Computers 25 coefficient 0.86 from the map set.The optimal ANN configuration was with 3 neurons i... more Computers 25 coefficient 0.86 from the map set.The optimal ANN configuration was with 3 neurons in the hidden layer.The difference among the three ROC curves resulted statistically significant. Conclusions: An ANN-based CPR performs better in the clinical prediction of PE than classical rulers without increasing the number of items required for the analysis.
The International Journal of Cardiovascular Imaging, 2014
Intravascular ultrasound (IVUS)-based reconstructions have been traditionally used to examine the... more Intravascular ultrasound (IVUS)-based reconstructions have been traditionally used to examine the effect of endothelial shear stress (ESS) on neointimal formation. The aim of this analysis is to compare the association between ESS and neointimal thickness (NT) in models obtained by the fusion of optical coherence tomography (OCT) and coronary angiography and in the reconstructions derived by the integration of IVUS and coronary angiography. We analyzed data from six patients implanted with an Absorb bioresorbable vascular scaffold that had biplane angiography, IVUS and OCT investigation at baseline and 6 or 12 months follow-up. The IVUS and OCT follow-up data were fused separately with the angiographic data to reconstruct the luminal morphology at baseline and follow-up. Blood flow simulation was performed on the baseline reconstructions and the ESS was related to NT. In the OCT-based reconstructions the ESS were lower compared to the IVUS-based models (1.29 ± 0.66 vs. 1.87 ± 0.66 Pa, P = 0.030). An inverse correlation was noted between the logarithmic transformed ESS and the measured NT in all the OCT-based models which was higher than the correlation reported in five of the six IVUS-derived models (-0.52 ± 0.19 Pa vs.-0.10 ± 0.04, P = 0.028). Fusion of OCT and coronary angiography appears superior to IVUS-based reconstructions; therefore it should be the method of choice for the study of the effect of the ESS on neointimal proliferation.
2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2013
Low density lipoprotein (LDL) has a significant role on the atherosclerotic plaque development, w... more Low density lipoprotein (LDL) has a significant role on the atherosclerotic plaque development, while the concentration of high density lipoproteins (HDL) is considered to play an atheroprotective role according to several biochemical mechanisms. In this work, it is the first time that both LDL and HDL concentrations are taken into account in order to predict the regions prone for plaque development. Our modeling approach is based on the use of a realistic three-dimensional reconstructed pig coronary artery in two time points. Biochemical data measured in the pig were also included in order to develop a more customized model. We modeled coronary blood flow by solving the Navier-Stokes equations in the arterial lumen and plasma filtration in the arterial wall using Darcy's Law. HDL transport was modeled only in the arterial lumen using the convection-diffusion equation, while LDL transport was modeled both in the lumen and the arterial wall. An additional novelty of this work is that we model the oxidation of LDL taking into account the atheroprotective role of HDL. The results of our model were in good agreement with histological findings demonstrating that increased oxidized LDL is found near regions of advanced plaques, while non-oxidized LDL is found in regions of early plaque types.
European heart journal cardiovascular Imaging, Jan 17, 2018
To examine the efficacy of angiography derived endothelial shear stress (ESS) in predicting ather... more To examine the efficacy of angiography derived endothelial shear stress (ESS) in predicting atherosclerotic disease progression. Thirty-five patients admitted with ST-elevation myocardial infarction that had three-vessel intravascular ultrasound (IVUS) immediately after revascularization and at 13 months follow-up were included. Three dimensional (3D) reconstruction of the non-culprit vessels were performed using (i) quantitative coronary angiography (QCA) and (ii) methodology involving fusion of IVUS and biplane angiography. In both models, blood flow simulation was performed and the minimum predominant ESS was estimated in 3 mm segments. Baseline plaque characteristics and ESS were used to identify predictors of atherosclerotic disease progression defied as plaque area increase and lumen reduction at follow-up. Fifty-four vessels were included in the final analysis. A moderate correlation was noted between ESS estimated in the 3D QCA and the IVUS-derived models (r = 0.588, P < ...
