The Coronary Atlas

The coronary atlas project aims to understand individual differences in the blood flow environment to generate insights into disease susceptibility for prevention and treatment improvement.

For heart disease patients worldwide

Describing the detailed statistical anatomy of the coronary artery tree is important for determining the ætiology of heart disease. A number of studies have investigated geometrical features and have found that these correlate with clinical outcomes, e.g. bifurcation angle with major adverse cardiac events.

These methodologies were mainly two-dimensional, manual and prone to inter-observer variability, and the data commonly relates to cases already with pathology.

In contrast, the Coronary Atlas uses hybrid atlasing methodology to build a population of computational models of the coronary arteries to comprehensively and accurately assess anatomy including 3D size, geometry and shape descriptors.

A random sample of more than 1200 cardiac 64-CT 3D scans with a calcium score of zero was segmented and analysed using a standardised protocol. The resulting atlas includes, but is not limited to, the distributions of the coronary tree in terms of angles, diameters, centrelines, principal component shape analysis and cross-sectional contours.

This novel resource will facilitate the improvement of stent design and provide a reference for hemodynamic simulations, and provides a basis for large normal and pathological databases.

Global context 

Global mortality rate

  • Coronary artery disease
  • Stroke
  • Dementia
  • Diabetes
  • Cancer

A coronary event happens every…

The cost of coronary disease USD

Publications

 

 

Combining medical and engineering sciences

Construction of a coronary atlas from CT angiography
Medrano-Gracia, P., et al. Construction of a coronary atlas from CT angiography. in Medical Image Computing and Computer Assisted Intervention. 2014. Boston, USA.

Describing the detailed statistical anatomy of the coronary artery tree is important for determining the ætiology of heart disease. A number of studies have investigated geometrical features and have found that these correlate with clinical outcomes, e.g. bifurcation angle with major adverse cardiac events.

These methodologies were mainly two-dimensional, manual and prone to inter-observer variability, and the data commonly relates to cases already with pathology. We propose a hybrid atlasing methodology to build a population of computational models of the coronary arteries to comprehensively and accurately assess anatomy including 3D size, geometry and shape descriptors.

A random sample of 122 cardiac CT scans with a calcium score of zero was segmented and analysed using a standardised protocol. The resulting atlas includes, but is not limited to, the distributions of the coronary tree in terms of angles, diameters, centrelines, principal component shape analysis and cross-sectional contours. This novel resource will facilitate the improvement of stent design and provide a reference for hemodynamic simulations, and provides a basis for large normal and pathological databases.

A Study of Coronary Bifurcation Shape in a Normal Population

Medrano-Gracia, P., et al., A Study of Coronary Bifurcation Shape in a Normal Population. Journal of Cardiovascular Translational Research, 2016: p. 1-9.

Abstract

During percutaneous coronary intervention, stents are placed in narrowings of the arteries to restore normal blood flow. Despite improvements in stent design, deployment techniques and drug-eluting coatings, restenosis and stent thrombosis remain a significant problem.

Population stent design based on statistical shape analysis may improve clinical outcomes. Computed tomographic (CT) coronary angiography scans from 211 patients with a zero calcium score, no stenoses and no intermediate artery, were used to create statistical shape models of 446 major coronary artery bifurcations (left main, first diagonal and obtuse marginal and right coronary crux). Coherent point drift was used for registration.

Principal component analysis shape scores were tested against clinical risk factors, quantifying the importance of recognised shape features in intervention including size, angles and curvature. Significant differences were found in (1) vessel size and bifurcation angle between the left main and other bifurcations; (2) inlet and curvature angle between the right coronary crux and other bifurcations; and (3) size and bifurcation angle by sex.

Hypertension, smoking history and diabetes did not appear to have an association with shape. Physiological diameter laws were compared, with the Huo-Kassab model having the best fit. Bifurcation coronary anatomy can be partitioned into clinically meaningful modes of variation showing significant shape differences.

