Progressive Attenuation of the Longitudinal Kinetics in the Common Carotid Artery: Preliminary in Vivo Assessment

Longitudinal kinetics (LOKI) of the arterial wall consists of the shearing motion of the intima-media complex over the adventitia layer in the direction parallel to the blood flow during the cardiac cycle. The aim of this study was to investigate the local variability of LOKI amplitude along the length of the vessel. By use of a previously validated motion-estimation framework, 35 in vivo longitudinal B-mode ultrasound cine loops of healthy common carotid arteries were analyzed. Results indicated that LOKI amplitude is progressively attenuated along the length of the artery, as it is larger in regions located on the proximal side of the image (i.e., toward the heart) and smaller in regions located on the distal side of the image (i.e., toward the head), with an average attenuation coefficient of −2.5 ± 2.0%/mm. Reported for the first time in this study, this phenomenon is likely to be of great importance in improving understanding of atherosclerosis mechanisms, and has the potential to be a novel index of arterial stiffness

Estimation de paramètres mécaniques de la paroi carotidienne par imagerie ultrasonore in vivo pour la détection précoce de comportements pathologiques

National audienceLes maladies cardiovasculaires représentent la première cause de mortalité dans les pays industrialisés. Il est donc important d'effectuer un diagnostic précoce, préférentiellement de manière non invasive, pour traiter une vaste population. Les propriétés mécaniques des artères, notamment la carotide, sont affectées par l'athérosclérose, et sont considérées comme de bons indicateurs d'une manifestation pathologique précoce. Le comportement de la paroi de la carotide au long du cycle cardiaque présente plusieurs phénomènes particuliers dont l'analyse par imagerie ultrasonore permet de remonter aux causes pathologiques. Ce travail s'intéresse à l'étude conjointe de ces paramètres mécaniques au long d'une séquence d'images échographiques. Nous considérons principalement la force de cisaillement longitudinale exercée par le sang sur la paroi, l'onde de pouls causée par l'effet de dilatation-contraction radiale, et la compression élastique des couches de l'artère. Notre approche trouve son originalité dans le fait qu'elle prend en compte conjointement plusieurs paramètres mécaniques obtenus in vivo et se destine prioritairement à une application clinique pratique pouvant fournir une aide au diagnostic. Les séquences d'images ultrasonores traitées sont des coupes longitudinales de la carotide commune acquises avec un échographe clinique. Nous effectuons une analyse spatio-temporelle en considérant que le mouvement de chaque point de la paroi est continu dans le temps et dans l'espace. Le déplacement est estimé précisément grâce à un algorithme de mise en correspondance de blocs déformables. En fonction des paramètres à estimer pour l'étude du déplacement des couches de la carotide, les tailles de blocs et de noyau utilisés sont déterminées de manière optimale. Un comportement pathologique peut finalement être détecté à partir des paramètres extraits en comparaison de la déformation attendue d'une artère saine

Estimation de paramètres mécaniques de la paroi carotidienne par imagerie ultrasonore in vivo pour la détection précoce de comportements pathologiques

National audienceLes maladies cardiovasculaires représentent la première cause de mortalité dans les pays industrialisés. Il est donc important d'effectuer un diagnostic précoce, préférentiellement de manière non invasive, pour traiter une vaste population. Les propriétés mécaniques des artères, notamment la carotide, sont affectées par l'athérosclérose, et sont considérées comme de bons indicateurs d'une manifestation pathologique précoce. Le comportement de la paroi de la carotide au long du cycle cardiaque présente plusieurs phénomènes particuliers dont l'analyse par imagerie ultrasonore permet de remonter aux causes pathologiques. Ce travail s'intéresse à l'étude conjointe de ces paramètres mécaniques au long d'une séquence d'images échographiques. Nous considérons principalement la force de cisaillement longitudinale exercée par le sang sur la paroi, l'onde de pouls causée par l'effet de dilatation-contraction radiale, et la compression élastique des couches de l'artère. Notre approche trouve son originalité dans le fait qu'elle prend en compte conjointement plusieurs paramètres mécaniques obtenus in vivo et se destine prioritairement à une application clinique pratique pouvant fournir une aide au diagnostic. Les séquences d'images ultrasonores traitées sont des coupes longitudinales de la carotide commune acquises avec un échographe clinique. Nous effectuons une analyse spatio-temporelle en considérant que le mouvement de chaque point de la paroi est continu dans le temps et dans l'espace. Le déplacement est estimé précisément grâce à un algorithme de mise en correspondance de blocs déformables. En fonction des paramètres à estimer pour l'étude du déplacement des couches de la carotide, les tailles de blocs et de noyau utilisés sont déterminées de manière optimale. Un comportement pathologique peut finalement être détecté à partir des paramètres extraits en comparaison de la déformation attendue d'une artère saine

Progressive Attenuation of the Longitudinal Kinetics in the Common Carotid Artery: Preliminary in Vivo Assessment

International audienceLongitudinal kinetics (LOKI) of the arterial wall consists of the shearing motion of the intima–media complex over the adventitia layer in the direction parallel to the blood flow during the cardiac cycle. The aim of this study was to investigate the local variability of LOKI amplitude along the length of the vessel. By use of a previously validated motion-estimation framework, 35 in vivo longitudinal B-mode ultrasound cine loops of healthy common carotid arteries were analyzed. Results indicated that LOKI amplitude is progressively attenuated along the length of the artery, as it is larger in regions located on the proximal side of the image (i.e., toward the heart) and smaller in regions located on the distal side of the image (i.e., toward the head), with an average attenuation coefficient of −2.5 ± 2.0%/mm. Reported for the first time in this study, this phenomenon is likely to be of great importance in improving understanding of atherosclerosis mechanisms, and has the potential to be a novel index of arterial stiffness