Purpose: To study the dose and time effect of external beam irradiation on the morphometry of bot... more Purpose: To study the dose and time effect of external beam irradiation on the morphometry of both angioplasted and nonangioplasted arteries in a hypercholesterolemic rabbit model. Methods and materials: Eight groups of rabbit femoral arteries were studied: arteries (a) with no intervention, (b) irradiated with a 12-Gy 6 MV X-ray dose, (c) with a 18-Gy, (d) treated with balloon angioplasty,
2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2013
Optical Coherence Tomography (OCT) is a new invasive technology for performing high-resolution cr... more Optical Coherence Tomography (OCT) is a new invasive technology for performing high-resolution crosssectional imaging of the coronary arteries. In OCT images only Calcified plaque (CA) components can be accurately depicted as light penetrates hard tissue. In this work we present an automated method for detecting CA in OCT images. The method is fully automated as no user intervention is needed and includes three steps. In the first step the region between the lumen and the maximum penetration depth of OCT from the lumen border is determined. In the second step the region is classified into 3 clusters using the K-means algorithm. CA is identified using the results of k-means. The method was validated using H[SHUWV ¶ annotations on 27 images. The sensitivity of the method is 83% with Positive predictive value (PVV) 74 %. I. INTRODUCTION oronary optical coherence tomography [1,2] is a relatively new imaging modality which was introduced to overcome the limitation of previous coronary imaging techniques. In contrast to intravascular ultrasound (IVUS), that is based on tissue sound reflection, OCT is based on the analysis of the reflected light allowing visualization of intra-coronary features with a higher analysis [3,4]. However, light cannot penetrate tissue as sound does, therefore OCT has one drawback, its limited penetration depth (2-3.5mm) [5]. The OCT imaging ability is limited in This research project has been co-financed by the European Union
Heart failure (HF) is a chronic disease associated with significant prevalence, mortality, and he... more Heart failure (HF) is a chronic disease associated with significant prevalence, mortality, and health care expenditure. The aim of the present study was to explore the factors associated with anxiety and depression experienced by patients hospitalized with HF. We evaluated 190 hospitalized HF patients in four public hospitals. The data were collected using a specific questionnaire, which, apart from demographic and clinical variables, included the Hospital Anxiety and Depression Scale (HADS). In the total sample, 24.7% and 32.6% of patients were found to have moderate or high levels of anxiety, respectively. Simple multinomial logistic regression showed that no characteristic was significantly associated with anxiety. It also appeared that 17.4% of patients had minor and 24.2% major depression. Among the factors examined, longer disease duration was associated with a higher probability of being depressed (p=0.041). Moreover, single/divorced and widowed patients were more likely to have major depression compared to married patients (35.6% vs. 19.2%, p=0.046). Simple multinomial logistic regression revealed that married patients were 59% less likely to have major depression compared to their unmarried counterparts (OR: 0.41). Moreover, patients with short (&amp;amp;amp;amp;amp;amp;amp;amp;lt;1 year) and moderate (2-5 years) disease duration were 69% (OR: 0.31) and 61% (OR: 0.39) less likely to have major depression compared to those with a long disease duration. Multiple multinomial logistic regression showed that only the disease duration remained statistically significantly associated with depression after controlling for the rest of factors found to be significant at a univariate level. Nurses and physicians must take measures for the identification, assessment and management of anxiety and depression in this clinical population.
Advanced Topics in Scattering Theory and Biomedical Engineering - 9th International Workshop on Mathematical Methods in Scattering Theory and Biomedical Engineering, 2010
Hellenic journal of cardiology: HJC = Hellēnikē kardiologikē epitheōrēsē
A theromatous disease is still the prime cause of morbidity and mortality in most western societi... more A theromatous disease is still the prime cause of morbidity and mortality in most western societies. A severe degree of atheromatous disease impedes blood flow, creating significant problems in various organs (e.g. myocardial ischaemia, myocardial infarction, cerebral ischaemia, etc.). In spite of the systemic nature of the risk factors related with atheromatosis (hypertension, hyperlipidaemia, diabetes mellitus), atheromatous disease is a site-specific disease with a tendency to develop in certain regions of the arteries: for example, at the outer wall of bifurcations or at the inner wall of arteries with a significant degree of curvature. For half a century now, haemodynamic forces have been proposed as factors controlling the structure of vessels (vascular wall remodelling) and the development of vascular pathology (onset and progression of atheromatous disease). 1-3
