1. Articles from Lampros K. Michalis

    1-15 of 15
    1. Optical coherence tomography in coronary atherosclerosis assessment and intervention

      Optical coherence tomography in coronary atherosclerosis assessment and intervention

      Since optical coherence tomography (OCT) was first performed in humans two decades ago, this imaging modality has been widely adopted in research on coronary atherosclerosis and adopted clinically for the optimization of percutaneous coronary intervention. In the past 10 years, substantial advances have been made in the understanding of in vivo vascular biology using OCT. Identification by OCT of culprit plaque pathology could potentially lead to a major shift in the management of patients with acute coronary syndromes. Detection by OCT of healed coronary plaque has been important in our understanding of the mechanisms involved in plaque destabilization and healing ...

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    2. Utility of Multimodality Intravascular Imaging and the Local Hemodynamic Forces to Predict Atherosclerotic Disease Progression

      Utility of Multimodality Intravascular Imaging and the Local Hemodynamic Forces to Predict Atherosclerotic Disease Progression

      Objectives This study sought to examine the utility of multimodality intravascular imaging and of the endothelial shear stress (ESS) distribution to predict atherosclerotic evolution. Background There is robust evidence that intravascular ultrasound (IVUS)-derived plaque characteristics and ESS distribution can predict, with however limited accuracy, atherosclerotic evolution; nevertheless, it is yet unclear whether multimodality imaging and ESS mapping enable more accurate prediction of coronary plaque progression. Methods A total of 44 patients admitted with a myocardial infarction that had successful revascularization and 3-vessel IVUS and optical coherence tomography (OCT) imaging at baseline and 13-month follow-up were included in the study ...

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    3. Error propagation in the characterization of atheromatic plaque types based on imaging

      Error propagation in the characterization of atheromatic plaque types based on imaging

      Imaging systems transmit and acquire signals and are subject to errors including: error sources, signal variations or possible calibration errors. These errors are included in all imaging systems for atherosclerosis and are propagated to methodologies implemented for the segmentation and characterization of atherosclerotic plaque. In this paper, we present a study for the propagation of imaging errors and image segmentation errors in plaque characterization methods applied to 2D vascular images. More specifically, the maximum error that can be propagated to the plaque characterization results is estimated, assuming worst-case scenarios. The proposed error propagation methodology is validated using methods applied to ...

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    4. Endothelial Shear Stress and Coronary Plaque Characteristics in Humans: A Combined Frequency-Domain Optical Coherence Tomography and Computational Fluid Dynamics Study

      Endothelial Shear Stress and Coronary Plaque Characteristics in Humans: A Combined Frequency-Domain Optical Coherence Tomography and Computational Fluid Dynamics Study

      Background —Despite the exposure of the entire vasculature to the atherogenic effects of systemic risk factors, atherosclerotic plaques preferentially develop at sites with disturbed flow. This study aimed at exploring in vivo the relationship between local endothelial shear stress (ESS) and coronary plaque characteristics in humans, using computational fluid dynamics and frequency-domain optical coherence tomography (FD-OCT). Methods and Results —Three-dimensional coronary artery reconstruction was performed in 21 patients (24 arteries) presenting with acute coronary syndrome using FD-OCT and coronary angiography. Each coronary artery was divided into sequential 3-mm segments, and analyzed for the assessment of local ESS and plaque characteristics ...

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    5. Currently available methodologies for the processing of intravascular ultrasound and optical coherence tomography images

      Currently available methodologies for the processing of intravascular ultrasound and optical coherence tomography images

      Optical coherence tomography and intravascular ultrasound are the most widely used methodologies in clinical practice as they provide high resolution cross-sectional images that allow comprehensive visualization of the lumen and plaque morphology. Several methods have been developed in recent years to process the output of these imaging modalities, which allow fast, reliable and reproducible detection of the luminal borders and characterization of plaque composition. These methods have proven useful in the study of the atherosclerotic process as they have facilitated analysis of a vast amount of data. This review presents currently available intravascular ultrasound and optical coherence tomography processing methodologies ...

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    6. Effect of the Endothelial Shear Stress Patterns on Neointimal Proliferation Following Drug-Eluting Bioresorbable Vascular Scaffold Implantation : An Optical Coherence Tomography Study

      Effect of the Endothelial Shear Stress Patterns on Neointimal Proliferation Following Drug-Eluting Bioresorbable Vascular Scaffold Implantation : An Optical Coherence Tomography Study

      Objectives The goal of this study was to investigate the effect of endothelial shear stress (ESS) on neointimal formation following an Absorb bioresorbable vascular scaffold (BVS) (Abbott Vascular, Santa Clara, California) implantation. Background Cumulative evidence, derived from intravascular ultrasound–based studies, has demonstrated a strong association between local ESS patterns and neointimal formation in bare-metal stents, whereas in drug-eluting stents, there are contradictory data about the effect of ESS on the vessel wall healing process. The effect of ESS on neointimal development following a bioresorbable scaffold implantation remains unclear. Methods Twelve patients with an obstructive lesion in a relatively straight ...

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    7. Methodology for fully automated segmentation and plaque characterization in intracoronary optical coherence tomography images

      Methodology for fully automated segmentation and plaque characterization in intracoronary optical coherence tomography images

      Optical coherence tomography (OCT) is a light-based intracoronary imaging modality that provides high-resolution cross-sectional images of the luminal and plaque morphology. Currently, the segmentation of OCT images and identification of the composition of plaque are mainly performed manually by expert observers. However, this process is laborious and time consuming and its accuracy relies on the expertise of the observer. To address these limitations, we present a methodology that is able to process the OCT data in a fully automated fashion. The proposed methodology is able to detect the lumen borders in the OCT frames, identify the plaque region, and detect ...

