Set 2 contained those without detected calcium. The intraclass correlation coefficients between the overall standard and model-predicted scores were 1.00 for both the Training Data Set and Testing Data Set 1. In Testing Data Set 2, the model was able to detect clinically undetected cases of mild calcium. The results suggested that the proposed model’s automated detection of CAC was highly consistent with clinical semiautomated CAC analysis. The proposed model demonstrated potential for clinical applications that can improve the quality of CAC risk stratification.

The ratio of the max-to-mean coronary artery calcium score in the most calcified vessel is associated with the presence of coronary artery disease

PURPOSE

This study aimed to clarify the relationship between the severity of the calcium burden in the most calcified coronary vessel and coronary artery disease (CAD).

METHOD

Of 2150 patients, 376 examined by both coronary computed tomographic angiography and invasive coronary angiography (ICA) within 30 days at Sun Yat-sen Memorial Hospital between March 2011 and July 2020 were included. Three coronary artery calcium scores (CACSs), including the Agatston score, volume score, and mass score, and other clinical variables were recorded. The ratio of max-to-mean CACS in the most calcified vessel (CACS_max:mean) was defined as the CACS in the most calcified vessel/average CACS of the four major epicardial coronary arteries. Logistic regression and least absolute shrinkage and selection operator (LASSO) analyses were performed to assess the relationship between CACS_max:mean and CAD.

RESULTS

CACS_max:mean was higher in 81.1% of subjects diagnosed with CAD than in subjects without CAD. In multivariate logistic regression analysis, CACS_max:mean determined by the Agatston score, volumetric score, and mass score was associated with CAD. In LASSO analysis, Agatston score_max:mean (not the total Agatston score or other CACS_max:mean) had the strongest correlation with CAD (β = 0.125). AUCs in the training set and the validation set were 0.811 and 0.789, respectively. Increased age, diabetes and hypertension correlated with higher Agatston score_max:mean.

CONCLUSIONS

In addition to total CACS, CACS_max:mean may be a novel diagnostic parameter for CAD, showing the calcium burden severity.

Coronary artery calcium progression after coronary artery bypass grafting surgery

OBJECTIVES

Accelerated atherosclerosis is a well-established phenomenon after coronary artery bypass grafting surgery (CABG). In this study, we analysed coronary artery calcium (CCS) progression after CABG.

METHODS

We retrospectively measured the CCS Agatston score (AS), volume score (VS) and mass score (MS) of 39 patients before and after CABG. The annualised CCS change and annualised CCS percent change of each coronary artery, coronary artery segments proximal and distal to anastomosis were analysed.

RESULTS

Mean age at the time of the surgery was 59.8±8.5 years. Follow-up period between the first and second CT scans was 6.7±2.8 (range, 1.1-12.8) years. Annualised CCS percent change (AS, VS and MS) of the coronary segments proximal-to-anastomosis did not differ from that of the non-grafted coronary arteries as follow: segments proximal-to-anastomosis: median (Q1-Q3) 12.8 (5.0-37.4), 13.7 (6.1-41.1) and 14.9 (5.4-53.7), left main coronary artery 12.6 (7.4-43.8), 22.0 (8.1-44.4) and 18.2 (7.3-57.4), non-grafted left circumflex artery: 13.5 (4.4-38.1), 10.5 (2.9-45.2) and 11.5 (7.1-47.9) and non-grafted right coronary artery: 31.4 (14.4-74.5), 25.2 (16.7-62.0) and 31.3 (23.8-85.6), respectively. Likewise, annualised percent change (AS, VS and MS) was similar between the native coronary arteries. Multivariate regression analysis showed that diabetes mellitus was the only predictor of annualised percent progression of the total CCS of >15% (HR, 8.12; 95% CI, 1.05 to 26.6; p=0.04).

CONCLUSION

The CCS post-CABG did not follow an accelerated progression process. Among coronary artery disease risk factors, diabetes mellitus is the only predictor of annualised CCS percent progression of >15% post-CABG.

Evaluating a calcium-aware kernel for CT CAC scoring with varying surrounding materials and heart rates: a dynamic phantom study

OBJECTIVES

The purpose of this study was twofold. First, the influence of a novel calcium-aware (Ca-aware) computed tomography (CT) reconstruction technique on coronary artery calcium (CAC) scores surrounded by a variety of tissues was assessed. Second, the performance of the Ca-aware reconstruction technique on moving CAC was evaluated with a dynamic phantom.

METHODS

An artificial coronary artery, containing two CAC of equal size and different densities (196 ± 3, 380 ± 2 mg hydroxyapatite cm^-3), was moved in the center compartment of an anthropomorphic thorax phantom at different heart rates. The center compartment was filled with mixtures, which resembled fat, water, and soft tissue equivalent CT numbers. Raw data was acquired with a routine clinical CAC protocol, at 120 peak kilovolt (kVp). Subsequently, reduced tube voltage (100 kVp) and tin-filtration (150Sn kVp) acquisitions were performed. Raw data was reconstructed with a standard and a novel Ca-aware reconstruction technique. Agatston scores of all reconstructions were compared with the reference (120 kVp) and standard reconstruction technique, with relevant deviations defined as > 10%.

RESULTS

For all heart rates, Agatston scores for CAC submerged in fat were comparable to the reference, for the reduced-kVp acquisition with Ca-aware reconstruction kernel. For water and soft tissue, medium-density Agatston scores were again comparable to the reference for all heart rates. Low-density Agatston scores showed relevant deviations, up to 15% and 23% for water and soft tissue, respectively.

