32 research outputs found
Association entre l'Ă©lastographie vasculaire non invasive et l'indice de masse corporelle chez les enfants
Sachant que lâAthĂ©rosclĂ©rose commence durant lâenfance par des marqueurs subcliniques, cette Ă©tude explore lâassociation entre lâindice de masse corporelle (IMC) et lâĂ©lastographie vasculaire non-invasive (NIVE) des artĂšres carotides communes chez les enfants. On compare aussi les techniques de mesure de lâintima-mĂ©dia (IMT) des artĂšres carotides en se basant sur le mode-B et la radiofrĂ©quence (RF) chez les enfants avec IMC normal et Ă©levĂ©. Il sâagit dâune Ă©tude prospective effectuĂ©e entre 2005 et 2011. Les paramĂštres de « NIVE » ont Ă©tĂ© comparĂ©s pour deux groupes dâIMC (normal et Ă©levĂ©) de 60 enfants respectivement, faisant tous partie de la cohorte de lâĂ©tude QUebec Adipose and Lifestyle Investigation in Youth (QUALITY). Les paramĂštres de NIVE incluent la contrainte axiale cumulative (CAS) en %, la translation axiale cumulative (CAT) en mm. LâĂ©paisseur de lâintima-mĂ©dia est calculĂ©e selon trois mĂ©thodes : logiciel «Mâath-Std» (mode-B), « echotracking » des signaux de RF et probabilitĂ© de distribution des signaux de RF sur la plateforme NIVE. Une analyse ANOVA et corrĂ©lation Pearson ont Ă©tĂ© effectuĂ©es sur le logiciel SAS version 9.3. Une corrĂ©lation intra-class (ICC) a Ă©tĂ© effectuĂ©e sur un logiciel MedCalc version 17.2. LâĂąge moyen Ă©tait 11,4 ans pour le groupe IMC normal et 12 pour le groupe IMC Ă©levĂ©. Cinquante-huit pourcent Ă©taient des garçons dans le groupe IMC normal et 63% dans le groupe IMC Ă©levĂ©. Les deux groupes Ă©taient diffĂ©rents selon lâĂąge, stade de Tanner, tension artĂ©rielle (systolique et diastolique), et LDL mais similaire pour le sexe. En contrĂŽlant pour les variables confondantes, la CAS nâest pas diffĂ©rente entre les deux groupes. La CAT est plus basse chez les enfants avec IMC normal (CAT=0.51 +/-0.17 mm pour le groupe « IMC normal » et 0.67+/-0.24 mm pour le groupe « IMC Ă©levĂ© » (p<0.001)). Il y a une trĂšs faible corrĂ©lation entre les trois techniques de mesure dâIMT ICC=0,34 (95% intervalle de confiance 0,27-0,39). LâIMT est significativement plus Ă©levĂ© dans le groupe dâenfants « IMC Ă©levĂ© ». Mode-B (0.55 mm « IMC normal » vs. 0.57 mm « IMC Ă©levĂ© »; p=0.02); IMT RF (0.45 mm « IMC normal » vs. 0.48 mm « IMC Ă©levĂ© »; p=0.03) et IMT probabilitĂ© de distribution des signaux RF (0.32 mm « IMC normal » vs. 0.35 mm « IMC Ă©levĂ© »; p=0.010). La NIVE montre une diffĂ©rence significative dans la CAT de l'artĂšre carotide commune des enfants avec un IMC normal par rapport Ă l'IMC Ă©levĂ©. Des variations significatives de la mesure des IMT ont Ă©tĂ© observĂ©es entre les diffĂ©rentes techniques. Cependant, les enfants avec IMC Ă©levĂ© ont des valeurs IMT plus Ă©levĂ©es, indĂ©pendamment de la mĂ©thode utilisĂ©e. Les deux marqueurs subcliniques peuvent ĂȘtre utilisĂ©s pour la stratification des enfants Ă risque de maladies cardiovasculaires. La mĂȘme mĂ©thode devrait toujours ĂȘtre utilisĂ©e.Knowing that cardiovascular disease risk factors are present in asymptomatic children, this study explores the association between non-invasive vascular elastography (NIVE) as a subclinical marker of atherosclerosis and obesity in children. In the absence of a gold standard, we also compare B-mode and Radiofrequency (RF) based ultrasound measurements of intima-media thickness (IMT) in children with normal and increased body mass index (BMI). This is a prospective study between 2005 and 2011. NIVE parameters and IMT of the common carotid artery were compared between 60 children with normal BMI and 60 children with increased BMI enrolled in the QUebec Adipose and Lifestyle Investigation in Youth cohort (QUALITY). NIVE parameters included cumulated axial strain (CAS) (%) and cumulated axial translation (CAT) in mm. The three methods of IMT measurements included Mâath Std (B-mode), RF echotracking system and RF probability distribution using NIVE platform. ANOVA analysis and Pearson correlation were calculated using SAS version 9.3. Intra-class correlation coefficient (ICC) and regression analysis was done on MedCalc software version 17.2. The mean age was 11.4 years for the normal BMI group and 12 years for the increased BMI group. Fifty-eight percent were boys in the normal BMI group and 63% in the increased BMI group. The two groups were significantly different with respect to age, Tanner stage, systolic and diastolic blood pressure and were similar with respect to sex. After controlling for confounders, the results show no difference in CAS between the two groups and a significantly lower CAT in the normal BMI group (CAT=0.51+/-0.17 mm for the normal BMI group and 0.67+/-0.24 mm for the increased BMI group (p<0.001)). There is a weak correlation among the three techniques. ICC=0.34 (95% confidence interval (CI): 0.27-0.39). There is however significantly