Dissertations / Theses on the topic 'Skin biomechanics'
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Ebersole, Gregory C. "Engineered Skin Biomechanics and the Deformation Behavior of Tissue Engineering Scaffolds." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306765479.
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Monat, Heath Barnhart. "Lumbar Skin Profile Prediction from Anterior and Lateral Torso Measurements." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343062090.
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Lynch, Barbara. "Multiscale biomechanics of skin: experimental investigation of the role of the collagen microstructure." Palaiseau, Ecole polytechnique, 2015. https://theses.hal.science/tel-01237007/document.
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Skin is a complex organ consisting of three main layers, namely the epidermis, dermis and hypodermis. The dermis is responsible for most of the complex mechanical properties of skin, including non-linearity, anisotropy and viscoelasticity. Like all soft collagenous tissues, the dermis is constituted mostly of extracellular matrix proteins, fibrillar collagens being the major structural components. Modelling efforts using a scaling-up approach for skin generally lack appropriate micro-mechanical experiments to clarify the link between macroscopic mechanical properties and microstructural behaviour. The goal of this research was to measure the evolution of skin's microstructure during mechanical stimulation to identify the relevant mechanisms at the microscopic scale. Uniaxial tensile tests were carried out on ex vivo mice skin under a multiphoton microscope with Second Harmonic Generation detection. This technique allows for specific imaging of collagen fibres in the depth of the dermis. We were then able to simultaneously monitor the tissue's mechanical response and image the microstructural reorganisation of the fibrillar collagen network, using quantitative characterisations at both scales. We showed that the collagen fibres continuously align in the direction of traction with stretch, generating the observed mechanical response. A general framework of hypothetical microstructural mechanisms was proposed to account for the features observed experimentally. Genetic mutations inducing a decreased or abnormal collagen synthesis can result in defective mechanical properties in skin. For instance, patients suffering from Ehlers-Danlos syndrome, a general collagenous tissue disorder caused by mutations in the genes coding for a minor form of collagen, typically present hyperelastic skin. We applied our multiscale approach to two genetically-modified mice strains created in the context of investigating the Ehlers-Danlos syndrome. The ageing process is also a factor of change in skin's mechanical properties, and was investigated in this work through experiments on aged mice skin. Genetically-modified and aged mice skin exhibited altered collagen reorganisation and mechanical response during a tensile test. The variations were interpreted in the context of the microstructural interpretation developed for control mice, and can be used for phenotyping. These findings show that our multiscale approach provides new crucial information on the biomechanics of skin. It can be generalised to study other pathologies, other collagenous tissues, or other mechanical properties, such as the biaxial or viscoelastic response.
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Newman, Steven J. "Crawling without Wiggling: Muscular Mechanisms and Kinematics of Rectilinear Locomotion in Boa Constrictors." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin150512929603962.
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Blackstone, Britani Nicole. "Biomaterial, Mechanical and Molecular Strategies to Control Skin Mechanics." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406123409.
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Schroeck, Christopher A. "A Reticulation of Skin-Applied Strain Sensors for Motion Capture." Cleveland State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=csu1560294990047589.
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Kahn, Julie. "Biomechanics of Patient Handling Slings Associated with Spinal Cord Injuries." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4702.
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Pressure ulcers and related skin integrity threats are a significant problem in current transfer/transport systems used for spinal cord injury patients. To understand this problem twenty-three different slings with varying type, material, and features were analyzed in hopes to identify at-risk areas for skin integrity threats such as pressure ulcers. Population samples included non-disabled (otherwise referred to as "healthy") volunteers as well as SCI patients from the James A. Haley Veterans Hospital. High resolution pressure interface mapping was utilized to directly measure the interface pressures between the patient and sling interface. Overall results provide relevant feedback on the systems used and to suggest a particular type of sling that might reduce and possibly minimize skin integrity threats as well as extend safe patient handling guidelines with sling use. It was found that the highest interface pressures convened along the seams of the sling, regardless of manufacturer or type.
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Balois, Thibaut. "Modélisation de croissance de tumeurs : cas particulier des mélanomes." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE033/document.
