Download or read book Experiments to Determine the Mechanical Properties of Arteries written by Itay Manor and published by . This book was released on 2015 with total page 103 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanical Properties of Arteries written by Jan-Lucas Gade and published by Linköping University Electronic Press. This book was released on 2019-08-29 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this Licentiate of Engineering thesis, a method is proposed that identi?es the mechanical properties of arteries in vivo. The mechanical properties of an artery are linked to the development of cardiovascular diseases. The possibility to identify the mechanical properties of an artery inside the human body could, thus, facilitate disease diagnostization, treatment and monitoring. Supplied with information obtainable in the clinic, typically limited to time- resolved pressure-radius measurement pairs, the proposed in vivo parameter identi- ?cation method calculates six representative parameters by solving a minimization problem. The artery is treated as a homogeneous, incompressible, residual stress- free, thin-walled tube consisting of an elastin dominated matrix with embedded collagen ?bers referred to as the constitutive membrane model. To validate the in vivo parameter identi?cation method, in silico arteries in the form of ?nite element models are created using published data for the human abdominal aorta. With these in silico arteries which serve as mock experiments with pre-de?ned material parameters and boundary conditions, in vivo-like pressure-radius data sets are generated. The mechanical properties of the in silico arteries are then determined using the proposed parameter identi?cation method. By comparing the identi?ed and the pre-de?ned parameters, the identi?cation method is quantitatively validated. The parameters for the radius of the stress-free state and the material constant associated with elastin show high agreement in case of healthy arteries. Larger di?erences are obtained for the material constants associated with collagen, and the largest discrepancy occurs for the in situ axial prestretch. For arteries with a pathologically small elastin content, incorrect parameters are identi?ed but the presence of a diseased artery is revealed by the parameter identi?cation method. Furthermore, the identi?ed parameters are used in the constitutive membrane model to predict the stress state of the artery in question. The stress state is thereby decomposed into an isotropic and an anisotropic component which are primarily associated with the elastin dominated matrix and the collagen ?bers, respectively. In order to assess the accuracy of the predicted stress, it is compared to the known stress state of the in silico arteries. The comparison of the predicted and the in silico decomposed stress states show a close agreement for arteries exhibiting a low transmural stress gradient. With increasing transmural stress gradient the agreement deteriorates. The proposed in vivo parameter identi?cation method is capable of identifying adequate parameters and predicting the decomposed stress state reasonably well for healthy human abdominal aortas from in vivo-like data. In diesem Lizentiat der Ingenieurwissenschaften wird eine Methode zur Identifikation der mechanischen Eigenschaften von Arterien in vivo vorgestellt. Die mechanischen Eigenschaften einer Arterie sind mit der Ausbildung kardiovaskulärer Krankheiten verknüpft und deren Identifikation hat daher das Potenzial die Diagnose, die Behandlung und die Überwachung dieser Krankheiten zu verbessern. Basierend auf klinisch möglichen Messungen, die üblicherweise auf ein zeitaufgelöstes Druck-Radiussignal limitiert sind, werden sechs repräsentative Parameter durch Lösen eines Minimierungsproblems berechnet. Die sechs Parameter sind dabei die Eingangsparameter des zur Hilfe gezogenen konstitutiven Schalenmodells welches eine Arterie als eine homogene, inkompressible, restspannungsfreie und dünnwandige Röhre beschreibt. Weiterhin wird angenommen, dass die Arterienwand aus einer elastindominierten Matrix mit eingebetteten Kollagenfasern besteht. Um die in vivo Parameteridentifikationsmethode zu validieren, werden