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Aims To evaluate the distribution of atherosclerosis at bifurcations with computed tomography coronary angiography (CTCA) and propose a novel CT-Medina classification for bifurcation lesions. Methods In 26 patients (age 55 ± 10 years, 81% male) imaged with CTCA, 39 bifurcations were studied. The bifurcations analysis included the proximal main vessel, the distal main vessel and the side branch (SB). Plaque contours were manually traced on CTCA; the lumen, vessel and plaque area were measured, as well as plaque burden (%). The carina cross-sections were divided into four equal parts according to the expected wall shear stress (WSS) to assess circumferential plaque distribution. All the bifurcation lesions were classified using the Medina classification and a novel CT-Medina classification combining lumen narrowing and plaque burden ≥70%. Results Presence of severe plaque (plaque burden ≥70%) by CTCA was demonstrated in 12.8% (5/39) of the proximal segments, 15.4% (6/39) of the distal segments and 7.7% (3/39) of the SB segments. The thickest plaque was located more often in low WSS parts of the carina cross-sections, whereas the flow divider was rarely affected. Although in the majority of bifurcations plaque was present, based on the Medina classification 92% of the assessed bifurcations were identified as 0,0,0. Characterization of bifurcation lesions using the new CT-Medina classification provided additional information in seven cases (18%) compared to the Medina classification Conclusion Atherosclerotic plaque is widely present in all bifurcation segments, even in the absence of coronary lumen stenosis. A CT-Medina classification combining lumen and plaque parameters is more informative than angiographic classification of bifurcation lesions and could potentially facilitate the decision-making on the treatment of these lesions. © 2014 Wiley Periodicals, Inc.

Objective: We evaluated the ability of 64-slice multidetector computed tomography (MDCT)-derived plaque parameters to detect and quantify coronary atherosclerosis, using intravascular ultrasound (IVUS) as the reference standard. Methods: In 32 patients, IVUS and 64-MDCT was performed. The MDCT and IVUS datasets of 44 coronary arteries were co-registered using a newly developed fusion technique and quantitative parameters were derived from both imaging modalities. The threshold of >0.5mm of maximum wall thickness was used to establish plaque presence on MDCT and IVUS. Results: We analyzed 1364 coregistered 1-mm coronary cross-sections and 255 segments of 5-mm length. Compared with IVUS, 64-MDCT enabled correct detection in 957 of 1109 cross-sections containing plaque (sensitivity 86%). In 180 of 255 cross-sections atherosclerosis was correctly excluded (specificity 71%). On the segmental level, MDCT detected 213 of 220 segments with any atherosclerotic plaque (sensitivity 96%), whereas the presence of any plaque was correctly ruled out in 28 of 32 segments (specificity 88%). Interobserver agreement for the detection of atherosclerotic cross-sections was moderate (Cohen's kappa coefficient K = 0.51), but excellent for the atherosclerotic segments (K = 1.0). Pearson's correlation coefficient for vessel plaque volumes measured by MDCT and IVUS was r = 0.91 (p < 0.001). Bland-Altman analysis showed a slight non-significant underestimation of any plaque volume by MDCT (p = 0.5), with a trend to underestimate noncalcified and overestimate mixed/calcified plaque volumes (p = 0.22 and p = 0.87 respectively). Conclusion: MDCT is able to detect and quantify atherosclerotic plaque. Further improvement in CT resolution is necessary for more reliable assessment of very small and distal coronary plaques. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Purpose: To determine the reproducibility, accuracy, and predictors of accuracy of computed tomography (CT) angiography to detect and characterize coronary atherosclerotic plaque as compared with intravascular ultrasound. Methods: Ten ex vivo human coronary arteries were imaged in a moving phantom by dual-source CT (collimation: 0.6 mm, reconstructed slice thickness: 0.4 mm) and intravascular ultrasound (IVUS). Coregistered crosssections were assessed at 0.4 mm intervals for the presence and composition of atherosclerotic plaque (noncalcified, mixed, and calcified) on CT and IVUS by independent readers to determine reader agreement and diagnostic accuracy. Quantitative measurements of lumen and plaque area, plaque eccentricity, and intimal thickness on IVUS were used to determine predictors for the detection of noncalcified plaque by CT. Results: Within 1002 coregistered cross-sections, the interobserver agreement to detect plaque on CT was K = 0.48, K = 0.42, and K = 1.00 for noncalcified, mixed, and calcified plaque; respectively. The sensitivity and specificity of CT was 57% out of 84% for noncalcified, 32% of 92% for mixed, and 56% of 93% for calcified plaque when compared with IVUS; respectively. Misclassification occurred in 68% of mixed and 43% of noncalcified plaques. The odds of detecting noncalcified plaque in CT independently increased by 56% (95% CI: 47%-77%, P < 0.0001) with every 0.1 mm increase in maximum intimal thickness as measured by IVUS. Detection rate for noncalcified plaques was poor for plaques 1 mm maximal intimal thickness (90%). Conclusion: Reader agreement and diagnostic accuracy for the detection of coronary atherosclerotic plaque vary with plaque composition. Intimal thickness independently predicts detection of noncalcified plaque by CT with excellent sensitivity for >1 mm thick plaques.