The Low Density Lipoprotein (LDL) accumulation is the major factor which affects atherosclerosis ... more The Low Density Lipoprotein (LDL) accumulation is the major factor which affects atherosclerosis during its early stages. Endothelial permeability is also influenced by local wall shear stresses. This phenomenon increases the water and macromolecule transport from the artery lumen to the artery wall. This paper presents a computational model of LDL transport from the arterial lumen to the arterial wall. More specifically, we investigate the blood flow dependent LDL transfer in a carotid artery bifurcation. The blood flow is modeled using the Navier-Stokes equations and the Darcy's law is employed to study the transmural flow in the porous artery wall. The mass transfer problem is solved using the convection -diffusion equations. The combined fluid dynamics and mass transfer equations are based on volume flux and solute flux calculated using the Kedem -Katchalsky equations. The endothelial permeability and hydraulic conductivity depend on the shear stress. The numerical solution of the above equations is obtained using the finite element method. Our results confirm what the experimental studies report that LDL accumulation is achieved in artery regions where low shear stresses exist. In particular, in our model we observe elevated LDL aggregation in areas where the wall shear stress is lower than 2 Pa. Also the increase of LDL concentration occurs in a thin layer close to the artery wall at the outer parts of artery segments, which also agrees with the experimental observation. In addition, we concluded that shear stress affects the transport of macromolecules from the blood to the carotid artery wall.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2012
The aim of this study is to describe a new method for three-dimensional (3D) reconstruction of co... more The aim of this study is to describe a new method for three-dimensional (3D) reconstruction of coronary arteries using Frequency Domain Optical Coherence Tomography (FD-OCT) images. The rationale is to fuse the information about the curvature of the artery, derived from biplane angiographies, with the information regarding the lumen wall, which is produced from the FD-OCT examination. The method is based on a three step approach. In the first step the lumen borders in FD-OCT images are detected. In the second step a 3D curve is produced using the center line of the vessel from the two biplane projections. Finally in the third step the detected lumen borders are placed perpendicularly onto the path based on the centroid of each lumen border. The result is a 3D reconstructed artery produced by all the lumen borders of the FD-OCT pullback representing the 3D arterial geometry of the vessel.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011
Optical Coherence Tomography (OCT) is a fiber--optic imaging modality which produces high resolut... more Optical Coherence Tomography (OCT) is a fiber--optic imaging modality which produces high resolution tomographic images of the coronary lumen and outer vessel wall. While OCT images present morphological information in highly resolved detail, the characterization of the various plaque components relies on trained readers. The aim of this study is to extract a set of features in grayscale OCT images and to use them in order to classify the atherosclerotic plaque. Intensity and texture based features we used in order to classify the plaque in four plaque types: Calcium (C), Lipid Pool (LP), Fibrous Tissue (FT) and Mixed Plaque (MP). 50 OCT annotated images from 3 patients were used to train and test the proposed plaque characterization method. Using a Random Forests classifier overall classification accuracy 80.41% is reported.
Computers 25 coefficient 0.86 from the map set.The optimal ANN configuration was with 3 neurons i... more Computers 25 coefficient 0.86 from the map set.The optimal ANN configuration was with 3 neurons in the hidden layer.The difference among the three ROC curves resulted statistically significant. Conclusions: An ANN-based CPR performs better in the clinical prediction of PE than classical rulers without increasing the number of items required for the analysis.
The International Journal of Cardiovascular Imaging, 2014
Intravascular ultrasound (IVUS)-based reconstructions have been traditionally used to examine the... more Intravascular ultrasound (IVUS)-based reconstructions have been traditionally used to examine the effect of endothelial shear stress (ESS) on neointimal formation. The aim of this analysis is to compare the association between ESS and neointimal thickness (NT) in models obtained by the fusion of optical coherence tomography (OCT) and coronary angiography and in the reconstructions derived by the integration of IVUS and coronary angiography. We analyzed data from six patients implanted with an Absorb bioresorbable vascular scaffold that had biplane angiography, IVUS and OCT investigation at baseline and 6 or 12 months follow-up. The IVUS and OCT follow-up data were fused separately with the angiographic data to reconstruct the luminal morphology at baseline and follow-up. Blood flow simulation was performed on the baseline reconstructions and the ESS was related to NT. In the OCT-based reconstructions the ESS were lower compared to the IVUS-based models (1.29 ± 0.66 vs. 1.87 ± 0.66 Pa, P = 0.030). An inverse correlation was noted between the logarithmic transformed ESS and the measured NT in all the OCT-based models which was higher than the correlation reported in five of the six IVUS-derived models (-0.52 ± 0.19 Pa vs.-0.10 ± 0.04, P = 0.028). Fusion of OCT and coronary angiography appears superior to IVUS-based reconstructions; therefore it should be the method of choice for the study of the effect of the ESS on neointimal proliferation.