in silico Arterien in Form von Finite Elemente Modellen erstellt. Diese in silico Arterien beruhen auf publizierten Materialparametern der menschlichen Abdominalaorta und dienen als Pseudoexperimente mit vordefinierten mechanischen Eigenschaften und Randbedingungen. Mit diesen Arterien werden in vivo-ähnliche Druck-Radiussignale erstellt und anschliesend werden ihre mechanischen Eigenschaften mit Hilfe der Parameteridentifikationsmethode bestimmt. Der Vergleich der identifizierten und der vordefinierten Parameter ermöglicht die quantitative Validierung der Methode. Die Parameter des spannungsfreien Radius und der Materialkonstanten für Elastin weisen hohe Übereinstummung im Falle gesunder Arterien auf. Die Abweichung der Materialkonstanten für Kollagen sind etwas gröser und der gröste Unterschied tritt beim axialen in situ Stretch auf. Für Arterien mit einem pathologisch geringen Elastinbestandteil werden falsche Parameter identifiziert, wobei die Parameteridentifikationsmethode eine krankhafte Arterie offenlegt. Weiterhin werden mit Hilfe der identifizierten Parameter und des konstitutiven Schalenmodells der Spannungszustand in der Arterienwand berechnet. Dieser ist dabei aufgeteilt in einen isotropen und einen anisotropen Anteil. Der isotrope Anteil wird mit der elastindomierten Matrix und der anisotrope Anteil mit den Kollagenfasern verknüpft. Um die Genauigkeit des berechneten Spannungszustandes beurteilen zu können, wird dieser mit dem Zustand in den in silico Arterien verglichen. Im Fall von Arterien, die einen geringen transmuralen Spannungsgradienten aufweisen, entspricht der berechnete Spannungszustand dem in silico Zustand. Mit zunehmendem transmuralen Spannungsgradienten lässt die Übereinstimmung nach. Für die gesunde menschliche Abdominalaorta ist die entwickelte in vivo Parameteridentifikationsmethode in der Lage, basierend auf in vivo-ähnlichen Messsignalen, adäquate Parameter zu identifizieren und einen zufriedenstellenden Spannungszustand zu berechnen. I denna licentiatavhandling föreslås en metod för att identifiera mekaniska egenskaper hos artärer in vivo. De mekaniska egenskaperna är kopplade till utvecklingen av hjärt-kärlsjukdomar, och möjligheten att identifiera dessa egenskaper skulle således kunna underlätta diagnostisering, behandling och uppföljning av dessa sjukdomar. Den förslagna metoden använder kliniskt mätbara tryck-radie-signaler och löser ett minimeringsproblem för att bestämma sex parametrar som beskriver kärlets mekaniska egenskaper. Artären modelleras som ett homogent, inkompressibelt och spänningsfritt tunnväggigt rör där kärlväggen utgörs av en elastindominerad matris armerad med inbäddade kollagenfibrer. För att validera parameteridentifieringen skapas en uppsättning representativa, virtuella artärer med hjälp av finita element. Dessa in silico-artärer baseras på publicerade data för mänsklig bukaorta och används för att generera fiktiva tryckradie-signaler vilka sedan matas in i den förslagna modellen. Genom att parametrar och randvillkor för in silico-artärerna är kända fungerar dessa som en kontroll mot vilka resultatet från parameteridentifieringen kan jämföras. Parametrarna som beskriver den icke trycksatta radien och den elastindominerade matrisen visar god överensstämmelse med de in silico-artärerna för friska kärl. Större diskrepans erhålls för de parametrar som associeras med kollagenet, och den största avvikelsen erhålls för den parameter som beskriver den axiella försträckningen. För artärer med patologiskt lågt elastininnehåll identifieras felaktiga parametrar, men resultatet avslöjar ändå tydligt en sjuk artär. De identifierade parametrarna har också använts för att jämföra spänningstillst åndet i membranmodellen och in silico-artäreren. Spänningstillståndet har delats upp i en isotrop och en anisotrop komponent svarande mot, i huvudsak, den elastindominerade matrisen samt kollagenfibrerna. Resultatet visar en mycket god överensstämmelse för bägge komponenterna hos in silico-artärer med låg spänningsgradient genom väggen. Med ökande spänningsgradient försämras dock överensstämmelsen. Resultatet visar att den förslagna metoden är kapabel att identifiera adekvata parametrar och att förutsäga spänningskomponenterna i en frisk aorta.