A computational atlas of normal coronary bifurcation shape, where disease is common, may aid in the design of new stents and deployment techniques, by providing data for bench-top testing and computational modelling of blood flow and vessel wall mechanics.

A Computational Atlas of Normal Coronary Artery Anatomy

Medrano-Gracia, P., et al., A Computational Atlas of Normal Coronary Artery Anatomy. EuroIntervention, 2016. EIJ-D- 16-00111(in press).

Aims

The aim of this study was to define the shape variations, including diameters and angles, of the major coronary artery bifurcations.

Method and results

Computed tomographic angiograms from 300 adults with a zero calcium score and no stenoses were segmented for centreline and luminal models. A computational atlas was constructed enabling automatic quantification of 3D angles, diameters and lengths of the coronary tree. The diameter (mean±SD) of the left main coronary was 3.5±0.8 mm and the length 10.5±5.3 mm. The left main bifurcation angle (distal angle or angle B) was 89±21° for cases with, and 75±23° for those without an intermediate artery (p<0.001). Analogous measurements of diameter and angle were tabulated for the other major bifurcations (left anterior descending/diagonal, circumflex/obtuse marginal and right coronary crux). Novel 3D angle definitions are proposed and analysed.

Conclusions

A computational atlas of normal coronary artery anatomy provides distributions of diameter, lengths and bifurcation angles as well as more complex shape analysis. These data define normal anatomical variation, facilitating stent design, selection and optimal treatment strategy. These population models are necessary for accurate computational flow dynamics, can be 3D printed for bench testing bifurcation stents and deployment strategies, and can aid in the discussion of different approaches to the treatment of coronary bifurcations.

Impact of bifurcation angle and other anatomical characteristics on blood flow–A computational study of non-stented and stented coronary arteries.

Beier, S., et al., Impact of bifurcation angle and other anatomical characteristics on blood flow–A computational study of non-stented and stented coronary arteries. Journal of biomechanics, 2016. 49(9): p. 1570-1582.

Abstract

The hemodynamic influence of vessel shape such as bifurcation angle is not fully understood with clinical and quantitative observations being equivocal. The aim of this study is to use computational modeling to study the hemodynamic effect of shape characteristics, in particular bifurcation angle (BA), for non-stented and stented coronary arteries. Nine bifurcations with angles of 40°, 60° and 80°, representative of ±1 SD of 101 asymptomatic computed tomography angiogram cases (average age 54±8 years; 57 females), were generated for (1) a non-stented idealized, (2) stented idealized, and (3) non-stented patient-specific geometry.

Only the bifurcation angle was changed while the geometries were constant to eliminate flow effects induced by other vessel shape characteristics. The commercially available Biomatrix stent was used as a template and virtually inserted into each branch, simulating the T-stenting technique. Three patient-specific geometries with additional shape variation and ±2 SD BA variation (33°, 42° and 117°) were also computed.

Computational fluid dynamics (CFD) analysis was performed for all 12 geometries to simulate physiological conditions, enabling the quantification of the hemodynamic stress distributions, including a threshold analysis of adversely low and high wall shear stress (WSS), low time-averaged WSS (TAWSS), high spatial WSS gradient (WSSG) and high Oscillatory Shear Index (OSI) area.

The bifurcation angle had a minor impact on the areas of adverse hemodynamics in the idealized non-stented geometries, which fully disappeared once stented and was not apparent for patient geometries. High WSS regions were located close to the carina around peak-flow, and WSSG increased significantly after stenting for the idealized bifurcations.

Additional shape variations affected the hemodynamic profiles, suggesting that BA alone has little effect on a patient׳s hemodynamic profile. Incoming flow angle, diameter and tortuosity appear to have stronger effects. This suggests that other bifurcation shape characteristics and stent placement/strategy may be more important than bifurcation angle in atherosclerotic disease development, progression, and stent outcome.