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Le mélanome est un cancer dont la mortalité augmente rapidement avec le temps. Afin d'assurer une détection précoce, des campagnes de sensibilisation ont été menées donnant des critères morphologiques pour le distinguer des grains de beauté. Mais, l'origine des différences d'aspects entre lésions bénignes et malignes reste inconnue. L'objectif est ici de relier les effets des modifications génétiques à l'aspect des tumeurs, en utilisant des outils venus de la physique macroscopique. Les mélanomes ont l'avantage d'être facilement observables et fins, ce qui en font un système idéal. Ce travail commence par rappeler les aspects physiologiques des cancers de la peau. On explique le fonctionnement de la peau saine, puis nous décrivons les différents types de lésions cutanées, et enfin nous donnons un bref aperçu des différents chemins génétiques connus menant au mélanome. Ensuite, nous faisons un rappel des différents modèles mathématiques du cancer. Nous nous attardons sur l'utilisation de la théorie des mélanges comme base théorique de mise en équation des tumeurs. Nous l'appliquons ensuite dans un modèle simplifié à deux phases en deux dimensions. Puis, nous analysons ces équations. Une étude des composantes spatiales montre la possibilité d'un processus de séparation de phases : la décomposition spinodale. L'étude temporelle permet de montrer que ces équations contiennent les ingrédients nécessaires à décrire plusieurs types de mélanomes observés in vivo. Nous terminons par l'étude des effets de la troisième dimension jusqu'alors mis de côté dans le modèle. Nous mettons en équation des mélanomes évoluant sur un épiderme ondulé, au niveau des mains et des piedsMelanoma is a cancer whose mortality grows rapidly with time. In order to insure an early diagnosis, advertising campaigns have emphasized the importance of morphological criteria in order to distinguish moles from melanoma. But, the origins of those criteria are still poorly understood. Our goal is to understand the link between genetic modifications and melanoma patterns using physical tools. As melanoma is easily observable and thin, this makes it an ideal system. This work begins by recalling the physiological aspect of skin cancer. Healthy skin is thoroughly described, then cancerous lesions are depictesd, and melanoma genetic pathways are briefly discussed. Then, continuous mathematical models of cancer are reviewed. We show how mixture theory is used to put cancer into equations. Then, this framework is simplified in a two phases 2D model.Those equations are analysed. The spatial study shows the possibility of a phase separation process: the spinodal decomposition. And, the time study shows thet this model contains the ingredients necessary to describe several melanoma types seen in vivo.Focussing finally on the third dimension. Melanoma evolving on a wavy epidermis (hands and feet skin) are studied. We explain how melanoma patterns should follow the skin ridges (fingerprints)
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Li, Duo. "Biomechanical simulation of the hand musculoskeletal system and skin." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44027.
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Pond, Damien. "Constitutive modelling of the skin accounting for chronological ageing." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25376.
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The skin is the largest organ in the human body. It is the first line of contact with the outside world, being subject to a harsh array of physical loads and environmental factors. In addition to this, the skin performs numerous physiological tasks such as thermo-regualtion, vitamin D synthesis and neurotransduction. The skin, as with all biological tissue, is subject to chronological ageing, whereby there is a general breakdown of tissue function and a decline in mechanical properties. In addition to this, skin undergoes extrinsic forms of ageing through exposure to external factors such as ultraviolet radiation, air pollution and cigarette smoking. Skin modelling is an area of biomechanics that, although medical in nature, has expanded into areas such as cosmetics, military, sports equipment and computer graphics. Skin can be approximated at the macroscopic continuum scale as an anisotropic, nearly-incompressible, viscoelastic and non-linear material whose material properties are highly dependent on the ageing process. Through the literature, several phenomenologically based models have been satisfactorily employed to capture the behaviour inherent to the skin, but despite the intrinsic link to age, to date no constitutive model for the UV-induced ageing/damage of skin has been developed that is both capable of capturing the material and structural effects, and is embedded in the rigorous framework of non-linear continuum mechanics. Such a mechanistic model is proposed here. The macroscopic response of the skin is due to microscopic components such as collagen, elastin and the surrounding ground substance and the interaction between them. An overview on the structure of the skin helps motivate the form of the continuum model and identifies which aspects of the skin need to be captured in order to replicate the macroscopic response. Furthermore, the ageing process is explored and a firm understanding of the influence of ageing on the substructures is established. Over time, elastin levels tend to decrease which results in a loss of skin elasticity. Collagen levels drop with age, but tend to flatten out which results in an overall increase in skin stiffness and loss of anisotropy. A worm-like chain constitutive model, arranged in an 8-chain configuration, is employed to capture the mechanical response of the skin. The use of such a micro-structurally-motivated model attempts to connect the underlying substructures (collagen, elastin and ground substance) present in the skin to the overall mechanical response. The constitutive model is implemented within a finite element scheme. Simple uniaxial tests are employed to ascertain the validity of the model, whereby skin samples are stretched to elicit the typical anisotropic locking response. A more complex loading condition is applied through bulge tests where a pressure is applied to an in vitro skin specimen. This more complex test is subsequently used to conduct a series of ageing numerical experiments to ascertain the response of the model to changes in material properties associated with ageing. A modified model is then proposed to capture the ageing response of the skin. The key microscopic biophysical processes that underpin ageing are identified, approximated and adapted sufficiently to be of use in the macroscopic continuum model. Aspects of open-system thermodynamics and mixture theory are adapted to the context of ageing in order to capture a continuous ageing response.