Aims: Early atherosclerosis is located in low wall shear-stress (WSS) regions, however plaques are also found in the high WSS sensing flow divider walls of coronary bifurcations. We assessed the plaque distribution and morphology near bifurcations non-invasively with 64-slice computed tomography in relation to the WSS distribution. Methods and results: We inspected 65 cross-sections near coronary bifurcations for the presence of plaque. Cross-sections were divided into four equal parts, which we numbered according to expected levels of WSS, with part I the lowest WSS (outer wall) and increasing WSS's in part II (inner bend), III (outer bend) and IV (flow divider). Of the cross-sections 88% had plaque. Of all parts I, 72% contained plaque. This was 62%, 38% and 31% in parts II, III and IV. In cross-sections with only 1 or 2 parts inflicted, plaque was found in part I and/or II in 94%. In 93% of the cross-sections with the flow divider inflicted, parts I and/or II were also inflicted. Plaque was never found exclusively in the flow divider part IV. Conclusions: We demonstrated that plaque is mostly present in low WSS regions, whereas plaque in high WSS regions is accompanied by plaque in adjacent low WSS regions. It is therefore plausible that plaque grows from the outer wall (low WSS) of the bifurcation towards the flow divider (high WSS).

To evaluate the distribution of atherosclerosis at bifurcations with computed tomography coronary angiography (CTCA) and propose a novel CT-Medina classification for bifurcation lesions.In 26 patients (age 55 ± 10 years, 81% male) imaged with CTCA, 39 bifurcations were studied. The bifurcations analysis included the proximal main vessel, the distal main vessel and the side branch (SB). Plaque contours were manually traced on CTCA; the lumen, vessel and plaque area were measured, as well as plaque burden (%). The carina cross-sections were divided into four equal parts according to the expected wall shear stress (WSS) to assess circumferential plaque distribution. All the bifurcation lesions were classified using the Medina classification and a novel CT-Medina classification combining lumen narrowing and plaque burden ≥70%.Presence of severe plaque (plaque burden ≥70%) by CTCA was demonstrated in 12.8% (5/39) of the proximal segments, 15.4% (6/39) of the distal segments and 7.7% (3/39) of the SB segments. The thickest plaque was located more often in low WSS parts of the carina cross-sections, whereas the flow divider was rarely affected. Although in the majority of bifurcations plaque was present, based on the Medina classification 92% of the assessed bifurcations were identified as 0,0,0. Characterization of bifurcation lesions using the new CT-Medina classification provided additional information in seven cases (18%) compared to the Medina classificationAtherosclerotic plaque is widely present in all bifurcation segments, even in the absence of coronary lumen stenosis. A CT-Medina classification combining lumen and plaque parameters is more informative than angiographic classification of bifurcation lesions and could potentially facilitate the decision-making on the treatment of these lesions.

Patient specific geometrical data on human coronary arteries can be reliably obtained multislice computer tomography (MSCT) imaging. MSCT cannot provide hemodynamic variables, and the outflow through the side branches must be estimated. The impact of two different models to determine flow through the side branches on the wall shear stress (WSS) distribution in patient specific geometries is evaluated. Murray's law predicts that the flow ratio through the side branches scales with the ratio of the diameter of the side branches to the third power. The empirical model is based on flow measurements performed by Doriot et al. (2000) in angiographically normal coronary arteries. The fit based on these measurements showed that the flow ratio through the side branches can best be described with a power of 2.27. The experimental data imply that Murray's law underestimates the flow through the side branches. We applied the two models to study the WSS distribution in 6 coronary artery trees. Under steady flow conditions, the average WSS between the side branches differed significantly for the two models: the average WSS was 8% higher for Murray's law and the relative difference ranged from -5% to +27%. These differences scale with the difference in flow rate. Near the bifurcations, the differences in WSS were more pronounced: the size of the low WSS regions was significantly larger when applying the empirical model (13%), ranging from -12% to +68%. Predicting outflow based on Murray's law underestimates the flow through the side branches. Especially near side branches, the regions where atherosclerotic plaques preferentially develop, the differences are significant and application of Murray's law underestimates the size of the low WSS region. (C) 2011 Elsevier Ltd. All rights reserved.