CONCLUSION

CT CAC scoring with varying surrounding materials and heart rates is feasible at patient-specific tube voltages with the novel Ca-aware reconstruction technique.

KEY POINTS

• A dedicated calcium-aware reconstruction kernel results in similar Agatston scores for CAC surrounded by fatty materials regardless of CAC density and heart rate. • Application of a dedicated calcium-aware reconstruction kernel allows for radiation dose reduction. • Mass scores determined with CT underestimated physical mass.

Technical Note: kV-independent coronary calcium scoring: A phantom evaluation of score accuracy and potential radiation dose reduction

PURPOSE

To determine the accuracy of CT number and calcium score of a kV-independent technique based on an artificial 120 kV reconstruction, and its potential to reduce radiation dose.

METHODS

Anthropomorphic chest phantoms were scanned on a third-generation dual-source CT system equipped with the artificial 120 kV reconstruction. First, a phantom module containing a 20-mm diameter hydroxyapatite (HA) insert was scanned inside the chest phantoms at different tube potentials (70-140 kV) to evaluate calcium CT number accuracy. Next, three small HA inserts (diameter/length = 5 mm) were inserted into a pork steak and scanned inside the phantoms to evaluate calcium score accuracy at different kVs. Finally, the same setup was scanned using automatic exposure control (AEC) at 120 kV, and then with automatic kV selection (auto-kV). Phantoms were also scanned at 120 kV using a size-dependent mA chart. CT numbers of soft tissue and calcium were measured from different kV images. Calcium score of each small HA insert was measured using commercial software.

RESULTS

The CT number difference from 120 kV was small with tube potentials from 90 to 140 kV for both soft tissue and calcium (maximal difference of 4/5 HU, respectively). Consistent calcium scores were obtained from images of different kVs compared to 120 kV, with a relative difference <8%. Auto-kV provided a 25-34% dose reduction compared to AEC alone.

CONCLUSION

A kV-independent calcium scoring technique can produce artificial 120 kV images with consistent soft tissue and calcium CT numbers compared to standard 120 kV examinations. When coupled with auto-kV, this technique can reduce radiation by 25-34% compared to that with AEC alone, while providing consistent calcium scores as that of standard 120 kV examinations.

Association of Plasma MiRNA-204 and the Presence and Severity of Coronary Artery Calcification in Patients With Type 2 Diabetes

We investigated the association between plasma microRNA (miR)-204 and coronary artery calcification (CAC) in patients with type 2 diabetes mellitus (T2DM). We consecutively enrolled 179 individuals with T2DM who underwent coronary computed tomography at Anzhen Hospital from January 2015 to September 2016. The CAC score (CACS) was expressed in Agatston units and >10 Hounsfield units were defined as CAC-positive status. Significant CAC was observed in 98 (54.7%) patients. Plasma miR-204 levels (relative expression) were significantly lower in patients with significant CAC than controls (1.001 ± 0.100 vs 0.634 ± 0.211, P < .001). Plasma miR-204 levels were also negatively correlated with the glycosylated hemoglobin A_1c (HbA_1c) level (r = -0.702, P < .001), CACS (r = -0.710, P < .001), and the United Kingdom Prospective Diabetes Study (UKPDS) score (r = -0.355, P < .001). After multivariate logistic analyses, plasma miR-204 levels were still significantly and independently associated with the presence of CAC (odds ratio = 0.103, CI = 0.018-0.583, P < .001) after adjustment for conventional risk factors. Receiver operating characteristic curve analysis showed that plasma miR-204 levels can predict the severity and extent of CAC, and the specificity was higher than that of the traditional risk factors UKPDS score and HbA_1c. In conclusion, the downregulation of miR-204 was independently associated with CAC in patients with T2DM.

Statin effect on coronary calcium distribution, mass and volume scores and associations with immune activation among HIV+ persons on antiretroviral therapy

BACKGROUND

Inflammation has been associated with whole heart coronary artery calcification (CAC) among people with HIV (PWH) on antiretroviral therapy (ART); however, prior studies have not evaluated the distribution of calcium or separated mass versus volume scores, which are differentially associated with clinical events in the general population. Statins may also have a greater effect on CAC mass compared with volume.

METHODS

147 PWH were randomized 1:1 to rosuvastatin 10 mg or placebo and followed for 96 weeks. We re-analysed coronary calcium scans from 0, 48 and 96 weeks to determine mass and volume scores and measures of CAC diffusivity. Mixed effects models and generalized estimating equations were used to examine longitudinal associations of CAC with treatment and biomarkers.

RESULTS

Median age at study entry was 46 years; 78% were male and 68% African American. Median CD4+ was 613 and half were on protease inhibitors. Randomization to statin therapy was not associated with a change in mass score, volume score, number of involved vessels or diffusivity index (all P>0.1). Soluble CD14 was associated with the presence of CAC (P=0.05) and borderline associated with number of involved vessels (P=0.07) across all three time points.

CONCLUSIONS

In PWH on ART, moderate intensity rosuvastatin does not appear to have a significant effect on volume, mass or regional distribution of CAC over 96 weeks. We extend previous cross-sectional observations to show that soluble CD14 is associated with whole heart CAC over time and independently of age and systolic blood pressure.

Measurement of coronary artery calcium volume using ultra-high-resolution computed tomography: A preliminary phantom and cadaver study

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Small calcifications were moe accurately detectable on SHR- than NR images.