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Choi, Jiwon 1977. "The role of fibulin-5 : in the ultrastructural and biomechanical properties of skin." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81611.
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Properly assembled elastic fibers play an important role in providing skin with the properties of elasticity and resilience to allow for considerable mobility, but the mechanisms involved in elastic fiber assembly remains unknown. Fibulin-5 is an extracellular 66kDa glycoprotein synthesized and secreted by fibroblasts in skin, and has the ability to bind to tropoelastin. This study addresses (1) the role of fibulin-5 in the ultrastructure of elastic fibers in skin, and (2) its function in the cutaneous mechanical properties by using wild type and fibulin-5 null mice. In the first part, skin of fibulin-5 null mice as well as wild type mice was investigated in order to gain insight into the function of fibulin-5 in elastic fiber assembly. Using light and electron microscopy, the dramatic defects of dermal elastic fibers in the absence of fibulin-5 were analyzed. Interestingly, in the immunoelectron microscopy for LOXL-1, an enzyme responsible for the elastin cross-links, fibulin-5 null mouse skin exhibited similar immunoreactivity for LOXL-1 to wild type skin. Moreover, in the wild type skin, fibulin-5 localized to the microfibril-elastin interface at the edges and within the elastic fiber. In the second part of this study, the function of fibulin-5 in skin biomechanics was studied in order to determine its role in skin strength and elasticity. By using tensile tests, fibulin-5 null mouse skin was found to be significantly stiffer and weaker than wild type skin. Taken together, the defective elastic fibers in the absence of fibulin-5 suggest that fibulin-5 is involved in a secondary step of cutaneous elastic fiber assembly and in the mechanical properties of adult mouse skin.
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GALAL, TAREK. "Interactions ondes electromagnetiques et surfaces rugueuses : applications a la surface cutanee." Besançon, 1989. http://www.theses.fr/1989BESA2007.
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Solution analytique de la dispersion d'une onde electromagnetique par une surface rugueuse, prenant en compte les parametres locaux de la topographie=une autre technique est developpee basee sur l'utilisation d'elements finis ou de differences finies
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Yoshida, Hiroaki. "BIOMECHANICAL ANALYSES ON NONLINEAR BEHAVEIORS OF THE HUMAN SOFT TISSUES IN DYNAMIC NECK MOTION UNDER IMPACT LOADING AND TOPOLOGICAL SKIN PROPERTIES UNDER SUTURING DEFORMATION." Kyoto University, 2001. http://hdl.handle.net/2433/150663.
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Baker, Mark Ralph. "Late radiation effects in radiotherapy : changes in the biomechanical properties of normal skin, and surgically produced lesions after X irradiation measured in vivo and in vitro." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335860.
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Thomas, Mark. "A physiological and biomechanical profile of the athletes competing in a World Cup cross-country ski relay event." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0024/MQ33458.pdf.
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Bailly, Nicolas. "Traumatologie et systèmes de protection de la tête dans la pratique des sports de glisse alpins." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4102.