Tracking arterial wall motion in a 2D+t volume

International audienceThe aim of this study is to propose a motion tracking framework dedicated to estimate the trajectory of the common carotid artery wall in B-mode ultrasound sequences. As the image quality of routinely acquired scans is often degraded by a number of factors, accurate estimation of the tissues motion is a challenging task. To address this issue, the main feature of our method is the research of an optimal a posteriori solution, which is computed using a dynamic programming scheme once all frames have been processed. Applied in vivo on 15 healthy volunteers, our method showed an overall good tracking performance, with an average absolute tracking error of 104 ± 127 μm and 29 ± 57 μm, in the longitudinal and radial directions, respectively. This work has potential to improve motion estimation in ultrasound imaging, and could contribute to provide more reliable information about vascular health in a clinical setting

Pattern Analysis of the Kinematics in Ultrasound Videos of the Common Carotid Artery – Application to Cardiovascular Risk Evaluation

International audienceThe clinical context of this study is the prediction of cardiovascular risk by analyzing ultrasound images of the common carotid artery. The principal methodological contribution of the present work is the implementation of image processing algorithms to characterize the pattern of the artery-wall spatio-temporal trajectory during the cardiac cycle. Normalized signals corresponding to the trajectory of the biological tissues were gathered via an initial phase of motion tracking based on Kalman filtering. The originality of the present work is the introduction of three complementary statistical approaches to interrogate these signals. First, a Machine Learning strategy was carried out with the AdaBoost algorithm to automatically identify healthy and at-risk subjects. Second, the Dynamic Time Wrapping method was applied to measure the pairwise similarity between signals and identify clusters. Third, a Principal Component Analysis was performed to randomly generate unseen patterns using Point Distribution Modeling. A total of 84 subjects (42 healthy volunteers and 42 at-risk patients) were involved in this study. Two significantly different profile archetypes could be reconstructed from the two populations, showing the effect of the atherosclerosis pathology on the artery. Results demonstrate that the healthy and at-risk signals can successfully be classified with an accuracy of 73%. Quantification of the pairwise distance between all signals indicated that healthy patterns are more similar to each other, whereas there is a wider variability between at-risk patterns. Finally, new signals were generated using a statistical model, possibly hinting towards new patterns characteristics

A fully-automatic method to segment the carotid artery layers in ultrasound imaging: Application to quantify the compression-decompression pattern of the intima-media complex during the cardiac cycle

International audienceThe aim of this study was to introduce and evaluate a contour segmentation method to extract the interfaces of the intima–media complex in carotid B-mode ultrasound images. The method was applied to assess the temporal variation of intima–media thickness during the cardiac cycle. The main methodological contribution of the proposed approach is the introduction of an augmented dimension to process 2-D images in a 3-D space. The third dimension, which is added to the two spatial dimensions of the image, corresponds to the tentative local thickness of the intima–media complex. The method is based on a dynamic programming scheme that runs in a 3-D space generated with a shape-adapted filter bank. The optimal solution corresponds to a single medial axis representation that fully describes the two anatomical interfaces of the arterial wall. The method is fully automatic and does not require any input from the user. The method was trained on 60 subjects and validated on 184 other subjects from six different cohorts and four different medical centers. The arterial wall was successfully segmented in all analyzed images (average pixel size = 57 ± 20 mm), with average segmentation errors of 47 ± 70 mm for the lumen–intima interface, 55 ± 68 mm for the media–adventitia interface and 66 ± 90 mm for the intima–media thickness. The amplitude of the temporal variations in IMT during the cardiac cycle was significantly higher in the diseased population than in healthy volunteers (106 ± 48 vs. 86 ± 34 mm, p = 0.001). The introduced framework is a promising approach to investigate an emerging functional parameter of the arterial wall by assessing the cyclic compression–decompression pattern of the tissues

Carotid Wall Longitudinal Motion in Ultrasound Imaging: An Expert Consensus Review

International audienceMotion extracted from the carotid artery wall provides unique information for vascular health evaluation. Carotid artery longitudinal wall motion corresponds to the multiphasic arterial wall excursion in the direction parallel to blood flow during the cardiac cycle. While this motion phenomenon has been well characterized, there is a general lack of awareness regarding its implications for vascular health assessment or even basic vascular physiology. In the last decade, novel estimation strategies and clinical investigations have greatly advanced our understanding of the bi-axial behavior of the carotid artery, necessitating an up-to-date review to summarize and classify the published literature in collaboration with technical and clinical experts in the field. Within this review, the state-of-the-art methodologies for carotid wall motion estimation are described, and the observed relationships between longitudinal motion-derived indices and vascular health are reported. The vast number of studies describing the longitudinal motion pattern in plaque-free arteries, with its putative application to cardiovascular disease prediction, point to the need for characterizing the added value and applicability of longitudinal motion beyond established biomarkers. To this aim, the main purpose of this review was to provide a strong base of theoretical knowledge, together with a curated set of practical guidelines and recommendations for longitudinal motion estimation in patients, to foster future discoveries in the field, toward the integration of longitudinal motion in basic science as well as clinical practice