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The mean CAC volume was significantly higher on SHR- than NR images of the cadavers.

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SHR imaging may facilitate the accurate quantification of the CAC.

Objectives

In this phantom- and cadaver study we investigated the differences of coronary artery calcium (CAC) volume on ultra-high-resolution computed tomography (U-HRCT) scans and conventional CT.

Methods

We scanned a coronary calcium phantom and the coronary arteries of five cadavers using U-HRCT in normal- and super-high resolution (NR, SHR) mode. The NR mode was similar to conventional CT; 896 detector channels, a matrix size of 512, and a slice thickness of 0.5 mm were applied. In SHR mode, we used 1792 detector channels, a matrix size of 1024, and a slice thickness of 0.25 mm. The CAC volume on NR- and SHR images were recorded. Differences in the physical- and the calculated CAC volume were defined as the error value and compared between NR- and SHR images of the phantom. Differences between the CAC volume on NR- and SHR scans of the cadavers were also recorded.

Results

The mean error value was lower on SHR- than NR images of the phantom (14.0 %, SD 11.1 vs 20.1 %, SD 15.2, p = 0.01). The mean CAC volume was significantly higher on SHR- than NR images of the cadavers (153.4 mm³, SD 161.0 vs 144.7 mm³, SD 164.8, p < 0.01).

Conclusions

As small calcifications were more clearly visualized on U-HRCT images in SHR mode than on conventional (NR) CT scans, SHR imaging may facilitate the accurate quantification of the CAC.

Prognostic significance of subtle coronary calcification in patients with zero coronary artery calcium score: From the CONFIRM registry

BACKGROUND AND AIMS

The Agatston coronary artery calcium score (CACS) may fail to identify small or less dense coronary calcification that can be detected on coronary CT angiography (CCTA). We investigated the prevalence and prognostic importance of subtle calcified plaques on CCTA among individuals with CACS 0.

METHODS

From the prospective multicenter CONFIRM registry, we evaluated patients without known CAD who underwent CAC scan and CCTA. CACS was categorized as 0, 1-10, 11-100, 101-400, and >400. Patients with CACS 0 were stratified according to the visual presence of coronary plaques on CCTA. Plaque composition was categorized as non-calcified (NCP), mixed (MP) and calcified (CP). The primary outcome was a major adverse cardiac event (MACE) which was defined as death and myocardial infarction.

RESULTS

Of 4049 patients, 1741 (43%) had a CACS 0. NCP and plaques that contained calcium (MP or CP) were detected by CCTA in 110 patients (6% of CACS 0) and 64 patients (4% of CACS 0), respectively. During a 5.6 years median follow-up (IQR 5.1-6.2 years), 413 MACE events occurred (13%). Patients with CACS 0 and MP/CP detected by CCTA had similar MACE risk compared to patients with CACS 1-10 (p = 0.868). In patients with CACS 0, after adjustment for risk factors and symptom, MP/CP was associated with an increased MACE risk compared to those with entirely normal CCTA (HR 2.39, 95% CI [1.09-5.24], p = 0.030).

CONCLUSIONS

A small but non-negligible proportion of patients with CACS 0 had identifiable coronary calcification, which was associated with increased MACE risk. Modifying CAC image acquisition and/or scoring methods could improve the detection of subtle coronary calcification.

Morphomic calcification score from clinical CT scans: A proxy for coronary artery calcium

BACKGROUND

Screening of cardiovascular risk is essential in preventing cardiac events and quantifying asymptomatic risk. Coronary artery calcium (CAC) scores are a well-established in predicting cardiovascular risk, but require specialized computed tomography (CT) scans. Given the relationship of aortic calcification with cardiovascular risk, we sought to determine whether aortic calcification measures from incidental CT scans may approximate CAC.

STUDY DESIGN

Retrospective CT scans and corresponding volumetric CAC scores were obtained from patients at the University of Michigan. Aortic calcifications were measured in 166 scans. Correlations between a novel morphomic calcium (MC) percent score and CAC score were evaluated using Kendall's correlation coefficients. Comparison of receiver operating characteristic (ROC) curves based on MC at different vertebral levels showed the highest predictive values for measures taken at L4.

RESULTS

MC at L4 shows promise in predicting CAC (AUC 0.90 in non-contrast scans, 0.70 in post-contrast scans). Proposed MC threshold are (4.21% for best sensitivity, B 12.93% for balance, C = 19.26% for specificity) in scans without contrast enhancement and (D = 7.31 for sensitivity, E 8.06 for specificity) in scans with contrast enhancement.

CONCLUSION

The MC score demonstrates promising potential in approximating CAC, particularly at the L4 level. The utilization of MC from incidental CT scans may be useful for assessment of cardiovascular risk. The ability to extract MC from contrast scans makes it especially valuable to patients receiving additional medical or surgical care. Recognition of high-risk patients would allow the use of indicated preventative strategies to avoid hard cardiovascular events in at risk patients.

The relationship between volumetric thoracic bone mineral density and coronary calcification in men and women - results from the Copenhagen General Population Study

BACKGROUND

The association between low bone mineral density (BMD) and the presence of coronary artery calcium (CAC) as a marker of atherosclerosis is unclear. The aim of this study was to assess the potential relationship between volumetric thoracic bone mineral density and coronary calcification in a large population of men and women.