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Ce travail de recherche porte sur la compréhension du traumatisme crânien (TC) dans les sports de glisse alpins dans l’objectif d’améliorer et d’encadrer la conception et l’évaluation des casques de ski. Il s’est décomposé en quatre étapes :Etudier les accidents de ski conduisant au TC en identifiant des typologies d’accidents de ski et de snowboard conduisant fréquemment à l’apparition de TC. A partir d’un questionnaire rempli dans 10 cabinets médicaux et 3 hôpitaux, dix scénarios d’accident ont été identifiés ainsi que les zones de la tête les plus impactées. Cette analyse est complétée par des mesures de vitesse des skieurs.Identifier les conditions d’impact de la tête en reproduisant numériquement la cinématique de ces accidents avec un modèle multicorps de skieur. Deux types d’impact ressortent de cette analyse: les impacts sur neige, majoritaires (70%) et plutôt de faibles gravités et les impacts lors de collisions, plus rares, mais souvent plus graves.Évaluer la capacité des casques à réduire le TC en combinant approches expérimentales (impact de tête instrumentée sur neige) et simulations par éléments finis (reproduction d’impacts réalistes avec un modèle d’humain virtuel). Le casque réduit efficacement le risque de TC grave lors d’impact contre un obstacle rigide, mais son efficacité reste limitée lors d’impacts contre de la neige.Explorer des pistes d’amélioration du casque. Trois solutions ont été proposées, évaluées expérimentalement et numériquement et optimisées au regard des deux impacts cibles « neige » et « obstacle ». Le prototype proposé réduit de 30% les niveaux d’accélération de la tête lors de ces impacts par rapport aux casques traditionnelsThe aim of the project was to better understand traumatic brain injury (TBI) in alpine sports in order to improve the design and the evaluation of helmets. The work was divided in four main steps: Study skiing and snowboarding accidents leading to TBI: Ten scenarios were identified with a survey available in 10 medical centers and in 3 hospitals. The frontal and occipital zones were the most impacted parts of the head. Speed measurements were performed on ski slopes to complete the accident conditions analysis.Identify head impact conditions during these accidents: We reproduced the kinematics of these accidents using a numerical model of skier and snowboarder (multibody model). We identified two types of impact: impacts against the snow are the most frequent (70%) and are associated with mild TBI whereas impacts during collision are less frequent but are more likely to induce severe TBI. Evaluate helmet effectiveness in reducing the TBI combining experimental approach (Impacts of an instrumented head against the snow) and finite element simulations (Realistic head impacts reproduced numerically using a human model). Helmets were good at reducing the risk of severe TBI during an impact against a rigid obstacle. However the effectiveness of the helmets at reducing injury risk during an impact against the snow was limited. Improve helmet design: Three solutions were studied. These solutions were proposed, evaluated experimentally and numerically and optimized regarding the two targeted impacts “snow” and “obstacle”. The prototype of the optimized helmet reduces by 30% the acceleration of the head during these impacts compared to traditional helmets
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Bessone, Veronica [Verfasser], Ansgar [Akademischer Betreuer] Schwirtz, Hermann [Gutachter] Schwameder, and Ansgar [Gutachter] Schwirtz. "Biomechanical Analysis of Ski Jumping Landing by means of Wearable Sensors / Veronica Bessone ; Gutachter: Hermann Schwameder, Ansgar Schwirtz ; Betreuer: Ansgar Schwirtz." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1203299923/34.
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Zahrebelna, A. O. "Smart biomask." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/45339.
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Arlington, people who suffered burns of the face could have their facial skin regrown by wearing intelligent biomechanical masks. Scientists at UT Arlington in cooperation with the US Army and Northwestern University have a great aim. This invention is going to help suffered people to live comfortably in the modern world. Under conventional treatment, damaged tissue is removed and then special grafts are replaced on the burned place of the skin. But there are some flaws of such a procedure – it can often cause speech problems, scarring and other skin deformities. Besides, all the accompanying problems may require multiple operations.
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Dakpé, Stéphanie. "Etude biomécanique de la mimique faciale." Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2203/document.