This paper presents a novel method for segmenting the coronary lumen in CTA data. The method is based on graph cuts, with edge-weights depending on the intensity of the centerline, and robust kernel regression. A quantitative evaluation in 28 coronary arteries from 12 patients is performed by comparing the semi-automatic segmentations to manual annotations. This evaluation showed that the method was able to segment the coronary arteries with high accuracy, compared to manually annotated segmentations, which is reflected in a Dice coefficient of 0.85 and average symmetric surface distance of 0.22 mm.

Generation of a reference standard from multiple manually annotated datasets is a non-trivial problem. This paper discusses the weighted averaging of 3D open curves, which we used to generate a reference standard for vessel tracking data. We show how weighted averaging can be implemented by applying the Mean Shift algorithm to paths, and discuss the details of our implementation. Our approach can handle cases where the observer centerlines take different branches in a natural way. The method has been evaluated on synthetic data, and has been used to generate reference centerlines for evaluation of vessel tracking algorithms.

Glagov et al. observed that positive, compensatory vascular remodeling during plaque build up prevents lumen narrowing until plaque burden, this is the relative plaque area to media bounded area, exceeds a threshold of 40% [1]. Until now it is not clear what mechanism controls the compensatory vascular remodeling during the atherosclerotic plaque build up and what determines absence or limits compensatory vascular remodeling. Plaque burden does not seem to reflect a parameter, which could serve as a limiting step in the known control process in the vascular system. For instance, healthy arteries control vascular remodeling by fluid flow induced shear stress via a number of endothelium dependent pathways [2]. The endothelium at the atherosclerotic plaque side is considered to be dysfunctional [2] and might thereby limit the remodeling process. Since plaques are mostly eccentric, we hypothesize that the healthy part of the artery (or plaque free wall) will respond to changes in shear stress and will determine the capacity of the arteries to remodel up till the moment of complete circumferential involvement of the disease. We investigated whether the size of the plaque free wall contributes to vascular remodeling over a 3 year period using serial intravascular ultrasound measurements by determining 1) the frequency of positive remodeling in segments with varying size of plaque free vessel wall 2) the degree of vascular remodeling for segments with varying size of plaque free vessel wall.Copyright © 2008 by ASME

Generation of a reference standard from multiple manually annotated datasets is a non-trivial problem. This paper discusses the weighted averaging of 3D open curves, which we used to generate a reference standard for vessel tracking data. We show how weighted averaging can be implemented by applying the Mean Shift algorithm to paths, and discuss the details of our implementation. Our approach can handle cases where the observer centerlines take different branches in a natural way. The method has been evaluated on synthetic data, and has been used to generate reference centerlines for evaluation of vessel tracking algorithms.

Aims: Early atherosclerosis is located in low wall shear-stress (WSS) regions, however plaques are also found in the high WSS sensing flowdivider walls of coronary bifurcations. We assessed the plaque distribution and morphology near bifurcations non-invasively with 64 slice computed tomography (MSCT) in relation to the WSS distribution. Methods and results: We inspected 65 cross-sections near coronary bifurcations for the presence of plaque. Cross-sections were divided into four equal parts, which we numbered according to expected levels of WSS, with part I the lowest WSS (outer wall) and increasing WSS’s in part II (inner bend), III (outer bend) and IV (flowdivider). Of the cross-sections 88% had plaque. Of all parts I, 72% contained plaque. This was 62%, 38% and 31% in parts II, III and IV. In cross-sections with only 1 or 2 parts inflicted, plaque was found in part I and/or II in 94%. In 93% of the cross-sections with the flowdivider inflicted, parts I and/or II were also inflicted. Plaque was never found exclusively in the flowdivider part IV. Conclusions: We demonstrated that plaque is mostly present in low WSS regions, whereas plaque in high WSS regions is accompanied by plaque in adjacent low WSS regions. It is therefore plausible that plaque grows from the outer wall (low WSS) of the bifurcation towards the flowdivider (high WSS).

There is ample evidence that the development of acute coronary syndrome is linked to the presence of lipid-core, necrotic plaque. However, there is little information on the natural history of lipid-core plaques in humans. A close link between structural changes of atherosclerotic plaques over time to the local shear stress conditions in the arterial system has been reported.1 Although low shear stress is recognized for its proatherogenic impact on the endothelium,1 its role in plaque composition, destabilization, and rupture is less clear. The current paradigm postulates that low shear stress is a necessary condition for plaque accumulation. However, once lumen narrowing occurs because of plaque, local shear stress increases.2 We describe an approach that allows studying the interaction of lipid-core plaque accumulation and local shear stress in a correct anatomic 3D reconstruction of coronary arteries in living patients. A 61-year-old man with a history of myocardial infarction and stenting of the right coronary …