2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2013
Low density lipoprotein (LDL) has a significant role on the atherosclerotic plaque development, w... more Low density lipoprotein (LDL) has a significant role on the atherosclerotic plaque development, while the concentration of high density lipoproteins (HDL) is considered to play an atheroprotective role according to several biochemical mechanisms. In this work, it is the first time that both LDL and HDL concentrations are taken into account in order to predict the regions prone for plaque development. Our modeling approach is based on the use of a realistic three-dimensional reconstructed pig coronary artery in two time points. Biochemical data measured in the pig were also included in order to develop a more customized model. We modeled coronary blood flow by solving the Navier-Stokes equations in the arterial lumen and plasma filtration in the arterial wall using Darcy&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Law. HDL transport was modeled only in the arterial lumen using the convection-diffusion equation, while LDL transport was modeled both in the lumen and the arterial wall. An additional novelty of this work is that we model the oxidation of LDL taking into account the atheroprotective role of HDL. The results of our model were in good agreement with histological findings demonstrating that increased oxidized LDL is found near regions of advanced plaques, while non-oxidized LDL is found in regions of early plaque types.
European heart journal cardiovascular Imaging, Jan 17, 2018
To examine the efficacy of angiography derived endothelial shear stress (ESS) in predicting ather... more To examine the efficacy of angiography derived endothelial shear stress (ESS) in predicting atherosclerotic disease progression. Thirty-five patients admitted with ST-elevation myocardial infarction that had three-vessel intravascular ultrasound (IVUS) immediately after revascularization and at 13 months follow-up were included. Three dimensional (3D) reconstruction of the non-culprit vessels were performed using (i) quantitative coronary angiography (QCA) and (ii) methodology involving fusion of IVUS and biplane angiography. In both models, blood flow simulation was performed and the minimum predominant ESS was estimated in 3 mm segments. Baseline plaque characteristics and ESS were used to identify predictors of atherosclerotic disease progression defied as plaque area increase and lumen reduction at follow-up. Fifty-four vessels were included in the final analysis. A moderate correlation was noted between ESS estimated in the 3D QCA and the IVUS-derived models (r = 0.588, P < ...
Purpose: To study the dose and time effect of external beam irradiation on the morphometry of bot... more Purpose: To study the dose and time effect of external beam irradiation on the morphometry of both angioplasted and nonangioplasted arteries in a hypercholesterolemic rabbit model. Methods and materials: Eight groups of rabbit femoral arteries were studied: arteries (a) with no intervention, (b) irradiated with a 12-Gy 6 MV X-ray dose, (c) with a 18-Gy, (d) treated with balloon angioplasty,
2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2013
Optical Coherence Tomography (OCT) is a new invasive technology for performing high-resolution cr... more Optical Coherence Tomography (OCT) is a new invasive technology for performing high-resolution crosssectional imaging of the coronary arteries. In OCT images only Calcified plaque (CA) components can be accurately depicted as light penetrates hard tissue. In this work we present an automated method for detecting CA in OCT images. The method is fully automated as no user intervention is needed and includes three steps. In the first step the region between the lumen and the maximum penetration depth of OCT from the lumen border is determined. In the second step the region is classified into 3 clusters using the K-means algorithm. CA is identified using the results of k-means. The method was validated using H[SHUWV ¶ annotations on 27 images. The sensitivity of the method is 83% with Positive predictive value (PVV) 74 %. I. INTRODUCTION oronary optical coherence tomography [1,2] is a relatively new imaging modality which was introduced to overcome the limitation of previous coronary imaging techniques. In contrast to intravascular ultrasound (IVUS), that is based on tissue sound reflection, OCT is based on the analysis of the reflected light allowing visualization of intra-coronary features with a higher analysis [3,4]. However, light cannot penetrate tissue as sound does, therefore OCT has one drawback, its limited penetration depth (2-3.5mm) [5]. The OCT imaging ability is limited in This research project has been co-financed by the European Union
Heart failure (HF) is a chronic disease associated with significant prevalence, mortality, and he... more Heart failure (HF) is a chronic disease associated with significant prevalence, mortality, and health care expenditure. The aim of the present study was to explore the factors associated with anxiety and depression experienced by patients hospitalized with HF. We evaluated 190 hospitalized HF patients in four public hospitals. The data were collected using a specific questionnaire, which, apart from demographic and clinical variables, included the Hospital Anxiety and Depression Scale (HADS). In the total sample, 24.7% and 32.6% of patients were found to have moderate or high levels of anxiety, respectively. Simple multinomial logistic regression showed that no characteristic was significantly associated with anxiety. It also appeared that 17.4% of patients had minor and 24.2% major depression. Among the factors examined, longer disease duration was associated with a higher probability of being depressed (p=0.041). Moreover, single/divorced and widowed patients were more likely to have major depression compared to married patients (35.6% vs. 19.2%, p=0.046). Simple multinomial logistic regression revealed that married patients were 59% less likely to have major depression compared to their unmarried counterparts (OR: 0.41). Moreover, patients with short (&amp;amp;amp;amp;amp;amp;amp;amp;lt;1 year) and moderate (2-5 years) disease duration were 69% (OR: 0.31) and 61% (OR: 0.39) less likely to have major depression compared to those with a long disease duration. Multiple multinomial logistic regression showed that only the disease duration remained statistically significantly associated with depression after controlling for the rest of factors found to be significant at a univariate level. Nurses and physicians must take measures for the identification, assessment and management of anxiety and depression in this clinical population.
