Relation between plaque type, plaque thickness, blood shear stress, and plaque stress in coronary arteries assessed by X-ray Angiography and Intravascular Ultrasound

Purpose: Atheromatic plaque progression is affected, among others phenomena, by biomechanical, biochemical, and physiological factors. In this paper, the authors introduce a novel framework able to provide both morphological (vessel radius, plaque thickness, and type) and biomechanical (wall shear stress and Von Mises stress) indices of coronary arteries. Methods: First, the approach reconstructs the three-dimensional morphology of the vessel from intravascular ultrasound(IVUS) and Angiographic sequences, requiring minimal user interaction. Then, a computational pipeline allows to automatically assess fluid-dynamic and mechanical indices. Ten coronary arteries are analyzed illustrating the capabilities of the tool and confirming previous technical and clinical observations. Results: The relations between the arterial indices obtained by IVUS measurement and simulations have been quantitatively analyzed along the whole surface of the artery, extending the analysis of the coronary arteries shown in previous state of the art studies. Additionally, for the first time in the literature, the framework allows the computation of the membrane stresses using a simplified mechanical model of the arterial wall. Conclusions: Circumferentially (within a given frame), statistical analysis shows an inverse relation between the wall shear stress and the plaque thickness. At the global level (comparing a frame within the entire vessel), it is observed that heavy plaque accumulations are in general calcified and are located in the areas of the vessel having high wall shear stress. Finally, in their experiments the inverse proportionality between fluid and structural stresses is observed

IVUS – UBPCL(I)

Treballs Finals de Grau d'Enginyeria Informàtica, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2013, Director: Petia RadevaEn los últimos años la medicina ha avanzado a una velocidad vertiginosa, en parte por nuevos descubrimientos y en parte causado por la evolución tecnológica. Esto hace que se presenten nuevos problemas, ya que ahora somos capaces de extraer gran cantidad de información, pero nos encontramos delante de un gran muro que hay que sortear. Este muro es la dificultad de tratar y obtener resultados de este volumen ingente de información. En nuestro caso, la tecnología IVUS ha supuesto un gran avance para la detección y el tratamiento de enfermedades de las arterias coronarias (EAC), pero también ha supuesto un reto cómo obtener la información, ya que, gracias a la tecnología IVUS tenemos que lidiar con una gran cantidad de imágenes. El objetivo de nuestro proyecto es crear una herramienta que ayude al profesional a tratar y procesar toda la información de la manera más cómoda y rápida posible para poder obtener el mejor resultado y diagnosticar o tratar al paciente

Intravascular Ultrasound

Intravascular ultrasound (IVUS) is a cardiovascular imaging technology using a specially designed catheter with a miniaturized ultrasound probe for the assessment of vascular anatomy with detailed visualization of arterial layers. Over the past two decades, this technology has developed into an indispensable tool for research and clinical practice in cardiovascular medicine, offering the opportunity to gather diagnostic information about the process of atherosclerosis in vivo, and to directly observe the effects of various interventions on the plaque and arterial wall. This book aims to give a comprehensive overview of this rapidly evolving technique from basic principles and instrumentation to research and clinical applications with future perspectives

2D and 3D segmentation of medical images.

"Cardiovascular disease is one of the leading causes of the morbidity and mortality in the western world today. Many different imaging modalities are in place today to diagnose and investigate cardiovascular diseases. Each of these, however, has strengths and weaknesses. There are different forms of noise and artifacts in each image modality that combine to make the field of medical image analysis both important and challenging. The aim of this thesis is develop a reliable method for segmentation of vessel structures in medical imaging, combining the expert knowledge of the user in such a way as to maintain efficiency whilst overcoming the inherent noise and artifacts present in the images. We present results from 2D segmentation techniques using different methodologies, before developing 3D techniques for segmenting vessel shape from a series of images. The main drive of the work involves the investigation of medical images obtained using catheter based techniques, namely Intra Vascular Ultrasound (IVUS) and Optical Coherence Tomography (OCT). We will present a robust segmentation paradigm, combining both edge and region information to segment the media-adventitia, and lumenal borders in those modalities respectively. By using a semi-interactive method that utilizes "soft" constraints, allowing imprecise user input which provides a balance between using the user's expert knowledge and efficiency. In the later part of the work, we develop automatic methods for segmenting the walls of lymph vessels. These methods are employed on sequential images in order to obtain data to reconstruct the vessel walls in the region of the lymph valves. We investigated methods to segment the vessel walls both individually and simultaneously, and compared the results both quantitatively and qualitatively in order obtain the most appropriate for the 3D reconstruction of the vessel wall. Lastly, we adapt the semi-interactive method used on vessels earlier into 3D to help segment out the lymph valve. This involved the user interactive method to provide guidance to help segment the boundary of the lymph vessel, then we apply a minimal surface segmentation methodology to provide segmentation of the valve.

TOWARDS HIGH RESOLUTION ENDOSCOPIC OPTICAL COHERENCE TOMOGRAPHY FOR IMAGING INTERNAL ORGANS

Optical coherence tomography (OCT) is a light based interferometric imaging technique that can provide high resolution (5-20 µm at 1300 nm), depth resolved, images in real-time. With recent advances in portable low coherent light sources for OCT it is now possible to achieve ultrahigh axial resolutions (≤ 3 µm) by moving to shorter central wavelengths such as 800 nm while utilizing a broad spectral bandwidth. Our goal was to push ultrahigh resolution OCT technology to in vivo imaging of internal organs for endoscopic assessment of tissue microstructure. This dissertation is separated into technological developments and biomedical imaging studies. Technological developments in this dissertation included development of a high speed, ultrahigh resolution distal scanning catheter. This catheter was based upon a miniature DC micromotor capable of rotational velocities in excess of 100 rps, a diffractive compound lens design that minimized chromatic aberrations, and a mechanical assembly that limited field of view blockage to less than 7.5% and maintained an outer diameter of 1.78 mm (with plastic sheath). In conjunction with the algorithm described in chapter 4 to correct for non-uniform rotational distortion, the overall imaging system was capable of high quality endoscopic imaging of internal organs in vivo. Equipped with the ultrahigh resolution endoscopic OCT system, imaging was performed in small airways and colorectal cancer. Imaging results demonstrated the ability to directly visualization of microstructural details such as airway smooth muscle in the small airways representing a major step forward in pulmonary imaging. With the ability to visualize airway smooth muscle, morphological changes in COPD and related diseases can be further investigated. Additionally, longitudinal changes in an ETBF induced colon cancer model in APCMin mice were studied as well. Quantitative assessment of tissue microarchitecture was performed by measuring the attenuation coefficient to find a bimodal distribution separating normal healthy tissue from polyps. Finally, results from two additional projects were also demonstrated. Chapter 7 shows some results from vascular imaging in a tumor angiogenesis model and middle cerebral artery occlusion model. Chapter 8 describes an endoscopic multimodal OCT and fluorescence imaging platform with results in ex vivo rabbit esophagus