Download or read book Experimental Investigation of Arteries Mechanical Properties written by Ofry Efraim Yossef and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Cardiovascular diseases such as aneurisms, atherosclerosis, arterial dissection and hypertension are a leading cause for mortality in the western world. Therefore, understanding and characterization of the mechanical behavior of the arterial wall is of high importance.The mechanical response is a combined passive and active response due to the contraction of smooth muscle cells (SMCs) in the arterial wall. The passive response is attributed to the collagen fibers and elastin fibrils. For a mechanical model that describes arteries properly,both passive and active responses must be investigated. Experiments to investigate biological tissues are complex and therefore a reliable, accurate system and well defined experimental protocol are needed. Furthermore, due to the large variations between test samples, a series of experiments is required for statistically relevant data. A common assumption in the biomechanical community is that arteries are incompressible under physiological conditions. This assumption is due to the high content of water in the artery wall, which is considered incompressible. An experimental-based determination of the level of compressibility is therefore of biomechanical interest, but not easily determined because of difficulties to accurately measure very small differences in volume under a physiological pressure.Therefore, the goals of this M.Sc thesis were a) to provide an experimental-based answer to the level of compressibility of arteries, b) to expand the capabilities of an experimental system, improve its reliability and operational options, c) to perform a large number of experiments on arteries in order to create a database for the determination of material parameters. Experimental evidence on the compressibility of arteries under normal physiological pressure range is provided using a precise experimental apparatus. Nineteen experiments on porcine common carotid were performed by two students and the results were analyzed by the author with the conclusion that: in the physiological pressure range (50to 200 mmHg), a relative volume change of 0.2-5% was obtained, lower compared to the sapheneous and femoral arteries (2-6% ). Most of the arteries had a relative volume change of 0.2-1.5%. Details are given in Chapter 2 which is based on a paper published in JMBBM. An apparatus used to investigate the passive and active response of arteries was enhanced.The pressure was oscillating, unstable and not controlled, the control program was not reliable, the system had only manual operation abilities and diameter was unknown during tests. These limitations were removed. The enhanced apparatus is described in detail in Chapter 3 along with numerous experiments which prove its proper functionality. Experiments for the investigation of the passive response of human left internal mammaryartery (LIMA) (one Radial) using the improved apparatus were made which demonstrate that a typical axial in-vivo stretch ratio for human LIMA is 1.1-1.15. A series of experiments attempting to activate the smooth muscle cells (SMC's) were performed. Since the obtained human arteries provided were soaked in a vasodilator (papaverine) during surgeries, the SMC response was disabled despite "washing" them in physiological solution.Due to the inability to receive un-soaked human arteries, porcine arteries were investigated. A series of seven experiments for the investigation of the active response in porcine arteries were performed showing a maximum change of 17-27% in the diameter at 80 mmHg. The results and conclusions from those experiments and experiments on human arteries for passive response are presented in Chapter 3" -- abstract.