Advanced Topics in Scattering Theory and Biomedical Engineering - 9th International Workshop on Mathematical Methods in Scattering Theory and Biomedical Engineering, 2010
Hellenic journal of cardiology: HJC = Hellēnikē kardiologikē epitheōrēsē
A theromatous disease is still the prime cause of morbidity and mortality in most western societi... more A theromatous disease is still the prime cause of morbidity and mortality in most western societies. A severe degree of atheromatous disease impedes blood flow, creating significant problems in various organs (e.g. myocardial ischaemia, myocardial infarction, cerebral ischaemia, etc.). In spite of the systemic nature of the risk factors related with atheromatosis (hypertension, hyperlipidaemia, diabetes mellitus), atheromatous disease is a site-specific disease with a tendency to develop in certain regions of the arteries: for example, at the outer wall of bifurcations or at the inner wall of arteries with a significant degree of curvature. For half a century now, haemodynamic forces have been proposed as factors controlling the structure of vessels (vascular wall remodelling) and the development of vascular pathology (onset and progression of atheromatous disease). 1-3
The Low Density Lipoprotein (LDL) accumulation is the major factor which affects atherosclerosis ... more The Low Density Lipoprotein (LDL) accumulation is the major factor which affects atherosclerosis during its early stages. Endothelial permeability is also influenced by local wall shear stresses. This phenomenon increases the water and macromolecule transport from the artery lumen to the artery wall. This paper presents a computational model of LDL transport from the arterial lumen to the arterial wall. More specifically, we investigate the blood flow dependent LDL transfer in a carotid artery bifurcation. The blood flow is modeled using the Navier-Stokes equations and the Darcy's law is employed to study the transmural flow in the porous artery wall. The mass transfer problem is solved using the convection -diffusion equations. The combined fluid dynamics and mass transfer equations are based on volume flux and solute flux calculated using the Kedem -Katchalsky equations. The endothelial permeability and hydraulic conductivity depend on the shear stress. The numerical solution of the above equations is obtained using the finite element method. Our results confirm what the experimental studies report that LDL accumulation is achieved in artery regions where low shear stresses exist. In particular, in our model we observe elevated LDL aggregation in areas where the wall shear stress is lower than 2 Pa. Also the increase of LDL concentration occurs in a thin layer close to the artery wall at the outer parts of artery segments, which also agrees with the experimental observation. In addition, we concluded that shear stress affects the transport of macromolecules from the blood to the carotid artery wall.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2012
The aim of this study is to describe a new method for three-dimensional (3D) reconstruction of co... more The aim of this study is to describe a new method for three-dimensional (3D) reconstruction of coronary arteries using Frequency Domain Optical Coherence Tomography (FD-OCT) images. The rationale is to fuse the information about the curvature of the artery, derived from biplane angiographies, with the information regarding the lumen wall, which is produced from the FD-OCT examination. The method is based on a three step approach. In the first step the lumen borders in FD-OCT images are detected. In the second step a 3D curve is produced using the center line of the vessel from the two biplane projections. Finally in the third step the detected lumen borders are placed perpendicularly onto the path based on the centroid of each lumen border. The result is a 3D reconstructed artery produced by all the lumen borders of the FD-OCT pullback representing the 3D arterial geometry of the vessel.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011
Optical Coherence Tomography (OCT) is a fiber--optic imaging modality which produces high resolut... more Optical Coherence Tomography (OCT) is a fiber--optic imaging modality which produces high resolution tomographic images of the coronary lumen and outer vessel wall. While OCT images present morphological information in highly resolved detail, the characterization of the various plaque components relies on trained readers. The aim of this study is to extract a set of features in grayscale OCT images and to use them in order to classify the atherosclerotic plaque. Intensity and texture based features we used in order to classify the plaque in four plaque types: Calcium (C), Lipid Pool (LP), Fibrous Tissue (FT) and Mixed Plaque (MP). 50 OCT annotated images from 3 patients were used to train and test the proposed plaque characterization method. Using a Random Forests classifier overall classification accuracy 80.41% is reported.
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Papers by Lampros Michalis