METHODS

Participants from the Copenhagen General Population Study underwent multidetector computed tomography. Volumetric thoracic BMD and CAC were assessed in the same scan. CAC was measured using calibrated mass score (cMS). cMS was dichotomized as cMS = 0 or cMS > 0. The association between BMD and cMS was analyzed using multiple logistic regression in men, premenopausal and postmenopausal women. The model was adjusted for age, BMI, hypertension, hypercholesterolemia, diabetes, known cardiovascular disease and smoking.

RESULTS

Of 2548 eligible participants, 1163 men and 1385 women, mean age 61 ± 10 were included in the study. Mean BMD was 138 ± 46 mg/cm³ for men and 151 ± 49 mg/cm³ women. In 696 men (67%) and 537 women (41%) cMS was found to be above zero. For men, a decrease in BMD of 100 mg/cm³ was associated to an odds ratio of 1.49 for cMS > 0 (95% confidence interval: 1.04-2.13, P = 0.03). In postmenopausal women, a decrease in BMD of 100 mg/cm³ was associated to an odds ratio of 1.47 for MS > 0 (95% confidence interval: 1.04-2.08, P = 0.03). For premenopausal women, no significant association was found between BMD and cMS (odds ratio = 0.74, 95% confidence interval: 0.36-1.52, P = 0.4).

CONCLUSION

Bone mineral density and coronary calcification are inversely related in both men and postmenopausal women, supporting the hypothesis that a direct relation between bone loss and development of atherosclerosis exists irrespective of gender.

Coronary calcium scoring with partial volume correction in anthropomorphic thorax phantom and screening chest CT images

INTRODUCTION

The amount of coronary artery calcium determined in CT scans is a well established predictor of cardiovascular events. However, high interscan variability of coronary calcium quantification may lead to incorrect cardiovascular risk assignment. Partial volume effect contributes to high interscan variability. Hence, we propose a method for coronary calcium quantification employing partial volume correction.

METHODS

Two phantoms containing artificial coronary artery calcifications and 293 subject chest CT scans were used. The first and second phantom contained nine calcifications and the second phantom contained three artificial arteries with three calcifications of different volumes, shapes and densities. The first phantom was scanned five times with and without extension rings. The second phantom was scanned three times without and with simulated cardiac motion (10 and 30 mm/s). Chest CT scans were acquired without ECG-synchronization and reconstructed using sharp and soft kernels. Coronary calcifications were annotated employing the clinically used intensity value thresholding (130 HU). Thereafter, a threshold separating each calcification from its background was determined using an Expectation-Maximization algorithm. Finally, for each lesion the partial content of calcification in each voxel was determined depending on its intensity and the determined threshold.

RESULTS

Clinical calcium scoring resulted in overestimation of calcium volume for medium and high density calcifications in the first phantom, and overestimation of calcium volume for high density and underestimation for low density calcifications in the second phantom. With induced motion these effects were further emphasized. The proposed quantification resulted in better accuracy and substantially lower over- and underestimation of calcium volume even in presence of motion. In chest CT, the agreement between calcium scores from the two reconstructions improved when proposed method was used.

CONCLUSION

Compared with clinical calcium scoring, proposed quantification provides a better estimate of the true calcium volume in phantoms and better agreement in calcium scores between different subject scan reconstructions.

Coronary Artery Calcium Scoring: Is It Time for a Change in Methodology?

Quantification of coronary artery calcium (CAC) has been shown to be reliable, reproducible, and predictive of cardiovascular risk. Formal CAC scoring was introduced in 1990, with early scoring algorithms notable for their simplicity and elegance. Yet, with little evidence available on how to best build a score, and without a conceptual model guiding score development, these scores were, to a large degree, arbitrary. In this review, we describe the traditional approaches for clinical CAC scoring, noting their strengths, weaknesses, and limitations. We then discuss a conceptual model for developing an improved CAC score, reviewing the evidence supporting approaches most likely to lead to meaningful score improvement (for example, accounting for CAC density and regional distribution). After discussing the potential implementation of an improved score in clinical practice, we follow with a discussion of the future of CAC scoring, asking the central question: do we really need a new CAC score?

Influence of heart rate on coronary calcium scores: a multi-manufacturer phantom study

To evaluate the influence of heart rate on coronary calcium scores (CCS) using a dynamic phantom on four high-end computed tomography (CT) systems from different manufacturers. Artificial coronary arteries were moved in an anthropomorphic chest phantom at linear velocities, corresponding to < 60, 60-75 and > 75 beats per minute (bpm). Data was acquired with routinely used clinical protocols for CCS on four high-end CT systems (CT1-CT4). CCS, quantified as Agatston and mass scores were compared to reference scores at < 60 bpm. Influence of heart rate was assessed for each system with the cardiac motion susceptibility (CMS) Index. At increased heart rates (> 75 bpm), Agatston scores of the low mass calcification were similar to the reference score, while Agatston scores of the medium and high mass calcification increased significantly up to 50% for all CT systems. Threefold CMS increases at > 75 bpm in comparison with < 60 bpm were shown. For medium and high mass calcifications, significant differences in CMS between CT systems were found. Heart rate substantially influences CCS for high-end CT systems of four major manufacturers, but CT systems differ in motion susceptibility. Follow-up CCS CT scans should be acquired on the same CT system and protocol, and preferably with comparable heart rates.

Noninvasive Coronary Plaque Imaging

Early identification of high-risk or vulnerable atherosclerotic plaques prone to rupture and performing preemptive therapy prior to catastrophic cardiovascular events are optimal goals of plaque imaging. Despite the advances in imaging modalities to identify vulnerable characteristics, the predictive value of the imaging techniques in the clinical setting is still developing. In this regard, reliable and high-sensitive imaging modalities identifying vulnerable plaque characters that may lead to future cardiovascular events will be useful. In this review article, we describe a current non-invasive plaque imaging technique to identify high-risk coronary plaque features.