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Ce travail de thèse, inclus dans un projet structurant plus vaste, projet SIMOVI (SImulation des MOuvements du VIsage), s’attache à étudier spécifiquement la mimique faciale en corrélant les déplacements visibles du revêtement cutané et les mouvements musculaires internes à travers le développement de plusieurs méthodologies. L’ensemble de la mimique faciale ne pouvant être étudié, étant donné la multitude d’expressions, les mouvements pertinents à étudier dans nos travaux ont été identifiés. Ces mouvements ont été caractérisés chez 23 sujets jeunes dans une analyse descriptive qualitative et clinique, basée sur une méthodologie s’appuyant sur l’analyse d’enregistrements vidéoscopiques, et le développement d’un codage issu du FACS (Facial Action Coding System). Une cohorte de référence a ainsi été constituée. Après avoir validé notre méthodologie pour la caractérisation externe de la mimique, l’analyse des muscles peauciers par l’IRM a été réalisée sur 10 hémifaces parmi les sujets sains issus de la cohorte. Cette caractérisation a fait appel, à partir d’une anatomie in vivo, à une modélisation de certains muscles peauciers (zygomaticus major en particulier) afin d’extraire des paramètres morphologiques, de réaliser une analyse plus fine de la morphologie musculaire en 3 dimensions, et d’apporter une meilleure compréhension du comportement cinématique du muscle dans différentes positions. Par son intégration dans un questionnement plus vaste :- comment caractériser objectivement la mimique faciale ? - quels sont les indicateurs qualitatifs et quantitatifs de la mimique que nous pouvons recueillir, et comment réaliser ce recueil ? - comment utiliser les développements technologiques dans les applications cliniques ? Ce travail constitue une étape préliminaire à d’autres travaux. Il pourra fournir des données de référence à des fins de modélisation, de simulation de la mimique faciale, ou de développements d’outil de mesures pour le suivi et l’évaluation des déficits de la mimique facialeThe aim of this research is to study facials mimics movements and to correlate externat soft tissue (i.e., cutaneous) movement during facial mimics with internal (i.e., facial mimic muscle) movement. The entire facial mimicry couldn't be studied, that's why relevant movements had been selected. Those movements were characterised by a clinically qualitative analysis in 23 young healthy volunteers. The analysis was performed with video recordings including scaling derived from the FACS (Facial Action Coding System). After the validation of external characterisation by this method, internal characterisation of the mimic facial muscle was carried out in 10 volunteers. A modelization of selected facial mimic muscle as Zygomaticus Major was achieved. With this work, morphological parameters could be extracted, 3D morphometric data were analysed to provide a better understanding of cinematic behaviour of muscle in different positions.This research is included in the Simovi Project, which aims to determine to what extent a facial mimic can be evaluated objectively, to select the qualitative and quantitative indicators for evaluation of mimic facial disorders, and to transfer our technological developments in clinical field. This research is a first step and provides data for simulation or developments of measurement tools in evaluation and follow-up of mimic facial disorders
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Héraud, Sandrine. "Adaptation de méthodes biophysiques et biomécaniques pour l'exploration des peaux reconstruites in vitro." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10307.
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On entend par substitut dermo-épidermique un épiderme reconstruit à la surface d'un derme équivalent composé de fibroblastes cultivés classiquement dans un biomatériau support, souvent à base de collagène poreux ou sous forme de gel. Ce support possède ses propres propriétés biomécaniques, influant sur la réponse biomécanique globale des peaux reconstruites, nous nous sommes donc intéressés à un modèle de peau reconstruite sans support, dans lequel le derme équivalent est « auto-assemblé » par les fibroblastes néosynthétisant leur propre matrice extracellulaire (MEC). Notre premier objectif a été d'optimiser et de caractériser ce modèle auto-assemblé en termes de structure, de reproductibilité et de fonctionnalité. Notre second objectif a été d'adapter aux peaux reconstruites in vitro (PR) des outils traditionnellement utilisés pour des études in vivo, pour explorer leurs propriétés biophysiques et biomécaniques. Ces outils permettent une exploration morphologique à des résolutions différentes avec l'échographie, la tomographie à cohérence optique (OCT) et la microscopie confocale à balayage et une exploration fonctionnelle des propriétés biomécaniques des PR par cutométrie. Ces données biophysiques ont ensuite été analysées par rapport aux résultats en histologie, immunohistologie et microscopie électronique à transmission. La cinétique de culture du modèle auto-assemblé sur un temps prolongé a montré la grande stabilité de l'épiderme et le remodelage continuel de la MEC avec notamment l'augmentation des fibres de collagène et d'élastine. Au temps de culture de référence sélectionné, correspondant à l'obtention de la différenciation terminale de l'épiderme, nous avons démontré la reproductibilité