increased IMT in children with increased BMI according to all three techniques. The results were as follow: for B-mode IMT (0.55 mm (normal BMI group) vs. 0.57 mm (increased BMI group); p=0.02); for RF echotracking IMT (0.45 mm (normal BMI group) vs. 0.48 mm (increased BMI group); p=0.03) and for RF probability distribution IMT (0.32 mm (normal BMI group) vs. 0.35 mm (increased BMI group); p=0.010).NIVE is a one-step technique for IMT and CAT measurement in children at risk. Significant IMT measurement variation is observed between the three techniques. However, children with increased BMI tend to have higher IMT values regardless of the technique. Both subclinical markers can be used for optimal stratification of children with cardiovascular disease risk factors. The same technique should be used throughout
Segmentation of skin lesions in 2D and 3D ultrasound images using a spatially coherent generalized Rayleigh mixture model
This paper addresses the problem of jointly estimating the statistical distribution and segmenting lesions in multiple-tissue high-frequency skin ultrasound images. The distribution of multiple-tissue images is modeled as a spatially coherent finite mixture of heavy-tailed Rayleigh distributions. Spatial coherence inherent to biological tissues is modeled by enforcing local dependence between the mixture components. An original Bayesian algorithm combined with a Markov chain Monte Carlo method is then proposed to jointly estimate the mixture parameters and a label-vector associating each voxel to a tissue. More precisely, a hybrid Metropolis-within-Gibbs sampler is used to draw samples that are asymptotically distributed according to the posterior distribution of the Bayesian model. The Bayesian estimators of the model parameters are then computed from the generated samples. Simulation results are conducted on synthetic data to illustrate the performance of the proposed estimation strategy. The method is then successfully applied to the segmentation of in vivo skin tumors in high-frequency 2-D and 3-D ultrasound images
Constrained snake vs. conventional snake for carotid ultrasound automated IMT measurements on multi-center data sets
Accurate intima-media thickness (IMT) measurement of the carotid artery from minimal plaque ultrasound images is a relevant clinical need, since IMT increase is related to the progression of atherosclerosis. In this paper, we describe a novel dual snake-based model for the high-performance carotid IMT measurement, called Carotid Measurement Using Dual Snakes (CMUDS). Snakes (which are deformable contours) adapt to the lumen-intima (LI) and media-adventitia (MA) interfaces, thus enabling the IMT computation as distance between the LI and MA snakes. However, traditional snakes might be unable to maintain a correct distance and in some spatial location along the artery, it might even collapse between them or diverge. The technical improvement of this work is the definition of a dual snake-based constrained system, which prevents the LI and MA snakes from collapsing or bleeding, thus optimizing the IMT estimation. The CMUDS system consists of two parametric models automatically initialized using the far adventitia border which we automatically traced by using a previously developed multi-resolution approach. The dual snakes evolve simultaneously and are constrained by the distances between them, ensuring the regularization of LI/MA topology. We benchmarked our automated CMUDS with the previous conventional semi-automated snake system called Carotid Measurement Using Single Snake (CMUSS). Two independent readers manually traced the LIMA boundaries of a multi-institutional, multi-ethnic, and multi-scanner database of 665 CCA longitudinal 2D images. We evaluated our system performance by comparing it with the gold standard as traced by clinical readers. CMUDS and CMUSS correctly processed 100% of the 665 images. Comparing the performance with respect to the two readers, our automatically measured IMT was on average very close to that of the two readers (IMT measurement biases for CMUSS was equal to â0.011 ± 0.329 mm and â0.045 ± 0.317 mm, respectively, while for CMUDS, it was 0.030 ± 0.284 mm and â0.004 ± 0.273 mm, respectively). The Figure-of-Merit of the system was 98.5% and 94.4% for CMUSS, while 96.0% and 99.6% for CMUDS, respectively. Results showed that the dual-snake system CMUDS reduced the IMT measurement error accuracy (Wilcoxon, p < 0.02) and the IMT error variability (Fisher, p < 3 Ă 10â2). We propose the CMUDS technique for use in large multi-centric studies, where the need for a standard, accurate, and automated IMT measurement technique is require
An automatic 2D CAD algorithm for the segmentation of the IMT in ultrasound carotid artery images