Guideline-Based Statin Eligibility, Cancer Events, and Noncardiovascular Mortality in the Framingham Heart Study

Purpose Cancer and cardiovascular disease share risk factors, and there is some evidence that statins reduce cancer mortality. We sought to determine the accuracy of the 2013 American College of Cardiology/American Heart Association statin eligibility criteria to identify individuals at a higher risk of developing cancer or of dying as a result of cancer or other noncardiovascular causes. Methods We included 2,196 participants (50.5 ± 8.1 years of age; 55% female) who were statin naïve and free of cancer at baseline from the offspring and third-generation cohorts of the community-based longitudinal Framingham Heart Study. Statin eligibility was determined per American College of Cardiology/American Heart Association guidelines, and subclinical coronary atherosclerosis was assessed by computed tomography. The primary outcome was incident cancer at a median of 10.0 years (interquartile range, 9.1-10.6 years) of follow-up, and secondary outcomes were cancer mortality and noncardiovascular mortality. Results The incident cancer rate was 11.2% (247 of 2,196), with 58 noncardiovascular deaths, including 39 cancer deaths (1.8%). Overall, 37% (812 of 2,196) were statin eligible. Incident cancer occurred in 125 (15%) of the 812 statin-eligible participants versus 122 (8.8%) of the 1,384 of noneligible participants (subdistribution hazard ratio [SDHR], 1.8 [1.4 to 2.3]; P < .001). Cancer mortality occurred in 34 (4.2%) of the 812 statin-eligible participants versus five (0.4%) of the 1,384 noneligible participants (SDHR, 12.1 [4.7 to 31]; P < .001). Noncardiovascular mortality occurred in 49 (6.0%) of the 812 statin-eligible participants versus nine (0.7%) of the 1,384 noneligible participants (SDHR, 10.1 [5.0 to 21]; P < .001). In stratified analyses, these findings were independent of any individual causative risk factor such as body mass index, age, or smoking status. Conclusion In this community-based primary prevention cohort, guideline-based statin eligibility accurately identified patients at a higher risk of developing cancer and cancer-related mortality. Shared risk profiles and potential benefits of statins between cancer and cardiovascular outcomes may provide a unique opportunity to improve population health.

Prospective evaluation of the influence of iterative reconstruction on the reproducibility of coronary calcium quantification in reduced radiation dose 320 detector row CT

BACKGROUND

Coronary artery calcium (CAC) predicts coronary heart disease events and is important for individualized cardiac risk assessment. This report assesses the interscan variability of CT for coronary calcium quantification using image acquisition with standard and reduced radiation dose protocols and whether the use of reduced radiation dose acquisition with iterative reconstruction (IR; "reduced-dose/IR ") allows for similar image quality and reproducibility when compared to standard radiation dose acquisition with filtered back projection (FBP; "standard-dose/FBP") on 320-detector row computed tomography (320-CT).

METHODS

200 consecutive patients (60 ± 9 years, 59% male) prospectively underwent two standard- and two reduced-dose acquisitions (800 total scans, 1600 reconstructions) using 320 slice CT and 120 kV tube voltage. Automated tube current modulation was used and for reduced-dose scans, prescribed tube current was lowered by 70%. Image noise and Agatston scores were determined and compared.

RESULTS

Regarding stratification by Agatston score categories (0, 1-10, 11-100, 101-400, >400), reduced-dose/IR versus standard-dose/FBP had excellent agreement at 89% (95% CI: 86-92%) with kappa 0.86 (95% CI: 0.81-0.90). Standard-dose/FBP rescan agreement was 93% (95% CI: 89-96%) with kappa = 0.91 (95% CI: 0.86-0.95) while reduced-dose/IR rescan agreement was similar at 91% (95% CI: 87-94%) with kappa 0.88 (95% CI: 0.83-0.93). Image noise was significantly higher but clinically acceptable for reduced-dose/IR (18 Hounsfield Unit [HU] mean) compared to standard-dose/FBP (16 HU; p < 0.0001). Median radiation exposure was 74% lower for reduced- (0.37 mSv) versus standard-dose (1.4 mSv) acquisitions.

CONCLUSION

Rescan agreement was excellent for reduced-dose image acquisition with iterative reconstruction and standard-dose acquisition with filtered back projection for the quantification of coronary calcium by CT. These methods make it possible to reduce radiation exposure by 74%.

CLINICAL TRIAL REGISTRATION

URL: https://clinicaltrials.gov/ct2/show/NCT01621594.

UNIQUE IDENTIFIER

NCT01621594.

Coronary atherosclerosis burden is not advanced in patients with β-thalassemia despite premature extracardiac atherosclerosis: a coronary artery calcium score and carotid intima-media thickness study

Background

Thalassemic patients demonstrate an increased rate of extracardiac vascular complications and increased carotid wall intima-media thickness (cIMT), but very low prevalence of coronary artery disease (CAD). We investigated the atheroma burden by assessing the coronary artery calcium (CAC) and cIMT in these patients.

Methods

We examined 37 patients with β-thalassemia and 150 healthy control volunteers with multi-detector computer tomography (CT) and ultrasonography to determine CAC score and cIMT, respectively.