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    8. Fusion of optical coherence tomographic and angiographic data for more accurate evaluation of the endothelial shear stress patterns and neointimal distribution after bioresorbable scaffold implantation: comparison with intravascular ultrasound-derived rec

      Fusion of optical coherence tomographic and angiographic data for more accurate evaluation of the endothelial shear stress patterns and neointimal distribution after bioresorbable scaffold implantation: comparison with intravascular ultrasound-derived rec

      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 ...

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    9. Fully automated calcium detection using optical coherence tomography

      Fully automated calcium detection using optical coherence tomography

      Optical Coherence Tomography (OCT) is a new invasive technology for performing high-resolution cross-sectional 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 ...

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    10. New Developments in Hybrid Optical Coherence Tomographic Imaging: Current Status and Potential Implications in Clinical Practice and Research

      New Developments in Hybrid Optical Coherence Tomographic Imaging: Current Status and Potential Implications in Clinical Practice and Research

      Optical coherence tomography (OCT) is a relatively new imaging technique that was introduced to overcome limitations of previous imaging modalities. OCT provides high resolution cross-sectional images of the coronaries which permit detailed evaluation of the luminal morphology and assessment of coronary artery pathology. These unique qualities render OCT a useful tool in clinical practice and research arena. However, apart from its significant advantages OCT imaging has also considerable limitations. To overcome the pitfalls of OCT, fusion of this modality with other imaging techniques has been proposed. Today several hybrid catheter and sophisticated data fusion methodologies have been developed for this ...

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    11. In vivo assessment of the three-dimensional haemodynamic micro-environment following drug-eluting bioresorbable vascular scaffold implantation in a human coronary artery: fusion of frequency domain optical coherence tomography and angiography

      In vivo assessment of the three-dimensional haemodynamic micro-environment following drug-eluting bioresorbable vascular scaffold implantation in a human coronary artery: fusion of frequency domain optical coherence tomography and angiography

      The biplane angiographic data, acquired after implantation of an everolimus-eluting bioresorbable vascular scaffold (Absorb™ BVS; Abbott Vascular, Santa Clara, CA, USA) in the right coronary artery of a 46-year-old patient, were separately fused with frequency domain optical coherence tomography (FD-OCT) and intravascular ultrasound (IVUS) data to reconstruct the three-dimensional (3-D) anatomy. The local shear stress (SS) distribution in the FD-OCT- and IVUS-based models was assessed using computational fluid dynamics. The FD-OCT-based reconstruction (Figure 1A) allowed imaging of the lumen irregularities in the scaffolded segment due to strut protrusion (Figure 1B), which caused recirculation zones around the struts (Figure 1C). In ...

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    12. Fusion of optical coherence tomography and coronary angiography — In vivo assessment of shear stress in plaque rupture

      Fusion of optical coherence tomography and coronary angiography — In vivo assessment of shear stress in plaque rupture

      Advancements in cardiovascular imaging [e.g. computed tomographic coronary angiography (CTCA)] and new developments in image processing [e.g. fusion of intravascular ultrasound (IVUS) with angiographic data, fusion of IVUS with CTCA] permitted complete and comprehensive three dimensional (3D) reconstruction of coronary arteries and allowed us to study in-vivo the role of blood flow dynamics in the atherosclerotic process. Over the last years several studies used 3D reconstruction techniques to demonstrate that local hemodynamics are involved in the atherosclerotic evolution and affect the composition of the plaque . However, indigenous limitations of the implemented imaging techniques (mainly the increased noise and ...

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    13. Focus on the research utility of intravascular ultrasound - comparison with other invasive modalities

      Focus on the research utility of intravascular ultrasound - comparison with other invasive modalities

      Intravascular ultrasound (IVUS) is an invasive modality which provides cross-sectional images of a coronary artery. In these images both the lumen and outer vessel wall can be identified and accurate estimations of their dimensions and of the plaque burden can be obtained. In addition, further processing of the IVUS backscatter signal helps in the characterization of the type of the plaque and thus it has been used to study the natural history of the atherosclerotic evolution. On the other hand its indigenous limitations do not allow IVUS to assess accurately stent struts coverage, existence of thrombus or exact site of ...

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    1-15 of 15
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    Focus on the research utility of intravascular ultrasound - comparison with other invasive modalities Fusion of optical coherence tomography and coronary angiography — In vivo assessment of shear stress in plaque rupture In vivo assessment of the three-dimensional haemodynamic micro-environment following drug-eluting bioresorbable vascular scaffold implantation in a human coronary artery: fusion of frequency domain optical coherence tomography and angiography New Developments in Hybrid Optical Coherence Tomographic Imaging: Current Status and Potential Implications in Clinical Practice and Research Fully automated calcium detection using optical coherence tomography Fusion of optical coherence tomographic and angiographic data for more accurate evaluation of the endothelial shear stress patterns and neointimal distribution after bioresorbable scaffold implantation: comparison with intravascular ultrasound-derived rec Methodology for fully automated segmentation and plaque characterization in intracoronary optical coherence tomography images Effect of the Endothelial Shear Stress Patterns on Neointimal Proliferation Following Drug-Eluting Bioresorbable Vascular Scaffold Implantation : An Optical Coherence Tomography Study Currently available methodologies for the processing of intravascular ultrasound and optical coherence tomography images Endothelial Shear Stress and Coronary Plaque Characteristics in Humans: A Combined Frequency-Domain Optical Coherence Tomography and Computational Fluid Dynamics Study A Deep Learning Framework for the Detection and Quantification of Reticular Pseudodrusen and Drusen on Optical Coherence Tomography Quantitative assessment of textural features in the early detection of diabetic retinopathy with optical coherence tomography angiography