Research

Coronary Flow Atlas

More than 2 million stents are implanted every year worldwide, but up to 8% of them still fail. That means that more than 160,000 affected patients experience severe complications, need to have repeated surgery and are at risk of sudden death world-wide every year.

Our team made it their goal to understand the reasons why stents still fail in some patients and not others.

We are currently expanding the largest database of coronary vessel shape, their blood flow and disease indicators to date. Sophisticated statistics can help us to understand which groups of patients are at higher risk of having disease and stent treatment failure. Magnetic resonance imaging and super-computer blood flow simulations are just some of the powerful tools we use to drive this research.

Ultimately, this can help heart disease patients worldwide by providing a reliable and early risk assessment, improving patient care and enabling patient-specific treatment.

Stenting considerations

Stents are tiny meshed wired tubes which function as scaffolds to re-open blocked blood vessels narrowed by disease. Stenting is usually very effective and is often the most preferred treatment method for later stage coronary artery disease.

But why do stents still fail in some patients and not others? What is the best stent design? Can stenting be personalised?

Our research wants to answer these questions to optimise stenting. This will move the current clinical practise of ‘one size fits all’ into a personalised treatment and will help more patients effectively by improving stenting success.

Variation in the population

The largest vessel bifurcation is the left main. It is commonly affected by disease and thus focus of many discussions amongst experts regarding the best treatment approach. Understanding difference in left mains in a large population can significantly help to improve treatment and translate it from a generic to a patient cantered approach, whereby individual differences are accounted for.

Disease maps for population groups

The coronary arteries consist of a left and a right main branch. Each continue to branch of into smaller and a smaller vessels. Bifurcations are the regions called where the vessels split.

The analysis of more than 200 patient’s medical images found that there are profound differences in the different bifurcations in one patient, but also vary significantly across patients with some common trends.  This has a significant impact in treating these vessel segments when diseased, whereby one stent may not fit all bifurcations or patients.

Machine learning to identify adverse vessel shape

Advances in computing hardware and machine learning are revolutionising data intensive research. By accumulating a large database of coronary arteries, we have a unique opportunity to use machine learning to improve risk modelling and the prediction of heart disease. In particular, we are interested in how the latest approaches in artificial neural networks could be used to develop software capable of helping medical specialists with early detection of at-risk patients. Our ambition is to use medical image data together with fluid-flow simulations to train deep neural networks capable of identifying adverse geometries and advance segmentation techniques.

Kernel Machine by SemperVinco is licensed under CC BY 4.0

Your role

The Coronary Atlas project welcomes collaboration and involvement by interested parties. If you are a researcher, cardiologist, developer or student with a professional interest in the project, please get in touch. 

Patients circular image

Patients

Want to know more about our research? Look at the Global context page, or listen to the RadioNZ interview of the atlas or flow experiments.

Cardiologists circular image

Cardiologists

Want to contribute? Contact the team. Keep updated with the latest interventional strategy recommendations see our talks.

researchers - get involved

Researchers

Do you want to contribute or us to share CTCA images, STL files for computing or 3D printing? Or access to the statistical data? No problem. Contact us for details.

developers circular image

Developers

Want to explore, have ideas or want to create your own? We are happy to chat. Contact us for details.

Students

We are currently recruiting Masters and Ph.D. students and are happy to accept interns. Contact us for more information.

Funding 

So far the Coronary Atlas has attracted over $886,000 in funding

Global mortality rate

Sponsors

University of Auckand logo
Auckland Heart Group logo
Cardiac Society of Australia and New Zealand logo
AMRF logo
Auckland District Health Board logo
National Heart Foundation logo

Collaborators

University of Auckand logo
University of Auckand logo
Mercy Angiography logo
Auckland Heart Group logo
Auckland MRI group logo
Waitemata dhb
Auckland District Health Board logo
New Zealand eScience Infrastructure logo

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