Results

Propensity score matching (C-statistic: 0.88; 95% CI: 0.83–0.93) resulted in 27 pairs of patients; severe CAC was observed in 2 (7.4%) and 0 of β-thalassemia patients and healthy volunteers respectively (P = 0.5). Median calcium score was 0 (0–0) in β-thalassemia patients and 0 (0–4) in healthy volunteers (P = 0.8). Median intima-media thickness was higher in β-thalassemia patients compared to control group [0.45 (0.06–0.65) vs. 0.062 (0.054–0.086); P = 0.04].

Conclusions

Patients with β–thalassemia in comparison with healthy control subjects exhibit similar CAC score and increased cIMT. Our findings indicate a disparate rate of progression of atherosclerosis between coronary and extracardiac arteries in these patients lending support to the epidemiological evidence.

Cardiovascular Event Prediction and Risk Reclassification by Coronary, Aortic, and Valvular Calcification in the Framingham Heart Study

BACKGROUND

We determined whether vascular and valvular calcification predicted incident major coronary heart disease, cardiovascular disease (CVD), and all-cause mortality independent of Framingham risk factors in the community-based Framingham Heart Study.

METHODS AND RESULTS

Coronary artery calcium (CAC), thoracic and abdominal aortic calcium, and mitral or aortic valve calcium were measured by cardiac computed tomography in participants free of CVD. Participants were followed for a median of 8 years. Multivariate Cox proportional hazards models were used to determine association of CAC, thoracic and abdominal aortic calcium, and mitral and aortic valve calcium with end points. Improvement in discrimination beyond risk factors was tested via the C-statistic and net reclassification index. In this cohort of 3486 participants (mean age 50±10 years; 51% female), CAC was most strongly associated with major coronary heart disease, followed by major CVD, and all-cause mortality independent of Framingham risk factors. Among noncoronary calcifications, mitral valve calcium was associated with major CVD and all-cause mortality independent of Framingham risk factors and CAC. CAC significantly improved discriminatory value beyond risk factors for coronary heart disease (area under the curve 0.78-0.82; net reclassification index 32%, 95% CI 11-53) but not for CVD. CAC accurately reclassified 85% of the 261 patients who were at intermediate (5-10%) 10-year risk for coronary heart disease based on Framingham risk factors to either low risk (n=172; no events observed) or high risk (n=53; observed event rate 8%).

CONCLUSIONS

CAC improves discrimination and risk reclassification for major coronary heart disease and CVD beyond risk factors in asymptomatic community-dwelling persons and accurately reclassifies two-thirds of the intermediate-risk population.

Coronary artery calcium: 0.5 mm slice-thickness reconstruction with adjusted attenuation threshold outperforms 3.0 mm by validating against spatially registered intravascular ultrasound with radiofrequency backscatter

RATIONALE AND OBJECTIVES

Coronary artery calcium (CAC) images can be reconstructed with thinner slice thickness on some modern multidetector-row computed tomography scanners without additional radiation. We hypothesized that the isotropic 0.5-mm CAC reconstruction outperforms the conventional 3.0-mm reconstruction in detecting and quantifying coronary calcium, and we proposed to compare them by validating against spatially registered intravascular ultrasound with radiofrequency backscatter-virtual histology (IVUS-VH).

MATERIALS AND METHODS

Twenty-seven patients were enrolled, and 5976 mm of coronary arteries were analyzed. A semiautomatic software was developed to coregister CAC and IVUS-VH on a detailed slice-by-slice basis. Calcium detection and calcium volume quantification were evaluated and compared using varying calcium attenuation thresholds. Algorithms for deriving individualized optimal threshold and comparable Agatston score on the 0.5-mm reconstruction were developed.

RESULTS

The isotropic 0.5-mm reconstruction achieved significantly higher area under receiver-operating curve than the conventional 3.0-mm reconstruction (0.9 vs. 0.74, P < .001). Using the optimal threshold, the 0.5-mm reconstruction had higher sensitivity (0.79 vs. 0.65), specificity (0.85 vs. 0.77), positive predictive value (0.42 vs. 0.29), and negative predictive value (0.97 vs. 0.94) than the 3.0 mm. Individualized optimal threshold was significantly correlated with the image noise (r = 0.66, P < .001) in the 0.5-mm reconstruction.

CONCLUSIONS

By optimizing the calcium threshold, the 0.5-mm reconstruction is superior to the conventional 3.0-mm in detecting and quantifying calcium, which may improve the clinical value of CAC without additional radiation.

Comparison of adaptive statistical iterative and filtered back projection reconstruction techniques in quantifying coronary calcium

BACKGROUND

Adaptive statistical iterative reconstruction (ASIR) has been used to reduce radiation dose in cardiac computed tomography. However, change of image parameters by ASIR as compared to filtered back projection (FBP) may influence quantification of coronary calcium.

OBJECTIVE

To investigate the influence of ASIR on calcium quantification in comparison to FBP.

METHODS

In 352 patients, CT images were reconstructed using FBP alone, FBP combined with ASIR 30%, 50%, 70%, and ASIR 100% based on the same raw data. Image noise, plaque density, Agatston scores and calcium volumes were compared among the techniques.

RESULTS

Image noise, Agatston score, and calcium volume decreased significantly with ASIR compared to FBP (each P < 0.001). Use of ASIR reduced Agatston score by 10.5% to 31.0%. In calcified plaques both of patients and a phantom, ASIR decreased maximum CT values and calcified plaque size.

CONCLUSION

In comparison to FBP, adaptive statistical iterative reconstruction (ASIR) may significantly decrease Agatston scores and calcium volumes.