des épaisseurs de l'épiderme et du derme en histologie et en OCT, de la maturité de l'épiderme et de la jonction dermo-épidermique et de l'expression dermique de l'élastine colocalisée avec la fibrilline. Sur le plan fonctionnel, nous avons démontré la fonction barrière de l'épiderme via l'imperméabilité du stratum corneum et des jonctions serréesA skin equivalent consist of a epidermis reconstructed on the top of a dermis equivalent classically composed of fibroblasts cultured into a biomaterial scaffold which is often a collagen gel or sponge. This scaffold hold its own mechanical properties, influencing the global skin equivalent biomechanical response, so we choose to develop a scaffold-free skin equivalent (SFSE), based on the ability of fibroblasts to synthezise their own extracellular matrix. Our first objective was to optimize and characterize the structure, the reproducibility and functionality of this scaffold-free model. Our second goal was to adapt biophysical and biomechanical tools classically used for in vivo evaluation to in vitro skin equivalents. Their morphology was explored with different resolutions using echography, optical coherence tomography (OCT) and laser scanning microscopy whereas biomechanical functionality was evaluate by a suction test, the cutometry. This biophysical data were compared to more classical histological, immununohistological and transmission electronic microscopy results. The long-term culture of the scaffold-free model showed the good stability of epidermis and the continuous remodelling of MEC with notably an increase of collagen and elastin fibers. We selected a reference culture time, corresponding to the complete terminal differentiation of epidermis. At this culture time, we showed the epidermis and dermis thickness reproducibity in histology and OCT, the constant epidermis and dermo-epidermal junction maturity and the dermal expression of elastin, colocalized with fibrillin. The barrier function of epidermis was also demonstrated via stratum corneum and tight junctions impermeability
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(5930606), Vivek Dharmangadan Sree. "Multiscale and Multiphysics Modeling of Pressure Driven Ischemia and Ulcer Formation in the Skin." Thesis, 2019.
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Pressure ulcers (PU) are localized damage to skin and underlying tissue that
forms in response to ischemia and subsequent hypoxia from external applied mechanical loads such as pressure. We demonstrate how a multiscale and multiphysics finite element model can capture the process of pressure ulcer formation.
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(9183377), Taeksang Lee. "Improving Reconstructive Surgery through Computational Modeling of Skin Mechanics." Thesis, 2020.
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Excessive deformation and stress of skin following reconstructive surgery plays a crucial role in wound healing, often leading to complications. Yet, despite of this concern, surgeries are still planned and executed based on each surgeon's training and experience rather than quantitative engineering tools. The limitations of current treatment planning and execution stem in part from the difficulty in predicting the mechanical behavior of skin, challenges in directly measuring stress in the operating room, and inability to predict the long term adaptation of skin following reconstructive surgery. Computational modeling of soft tissue mechanics has emerged as an ideal candidate to determine stress contours over sizable skin regions in realistic situations. Virtual surgeries with computational mechanics tools will help surgeons explore different surgeries preoperatively, make prediction of stress contours, and eventually aid the surgeon in planning for optimal wound healing. While there has been significant progress on computational modeling of both reconstructive surgery and skin mechanical and mechanobiological behavior, there remain major gaps preventing computational mechanics to be widely used in the clinical setting. At the preoperative stage, better calibration of skin mechanical properties for individual patients based on minimally invasive mechanical tests is still needed. One of the key challenges in this task is that skin is not stress-free in vivo. In many applications requiring large skin flaps, skin is further grown with the tissue expansion technique. Thus, better understanding of skin growth and the resulting stress-free state is required. The other most significant challenge is dealing with the inherent variability of mechanical properties and biological response of biological systems. Skin properties and adaptation to mechanical cues changes with patient demographic, anatomical location, and from one individual to another. Thus, the precise model parameters can never be known exactly, even if some measurements are available. Therefore, rather than expecting to know the exact model describing a patient, a probabilistic approach is needed. To bridge the gaps, this dissertation aims to advance skin biomechanics and computational mechanics tools in order to make virtual surgery for clinical use a reality in the near future. In this spirit, the dissertation constitutes three parts: skin growth and its incompatibility, acquisition of patient-specific geometry and skin mechanical properties, and uncertainty analysis of virtual surgery scenarios.