Download or read book Mechanical Properties of Arteries written by Jan-Lucas Gade and published by Linköping University Electronic Press. This book was released on 2021-01-27 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, a method is proposed that identifies the mechanical properties of arteries in vivo. The mechanical properties of an artery are linked to the development of cardiovascular diseases. The possibility to identify the mechanical properties of an artery inside the human body could, thus, facilitate disease diagnostization, treatment and monitoring. Supplied with information obtainable in the clinic, typically limited to time-resolved pressure-radius measurement pairs, the proposed in vivo parameter identification method solves a non-convex minimization problem to determine parameters related to the mechanical properties of the blood vessel. The artery is treated as a homogeneous, incompressible, residual stress-free, thin-walled tube consisting of an elastin dominated matrix with embedded collagen fibers. To validate the in vivo parameter identification method, in silico arteries in the form of finite element models are created using published data for the human abdominal aorta. With these in silico arteries which serve as mock experiments with pre-defined material parameters and boundary conditions, in vivo-like pressure-radius data sets are generated. The mechanical properties of the in silico arteries are then determined using the proposed parameter identification method. By comparing the identified and the pre-defined parameters, the identification method is quantitatively validated and it is shown that the parameters agree well for healthy arteries. Furthermore, the identified parameters are used to compare the stress state in the arterial model and in the in silico arteries. The stress state is thereby decomposed into an isotropic and an anisotropic component which are primarily associated with the elastin dominated matrix and the collagen fibers, respectively. The comparison of the decomposed stress states shows a close agreement for arteries exhibiting a physiological stress gradient. Another important aspect is the identification of parameters by solving a non-convex minimization problem. The non-convexity of the problem implies that incorrect parameter values, corresponding to local minima, may be found when common gradient-based solution techniques are employed. A problem-specific global algorithm based on the branch-and-bound method is, therefore, created which ensures that the global minimum and accordingly the correct parameters are obtained. It turns out that the gradient-based solution technique identifies the correct parameters if certain requirements are met, among others the use of the heuristic multi-start method. In a last step, the in vivo parameter identification method is extended to also identify parameters related to smooth muscle contraction. To prevent an overparameterization caused by the increased number of model parameters, the model is simultaneously fit to clinical data measured during three different arterial conditions: basal; constricted; and dilated. Despite the simple contraction model the extended method fits the clinical data well. Finally, in this dissertation it is shown that the proposed in vivo parameter identification method identifies the mechanical properties of arteries well. An open question for future research is how this method can be applied in a clinical setting to facilitate cardiovascular disease diagnostization, treatment and monitoring.

Download or read book Experimental Investigation of Arteries Mechanical Properties written by Ofry Efraim Yossef and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Cardiovascular diseases such as aneurisms, atherosclerosis, arterial dissection and hypertension are a leading cause for mortality in the western world. Therefore, understanding and characterization of the mechanical behavior of the arterial wall is of high importance.The mechanical response is a combined passive and active response due to the contraction of smooth muscle cells (SMCs) in the arterial wall. The passive response is attributed to the collagen fibers and elastin fibrils. For a mechanical model that describes arteries properly,both passive and active responses must be investigated. Experiments to investigate biological tissues are complex and therefore a reliable, accurate system and well defined experimental protocol are needed. Furthermore, due to the large variations between test samples, a series of experiments is required for statistically relevant data. A common assumption in the biomechanical community is that arteries are incompressible under physiological conditions. This assumption is due to the high content of water in the artery wall, which is considered incompressible. An experimental-based determination of the level of compressibility is therefore of biomechanical interest, but not easily determined because of difficulties to accurately measure very small differences in volume under a physiological pressure.Therefore, the goals of this M.Sc thesis were a) to provide an experimental-based answer to the level of compressibility of arteries, b) to expand the capabilities of an experimental system, improve its reliability and operational options, c) to perform a large number of experiments on arteries in order to create a database for the determination of material parameters. Experimental evidence on the compressibility of arteries under normal physiological pressure range is provided using a precise experimental apparatus. Nineteen experiments on porcine common carotid were performed by two students and the results were analyzed by the author with the conclusion that: in the physiological pressure range (50to 200 mmHg), a relative volume change of 0.2-5% was obtained, lower compared to the sapheneous and femoral arteries (2-6% ). Most of the arteries had a relative volume change of 0.2-1.5%. Details are given in Chapter 2 which is based on a paper published in JMBBM. An apparatus used to investigate the passive and active response of arteries was enhanced.The pressure was oscillating, unstable and not controlled, the control program was not reliable, the system had only manual operation abilities and diameter was unknown during tests. These limitations were removed. The enhanced apparatus is described in detail in Chapter 3 along with numerous experiments which prove its proper functionality. Experiments for the investigation of the passive response of human left internal mammaryartery (LIMA) (one Radial) using the improved apparatus were made which demonstrate that a typical axial in-vivo stretch ratio for human LIMA is 1.1-1.15. A series of experiments attempting to activate the smooth muscle cells (SMC's) were performed. Since the obtained human arteries provided were soaked in a vasodilator (papaverine) during surgeries, the SMC response was disabled despite "washing" them in physiological solution.Due to the inability to receive un-soaked human arteries, porcine arteries were investigated. A series of seven experiments for the investigation of the active response in porcine arteries were performed showing a maximum change of 17-27% in the diameter at 80 mmHg. The results and conclusions from those experiments and experiments on human arteries for passive response are presented in Chapter 3" -- abstract.