Guideline-Based Statin Eligibility, Coronary Artery Calcification, and Cardiovascular Events

IMPORTANCE

The 2013 American College of Cardiology/American Heart Association (ACC/AHA) guidelines for cholesterol management defined new eligibility criteria for statin therapy. However, it is unclear whether this approach improves identification of adults at higher risk of cardiovascular events.

OBJECTIVE

To determine whether the ACC/AHA guidelines improve identification of individuals who develop incident cardiovascular disease (CVD) and/or have coronary artery calcification (CAC) compared with the National Cholesterol Education Program's 2004 Updated Third Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (ATP III) guidelines.

DESIGN, SETTING, AND PARTICIPANTS

Longitudinal community-based cohort study, with participants for this investigation drawn from the offspring and third-generation cohorts of the Framingham Heart Study. Participants underwent multidetector computed tomography for CAC between 2002 and 2005 and were followed up for a median of 9.4 years for incident CVD.

EXPOSURES

Statin eligibility was determined based on Framingham risk factors and low-density lipoprotein thresholds for ATP III, whereas the pooled cohort calculator was used for ACC/AHA.

MAIN OUTCOMES AND MEASURES

The primary outcome was incident CVD (myocardial infarction, death due to coronary heart disease [CHD], or ischemic stroke). Secondary outcomes were CHD and CAC (as measured by the Agatston score).

RESULTS

Among 2435 statin-naive participants (mean age, 51.3 [SD, 8.6] years; 56% female), 39% (941/2435) were statin eligible by ACC/AHA compared with 14% (348/2435) by ATP III (P < .001). There were 74 incident CVD events (40 nonfatal myocardial infarctions, 31 nonfatal ischemic strokes, and 3 fatal CHD events). Participants who were statin eligible by ACC/AHA had increased hazard ratios for incident CVD compared with those eligible by ATP III: 6.8 (95% CI, 3.8-11.9) vs 3.1 (95% CI, 1.9-5.0), respectively (P<.001). Similar results were seen for CVD in participants with intermediate Framingham Risk Scores and for CHD. Participants who were newly statin eligible (n = 593 [24%]) had an incident CVD rate of 5.7%, yielding a number needed to treat of 39 to 58. Participants with CAC were more likely to be statin eligible by ACC/AHA than by ATP III: CAC score >0 (n = 1015): 63% vs 23%; CAC score >100 (n = 376): 80% vs 32%; and CAC score >300 (n = 186): 85% vs 34% (all P < .001). A CAC score of 0 identified a low-risk group among ACC/AHA statin-eligible participants (306/941 [33%]) with a CVD rate of 1.6%.

CONCLUSIONS AND RELEVANCE

In this community-based primary prevention cohort, the ACC/AHA guidelines for determining statin eligibility, compared with the ATP III, were associated with greater accuracy and efficiency in identifying increased risk of incident CVD and subclinical coronary artery disease, particularly in intermediate-risk participants.

CT attenuation values of blood and myocardium: rationale for accurate coronary artery calcifications detection with multi-detector CT

Objectives

To determine inter-session and intra/inter-individual variations of the attenuations of aortic blood/myocardium with MDCT in the context of calcium scoring. To evaluate whether these variations are dependent on patients’ characteristics.

Methods

Fifty-four volunteers were evaluated with calcium scoring non-enhanced CT. We measured attenuations (inter-individual variation) and standard deviations (SD, intra-individual variation) of the blood in the ascending aorta and of the myocardium of left ventricle. Every volunteer was examined twice to study the inter-session variation. The fat pad thickness at the sternum and noise (SD of air) were measured too. These values were correlated with the measured aortic/ventricular attenuations and their SDs (Pearson). Historically fixed thresholds (90 and 130 HU) were tested against different models based on attenuations of blood/ventricle.

Results

The mean attenuation was 46HU (range, 17-84HU) with mean SD 23HU for the blood, and 39HU (10-82HU) with mean SD 18 HU for the myocardium. The attenuation/SD of the blood were significantly higher than those of the myocardium (p<0.01). The inter-session variation was not significant. There was a poor correlation between SD of aortic blood/ventricle with fat thickness/noise. Based on existing models, 90 HU threshold offers a confidence interval of approximately 95% and 130 HU more than 99%.

Conclusions

Historical thresholds offer high confidence intervals for exclusion of aortic blood/myocardium and by the way for detecting calcifications. Nevertheless, considering the large variations of blood/myocardium CT values and the influence of patient’s characteristics, a better approach might be an adaptive threshold.

Correlations between aortic root calcification and coronary artery atherosclerotic markers assessed using multidetector computed tomography

RATIONALE AND OBJECTIVES

Atherosclerosis is a systemic process associated with arterial calcification in multiple vascular beds. This study investigated correlations between aortic root calcification (ARC) quantified using Agatston and volumetric scoring methods with coronary atherosclerotic markers (coronary artery calcification [CAC], calcified plaques, and luminal stenosis).

MATERIALS AND METHODS

This cross-sectional study was carried out between January and December 2013. One hundred ninety-six consecutive patients with intermediate pretest probability of ischemic heart disease who underwent 64-slice multidetector computed tomography angiography were recruited, with 175 patients being eligible to enroll in the study.