Skin growth induced by tissue expansion has been widely used to gain extra skin before reconstructive surgery. Within continuum mechanics, growth can be described with the split of the deformation gradient akin to plasticity. We propose a probabilistic framework to do uncertainty analysis of growth and remodeling of skin in tissue expansion. Our approach relies on surrogate modeling through multi-fidelity Gaussian process regression. This work is being used calibrate the computational model against animal model data. Details of the animal model and the type of data obtained are also covered in the thesis. One important aspect of the growth and remodeling process is that it leads to residual stress. It is understood that this stress arises due to the nonhomogeneous growth deformation. In this dissertation we characterize the geometry of incompatibility of the growth field borrowing concepts originally developed in the study of crystal plasticity. We show that growth produces unique incompatibility fields that increase our understanding of the development of residual stress and the stress-free configuration of tissues. We pay particular attention to the case of skin growth in tissue expansion.
Patient-specific geometry and material properties are the focus on the second part of the thesis. Minimally invasive mechanical tests based on suction have been developed which can be used in vivo, but these tests offer only limited characterization of an individual's skin mechanics. Current methods have the following limitations: only isotropic behavior can be measured, the calibration problem is done with inverse finite element methods or simple analytical calculations which are inaccurate, the calibration yields a single deterministic set of parameters, and the process ignores any previous information about the mechanical properties that can be expected for a patient. To overcome these limitations, we recast the calibration problem in a Bayesian framework. To sample from the posterior distribution of the parameters for a patient given a suction test, the method relies on an inexpensive Gaussian process surrogate. For the patient-specific geometry, techniques such as magnetic resonance imaging or computer tomography scans can be used. Such approaches, however, require specialized equipment and set up and are not affordable in many scenarios. We propose to use multi-view stereo (MVS) to capture patient-specific geometry.
The last part of the dissertation focuses on uncertainty analysis of the reconstructive procedure itself. To achieve uncertainty analysis in the clinical setting we propose to create surrogate and reduced order models, especially principal component analysis and Gaussian process regression. We first show the characterization of stress profiles under uncertainty for the three most common flap designs. For these examples we deal with idealized geometries. The probabilistic surrogates enable not only tasks such as fast prediction and uncertainty quantification, but also optimization. Based on a global sensitivity analysis we show that the direction of anisotropy of skin with respect to the flap geometry is the most important parameter controlled by the surgeon, and we show hot to optimize the flap in this idealized setting. We conclude with the application of the probabilistic surrogates to perform uncertainty analysis in patient-specific geometries. In summary, this dissertation focuses on some of the fundamental challenges that needed to be addressed to make virtual surgery models ready for clinical use. We anticipate that our results will continue to shape the way computational models continue to be incorporated in reconstructive surgery plans.
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Tavares, Liliana Patrícia da Veiga Durão Barbosa. "Caracterização da pele humana in vivo para melhor compreender a pele do doente obeso." Master's thesis, 2012. http://hdl.handle.net/10437/2871.
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Orientação : Luís Monteiro RodriguesO impacto da obesidade na fisiopatologia da pele humana parece relacionar-se com diversas dermatoses, resultado da alteração da sua fisiologia normal, incluindo alterações na função barreira e na função de “envelope”. Contudo, a informação disponível é ainda escassa devido às diversas complexidades do tema. Este estudo pretende contribuir para a definição de uma metodologia de abordagem experimental para estudar, de forma objetiva, as alterações funcionais que caracterizam a pele obesa. O presente estudo, transversal, incluiu 28 voluntárias, do sexo feminino, saudáveis, com idade média 23±5 anos de idade, após consentimento informado. Foi realizada uma única medição de caracterização das diversas funções cutâneas obtidas por meios não invasivos em condições controladas. As variáveis consideradas relevantes foram, a hidratação (superficial e profunda) a função de barreira e o comportamento biomecânico, medidos em 4 áreas anatómicas distintas. Através do SPSS (v 20.0) realizámos uma análise estatística univariada com cálculo de medidas de tendência central e de dispersão. Recorremos aos testes de Pearson e de Spearman, para as variáveis que seguiam, ou não, uma distribuição normal, respectivamente, adotando um grau de confiança de 95% . Os resultados permitem propor uma metodologia para o estudo da pele, aplicável ao doente obeso, incluindo a escolha das áreas anatómicas e das variáveis adequadas ao objetivo pretendido.