Download or read book A Method for Measuring the Mechanical Properties of Arterial Tissue Using Load and Displacement Sensing Indentation Experiments written by Erik Nathaniel Glaser and published by . This book was released on 2000 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Method of Determining the Mechanical Properties of Arteries in Vivo written by Frank Paul Primiano and published by . This book was released on 1963 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Biomechanics of Soft Tissue in Cardiovascular Systems written by Gerhard A. Holzapfel and published by Springer. This book was released on 2014-05-04 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book is written by leading experts in the field presenting an up-to-date view of the subject matter in a didactically sound manner. It presents a review of the current knowledge of the behaviour of soft tissues in the cardiovascular system under mechanical loads, and the importance of constitutive laws in understanding the underlying mechanics is highlighted. Cells are also described together with arteries, tendons and ligaments, heart, and other biological tissues of current research interest in biomechanics. This includes experimental, continuum mechanical and computational perspectives, with the emphasis on nonlinear behaviour, and the simulation of mechanical procedures such as balloon angioplasty.

Download or read book Equipment for Measurement of Mechanical Properties of Arteries written by Raymond Peter Vito and published by . This book was released on 1979 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nonlinear Elasticity written by Y. B. Fu and published by Cambridge University Press. This book was released on 2001-05-07 with total page 541 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive introduction to nonlinear elasticity for graduates and researchers, covering new developments in the field.

Download or read book Biomechanical Modelling at the Molecular Cellular and Tissue Levels written by Gerhard A. Holzapfel and published by Springer Science & Business Media. This book was released on 2009-06-05 with total page 351 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Regulation of Tissue Oxygenation Second Edition written by Roland N. Pittman and published by Biota Publishing. This book was released on 2016-08-18 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: This presentation describes various aspects of the regulation of tissue oxygenation, including the roles of the circulatory system, respiratory system, and blood, the carrier of oxygen within these components of the cardiorespiratory system. The respiratory system takes oxygen from the atmosphere and transports it by diffusion from the air in the alveoli to the blood flowing through the pulmonary capillaries. The cardiovascular system then moves the oxygenated blood from the heart to the microcirculation of the various organs by convection, where oxygen is released from hemoglobin in the red blood cells and moves to the parenchymal cells of each tissue by diffusion. Oxygen that has diffused into cells is then utilized in the mitochondria to produce adenosine triphosphate (ATP), the energy currency of all cells. The mitochondria are able to produce ATP until the oxygen tension or PO2 on the cell surface falls to a critical level of about 4–5 mm Hg. Thus, in order to meet the energetic needs of cells, it is important to maintain a continuous supply of oxygen to the mitochondria at or above the critical PO2 . In order to accomplish this desired outcome, the cardiorespiratory system, including the blood, must be capable of regulation to ensure survival of all tissues under a wide range of circumstances. The purpose of this presentation is to provide basic information about the operation and regulation of the cardiovascular and respiratory systems, as well as the properties of the blood and parenchymal cells, so that a fundamental understanding of the regulation of tissue oxygenation is achieved.