Common carotid intima-media thickness (IMT) is a reliable measure of early atherosclerosis - its accurate measurement can be used in the process of evaluating the presence and tracking the progression of disease. The aim of this study is to introduce a novel unsupervised Computer Aided Detection (CAD) algorithm that is able to identify and measure the IMT in 2D ultrasound carotid images. The developed technique relies on a suite of image processing algorithms that embeds a statistical model to identify the two interfaces that form the IMT without any user intervention. The proposed image segmentation scheme is based on a spatially continuous vascular model and consists of several steps including data preprocessing, edge filtering, model selection, edge reconstruction and data refinement. To conduct a quantitative evaluation each image was manually segmented by clinical experts and performance metrics between the segmentation results obtained by the proposed method and the ground truth data were calculated. The experimental results show that the proposed CAD system is robust in accurately estimating the IMT in ultrasound carotid data
Fully automated segmentation and tracking of the intima media thickness in ultrasound video sequences of the common carotid artery
AbstractâThe robust identification and measurement of the intima media thickness (IMT) has a high clinical relevance because it represents one of the most precise predictors used in the assessment of potential future cardiovascular events. To facilitate the analysis of arterial wall thickening in serial clinical investigations, in this paper we have developed a novel fully automatic algorithm for the segmentation, measurement, and tracking of the intima media complex (IMC) in B-mode ultrasound video sequences. The proposed algorithm entails a two-stage image analysis process that initially addresses the segmentation of the IMC in the first frame of the ultrasound video sequence using a model-based approach; in the second step, a novel customized tracking procedure is applied to robustly detect the IMC in the subsequent frames. For the video tracking procedure, we introduce a spatially coherent algorithm called adaptive normalized correlation that prevents the tracking process from converging to wrong arterial interfaces. This represents the main contribution of this paper and was developed to deal with inconsistencies in the appearance of the IMC over the cardiac cycle. The quantitative evaluation has been carried out on 40 ultrasound video sequences of the common carotid artery (CCA) by comparing the results returned by the developed algorithm with respect to ground truth data that has been manually annotated by clinical experts. The measured IMTmean ± standard deviation recorded by the proposed algorithm is 0.60 mm ± 0.10, with a mean coefficient of variation (CV) of 2.05%, whereas the corresponding result obtained for the manually annotated ground truth data is 0.60 mm ± 0.11 with a mean CV equal to 5.60%. The numerical results reported in this paper indicate that the proposed algorithm is able to correctly segment and track the IMC in ultrasound CCA video sequences, and we were encouraged by the stability of our technique when applied to data captured under different imaging conditions. Future clinical studies will focus on the evaluation of patients that are affected by advanced cardiovascular conditions such as focal thickening and arterial plaques
Automatic location of atherosclerotic plaques by ultrasounds
Dissertação de Mestrado em Engenharia BiomĂ©dica apresentada Ă Faculdade de CiĂȘncias e Tecnologia da Universidade de Coimbra.As doenças cardiovasculares sĂŁo uma das mais importantes causas de morte em todo o mundo. Em particular, a aterosclerose Ă© uma doença difĂcil de diagnosticar em fases iniciais e hĂĄ uma necessidade urgente de novas tĂ©cnicas para diagnosticar pacientes em risco baseadas na medição espessura do complexo intima-media.
Este trabalho procura desenvolver um novo sistema de segmentação para a detecção da espessura do complexo intima-media em artĂ©rias carĂłtida. Todas as images foram prĂ©-processadas de forma a remover o efeito do ruĂdo espectral, e a regiĂŁo de interesse Ă© automaticamente selecionada usando thresholding e connected-component analysis. O sistema baseia-se na derivada de primeira ordem da função Gaussiana como detector das estruturas desejadas â interfaces lumen-intima e media-adventitia, cuja distĂąncia entre eles corresponde Ă espessura do complexo intima-media.
Os valores obtido foram comparados com mediçÔes realizadas por um especialista. Em média, a diferença entre mediçÔes não se mostrou significante mas o seu desvio-padrão associado pode impedir a aplicação em situação médica.
Palavras-chave: Ultrasons, Artéria Carótida, Aterosclerose, Segmentação, Intima, Media, Adventitia
Classification approach for diagnosis of arteriosclerosis using B-mode ultrasound carotid images
Tese de mestrado. Engenharia Biomédica. Faculdade de Engenharia. Universidade do Porto. 201