The impact of obesity in the pathophysiology of human skin seems to be related with various dermatoses, resulting from the change in its normal physiology, including changes in barrier function and the “envelope”function. However, the available information is still scarce because of the many complexities of the subject. This study pretends to contribute to the definition of a methodology for the experimental approach to study objectively the functional changes that characterize the obese skin. This transversal study included 28 volunteers, female, healthy, average age 23 ± 5 years, after informed consent. We performed a single measurement of skin characterization of the various functions obtained by non-invasive under controlled conditions. The variables considered as relevant, hydration (superficial and deep) barrier function and biomechanical behavior, measured at four different anatomical areas. Through the SPSS (v 20.0) conducted a univariate statistical analysis to calculate measures of central tendency and dispersion. We use the Pearson test and Spearman for variables that followed or not, a normal distribution, respectively, assuming a confidence level of 95%. The results allow us to propose a methodology for the study of the skin, apply to obese patients, including the choice of the anatomical areas and variables appropriate to the intended goal.
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Jiun-Shian, Chang, and 張俊賢. "Biomechanical Analysis of Movements that Children Skip Rope on Different Frequencies." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/77834361655121694722.
Full textAbstract:
碩士國立臺北教育大學
體育學系碩士班
96
Abstract The purpose of this study was to investigate the changes in kinematical and dynamic parameters among different frequency levels of 90 time/min, 120 time/min, 132 time/min, and 150 time/min in rope.The experiment chose ten male students from the Min Quan Elementary School to be experiment subjects（aged 12.2±0.42, height of 151.7±5.34, and weight of 45.1±8.22）. A Meqa Speed25K high-spped camera（100Hz）and an AMTI force plate（1000Hz）were used to simultaneously capture kinematical and dynamic parameters of the body movements and legs in one action cycle of rope jumping, and divided rope jumping into three period. The periods are take-off, landing and air. Kinematical parameters are filmed through the camera , then the obtained film undergoes Two Dimensional Direct Linear Transformation（2D-DLT）by the Kwon 3D movement analysis software, in order to obtain the paraments such as the position of center of gravity, speed, displacement, and leg joint angle.Signals from force plate passes through the amplifier to 16- frequency multi-functional receiver box and a A/D analog-digital signal transformer, then the original signal is processed by DASY LAB 6.0 software to calibrate modular and low-pass filtering（10Hz）and calculate the three-dimensional ground reaction force Body weight（B.W.）is used as the basis for standardization to obtain ground reaction force value and impulse values. The resulting data underwent one-way ANOVA via SPSS 12.0 statistics software to compare whether there was a significant different in body kinematical and dynamic paraments for different movement frequency of rope jumping. If there is a significant difference（p<.05）, then the LSD method would be utilized to conduct post-analysis. The level of significamce for this experiment was set to α=.05. This study finds： ㄧ、Different frequency of rope jumping affect the three lower extremity joints in the lowest position of center of gravity. Faster frequency, smaller the three lower extremity joints. The three lower extremity joints in the lowest position of center of gravity both attained significant different（p<.05）. 二、Different frequency of rope jumping affect the maximal joint velocity of hip and time to maximal joint velocity of hip.Faster frequency, slower the the maximal joint velocity of hip and time to maximal joint velocity of hip.Various frequency both attained significant different（p<.05）. 三、Different frequency of rope jumping affect the vertical displacement of center of gravity. Faster frequency, fewer the vertical displacement of center of gravity. Various frequency in landing and jumping both attained significant different （p<.05）. 四、Different frequency of rope jumping affect the time of landing. Faster frequency, less the time of landing.Various frequency attained significant different（p<.05）. 五、Different frequency of rope jumping affect the impulse of landing. Faster frequency, less the impulse .Various frequency attained both significant different （p<.05）. 六、Different frequency of rope jumping affect the landing maximum rate. Faster frequency, more the landing maximum rate.Various frequency attained significant different（p<.05）. The conclusions are attained through the discussion of the findings : with the increasing of frequency in rope jumping,we should reduce the joint angle of three lower extremity joints before jumping and decrease the jumping height, in order to increase the speed of movement. In addition, the landing maximal load rate are increasing with frequency，for rookies, because they are not familiar with physical adjustment, it is not only impossible increasing the speed of movement, but it is also impossible buffering the impact from vertical ground reaction force.If rope jumping keeps high frequency long time, it results in greater probability of injury to the lower limbs.