RESULTS

A significant correlation was observed between ARC and total CAC using the Agatston and volumetric scoring methods (r = 0.225; P = .003 and r = 0.243; P = .001, respectively). With regard to individual coronary vessel calcification and ARC, a significant correlation was observed between ARC and left main stem artery calcification calculated using the volumetric and Agatston scoring methods (P < .05). A significant correlation was observed between high ARC and presence of coronary calcified plaque measured using the Agatston and volumetric scoring methods. A strong correlation was also observed between ARC and number of coronary stenotic vessels measured using the Agatston and volumetric scoring methods (r = 0.67; P < .001 and r = 0.63; P < .001, respectively).

CONCLUSIONS

ARC can be used as an additional marker to assess coronary atherosclerosis and may have a complementary role with CAC for detection of coronary artery disease.

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.

Noncalcified coronary plaque volumes in healthy people with a family history of early onset coronary artery disease

BACKGROUND

Although age and sex distributions of calcified coronary plaque have been well described in the general population, noncalcified plaque (NCP) distributions remain unknown. This is important because NCP is a putative precursor for clinical coronary artery disease and could serve as a sentinel for aggressive primary prevention, especially in high-risk populations. We examined the distributions of NCP and calcified coronary plaque in healthy 30- to 74-year-old individuals from families with early onset coronary artery disease.

METHODS AND RESULTS

Participants in the GeneSTAR family study (N=805), mean age 51.1±10.8 years, 56% women, were screened for coronary artery disease risk factors and coronary plaque using dual-source computed tomographic angiography. Plaque volumes (mm(3)) were quantified using a validated automated method. The prevalence of coronary plaque was 57.8% in men and 35.8% in women (P<0.0001). NCP volume increased with age (P<0.001) and was higher in men than women (P<0.001). Although NCP, as a percentage of total plaque, was inversely related to age (P<0.01), NCP accounted for most of the total plaque volume at all ages, especially in men and women <55 years (>70% and >80%, respectively). Higher Framingham risk was associated with the number of affected vessels (P<0.01), but 44% of men and 20.8% of women considered intermediate risk had left main and 3-vessel disease involvement.

CONCLUSIONS

The majority of coronary plaque was noncalcified, particularly in younger individuals. These findings support the importance of assessing family history and suggest that early primary prevention interventions may be warranted at younger ages in families with early onset coronary artery disease.

The relationship between serum hypoxia-inducible factor 1α and coronary artery calcification in asymptomatic type 2 diabetic patients

Background

Hypoxia-inducible factor 1 (HIF-1), a master regulator of oxygen homeostasis, is a heterodimer consisting of HIF-1α and HIF-1β subunits, and is implicated in calcification of cartilage and vasculature. The goal of this study was to determine the relationship between serum HIF-1α with coronary artery calcification (CAC) in patients with type 2 diabetes.

Methods

The subjects were 405 (262 males, 143 females, age 51.3 ± 6.4 years) asymptomatic patients with type 2 diabetes mellitus. Serum HIF-1α and interleukin-6 (IL-6) levels were measured by ELISA. CAC scores were assessed by a 320-slice CT scanner. The subjects were divided into 4 quartiles depending on serum HIF-1α levels.

Results

Average serum HIF-1α was 184.4 ± 66.7 pg/ml. Among patients with higher CAC scores, HIF-1α levels were also significantly increased (p <0.001). HIF-1α levels positively correlated with CRP, IL-6, UKPDS risk score, HbA1c, FBG, and CACS, but did not correlate with diabetes duration, age, and LDL. According to the multivariate analysis, HIF-1α levels significantly and independently predict the presence of CAC. ROC curve analysis showed that the serum HIF-1α level can predict the extent of CAC, but the specificity was lower than the traditional risk factors UKPDS and HbA1c.

Conclusion

As a marker of hypoxia, serum HIF-1α level may be an independent risk factor for the presence of CAC. These findings indicate that elevated serum HIF-1α may be involved in vascular calcification in patients with type 2 diabetes mellitus.

Distribution of abdominal aortic calcium by computed tomography: impact of analysis method on quantitative calcium score

RATIONALE AND OBJECTIVES

Abdominal aortic calcification (AAC) can be quantified using computed tomography (CT), but imaging planes are prescribed based on bony landmarks, so that individual variation between the landmark and the aortoiliac junction can result in variable aortic coverage. In the Framingham CT substudy, we scanned a 15-cm (Z-direction) abdominal segment cranial to the S1 vertebral body. We sought to determine the range and distribution of length of aorta scanned and the distribution of AAC within the abdominal aorta and to compare burden of AAC measured from fixed-length segments versus AAC from all slices cranial to the aortoiliac bifurcation.

MATERIALS AND METHODS

AAC was quantified by modified Agatston score (AS) in 100 Framingham Heart Study participants (60 ± 13 years old, 51 men). We compared the AS measured from 5-cm and 8-cm segments with the ASALL (total visualized aorta).

RESULTS

Of 100, 73 participants had AAC >0. The total length of aorta imaged was ≥8 cm in 84% of participants. Qualitatively, 5-cm and 8-cm segments correctly identified 96% and 99%, respectively, of participants as having or not having AAC. Quantitatively, AS8cm was within 20% of ASALL in four-fifths and within 30% of ASALL in nine-tenths of participants. AS5cm more severely underestimated ASALL.

CONCLUSION

The use of S1 as the caudal imaging landmark in a 15-cm slab yields ≥8 cm aortic coverage in most adults. Both 5-cm and 8-cm analysis strategies are comparable to analyzing the total visualized abdominal aorta for prevalent AAC, but only 8-cm segment analysis yields quantitatively similar measures of AAC.