Download or read book 8th European Medical and Biological Engineering Conference written by Tomaz Jarm and published by Springer Nature. This book was released on 2020-11-29 with total page 1198 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book aims at informing on new trends, challenges and solutions, in the multidisciplinary field of biomedical engineering. It covers traditional biomedical engineering topics, as well as innovative applications such as artificial intelligence in health care, tissue engineering , neurotechnology and wearable devices. Further topics include mobile health and electroporation-based technologies, as well as new treatments in medicine. Gathering the proceedings of the 8th European Medical and Biological Engineering Conference (EMBEC 2020), held on November 29 - December 3, 2020, in Portorož, Slovenia, this book bridges fundamental and clinically-oriented research, emphasizing the role of education, translational research and commercialization of new ideas in biomedical engineering. It aims at inspiring and fostering communication and collaboration between engineers, physicists, biologists, physicians and other professionals dealing with cutting-edge themes in and advanced technologies serving the broad field of biomedical engineering.

Download or read book PanVascular Medicine written by Peter Lanzer and published by Springer. This book was released on 2015-03-30 with total page 5004 pages. Available in PDF, EPUB and Kindle. Book excerpt: ​Vascular management and care has become a truly multidisciplinary enterprise as the number of specialists involved in the treatment of patients with vascular diseases has steadily increased. While in the past, treatments were delivered by individual specialists, in the twenty-first century a team approach is without doubt the most effective strategy. In order to promote professional excellence in this dynamic and rapidly evolving field, a shared knowledge base and interdisciplinary standards need to be established. Pan Vascular Medicine, 2nd edition has been designed to offer such an interdisciplinary platform, providing vascular specialists with state-of-the art descriptive and procedural knowledge. Basic science, diagnostics, and therapy are all comprehensively covered. In a series of succinct, clearly written chapters, renowned specialists introduce and comment on the current international guidelines and present up-to-date reviews of all aspects of vascular care.

Download or read book An Experimental Method for Measuring written by and published by DIANE Publishing. This book was released on with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Biomechanical Systems written by Cornelius T. Leondes and published by CRC Press. This book was released on 2000-12-26 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: Because of developments in powerful computer technology, computational techniques, advances in a wide spectrum of diverse technologies, and other advances coupled with cross disciplinary pursuits between technology and its greatly significant applied implications in human body processes, the field of biomechanics is evolving as a broadly significant area. The four volumes of Biomechanical Systems, Techniques, and Applications explore the many areas of significant advances, including dynamics of musculo-skeletal systems; mechanics of hard and soft tissues, muscles, bone remodeling, hard and soft tissue interfaces, blood flow, air flow, flow-prosthesis interfaces, and impact; cardiovascular and respiratory biomechanics; and dynamics of many machine interactions.

Download or read book Biomechanics written by Y. C. Fung and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 443 pages. Available in PDF, EPUB and Kindle. Book excerpt: The motivation for writing aseries ofbooks on biomechanics is to bring this rapidly developing subject to students of bioengineering, physiology, and mechanics. In the last decade biomechanics has become a recognized disci pline offered in virtually all universities. Yet there is no adequate textbook for instruction; neither is there a treatise with sufficiently broad coverage. A few books bearing the title of biomechanics are too elementary, others are too specialized. I have long feIt a need for a set of books that will inform students of the physiological and medical applications of biomechanics, and at the same time develop their training in mechanics. We cannot assume that all students come to biomechanics already fully trained in fluid and solid mechanics; their knowledge in these subjects has to be developed as the course proceeds. The scheme adopted in the present series is as follows. First, some basic training in mechanics, to a level about equivalent to the first seven chapters of the author's A First Course in Continuum Mechanics (Prentice-Hall,lnc. 1977), is assumed. We then present some essential parts of biomechanics from the point of view of bioengineering, physiology, and medical applications. In the meantime, mechanics is developed through a sequence of problems and examples. The main text reads like physiology, while the exercises are planned like a mechanics textbook. The instructor may fil1 a dual role: teaching an essential branch of life science, and gradually developing the student's knowledge in mechanics.