Применение метода конечных элементов в процессе математического моделирования в урологии

The article presents data on possibility of the application of the method of finite elements (FEM) in the mathematical modeling of various diseases of the organs of the urogenital system, their diagnostics and treatment. Special attention was paid to the prospects of application of FEM for modelling methods of surgical treatment of diseases of the kidneys and urinary tract.В статье представлены данные о возможностях применения метода конечных элементов (МКЭ) в математическом моделировании различных заболеваний органов мочеполовой системы, их диагностики и лечения. Особое внимание уделено перспективам применения МКЭ для моделирования методов оперативного лечения заболеваний почек и мочевыводящих путей

Détection du cancer de la peau par tomographie d'impédance électrique

RÉSUMÉ Au cours des trente dernières années, l’augmentation du taux d’incidence du cancer de la peau a été la plus importante parmi tous les cancers. Le diagnostic précoce du cancer de la peau s’avère important pour minimiser les risques d’évolution en cancer généralisé. Ce diagnostic implique habituellement une inspection visuelle suivie d’une biopsie si la lésion est jugée suspecte par le clinicien. Des études récentes indiquent que le quart des lésions cancéreuses ne sont pas détectées à un stade précoce diminuant ainsi le pronostic du patient. De plus, plusieurs lésions biopsiées s’avèrent non cancéreuses, augmentant ainsi les risques d’infection tout en causant un stress inutile au patient dans l’attente des résultats histopathologiques. Pour détecter précocement le cancer de la peau, une nouvelle technique biomédicale s’avère prometteuse : la tomographie d’impédance électrique (TIE). La TIE est une technique d’imagerie médicale qui permet de visualiser la distribution de conductivité électrique d’une section du corps. Celle-ci se base sur le principe que les propriétés électriques de chaque tissu biologique varient de façon spécifique en fonction de la fréquence. Les images sont reconstruites à partir d’une série de mesures acquises à l’aide d’électrodes placées autour de la région d’intérêt. Ces mesures sont effectuées en utilisant toutes les combinaisons possibles de quatre électrodes : deux pour appliquer un courant de faible amplitude et deux autres pour mesurer la tension résultante. Comme les propriétés électriques des lésions cancéreuses et non cancéreuses diffèrent en fonction de la fréquence, les images de conductivité obtenues par TIE permettraient de les discriminer objectivement. L’objectif général de ce projet de doctorat consiste à développer un système de TIE permettant de détecter le cancer de la peau. Les objectifs spécifiques sont : 1) développer un modèle par éléments finis de la peau, 2) développer les algorithmes de reconstruction d’images, 3) adapter un système de TIE au contexte dermatologique et 4) valider le système en effectuant des tests expérimentaux. ----------ABSTRACT Over the past thirty years, skin cancer incidence rate has increased the most significantly among all cancers. Early stage skin cancer diagnosis is essential to minimize risks of developing metastases. Diagnosis usually involves visual inspection followed by histopathological examination if the lesion is suspected malignant by the clinician. Recent studies however suggest that a quarter of lesions remain undetected at an early stage which adversely affects the patient’s prognosis. Furthermore, many excised lesions are found not cancerous increasing risks of infection and causing unnecessary stress to the patient awaiting histopathological results. For early stage skin cancer diagnosis, a new biomedical technique seems promising: electrical impedance tomography (EIT). EIT is a medical imaging technique used to visualize the electric conductivity distribution of a body segment. EIT is based on the principle that electrical properties of every biological tissue specifically vary as a function of frequency. Images are reconstructed from a set of measurements acquired with electrodes applied around the region of interest. Measurements are performed using all possible combinations of four electrodes: two are used to apply a low amplitude current while two others are used to measure the resulting voltage. Since malignant and benign lesions have different cellular characteristics, their impedance signature as a function of frequency differs and they can therefore be objectively discriminated by EIT. The main objective of this PhD project is to develop an EIT system for skin cancer screening. The specific objectives are: 1) to develop a finite element model of the skin, 2) to develop image reconstruction algorithms, 3) to adapt an EIT system to the dermatology context, and 4) to validate the system experimentally. Since no EIT system has been developed for skin cancer screening, a finite element model of the skin was first developed to study the electrical behavior of the skin, identify optimal frequencies to discriminate lesions, and solve the forward problem of EIT

Гармонические перспективы реографии

The review briefly describes the main ways of rheography development. Particular emphasis is laid on the practically forgotten and newly revived method of the harmonic analysis of rheograms. The development of electronics and computed methods of data processing could unveil the potential of this direction of rheography and consider prospects for developing new diagnostic approaches on the basis of a multicyclic harmonic analysis of bioimpedance.В обзоре кратко описаны основные пути развития реографии. Особое внимание уделено практически забытому и вновь возрожденному методу гармонического анализа реограмм. Развитие электроники и компьютерных методов обработки данных позволило раскрыть потенциал этого направления реографии и рассмотреть перспективы разработки новых диагностических подходов на основе мультицикличного гармонического анализа биоимпеданса

Active and Passive Biomechanical Measurements for Characterization and Stimulation of Biological Cells

From a physical perspective biological cells consist of active soft matter that exist in a thermodynamic state far from equilibrium. Not only in muscles but also during cell proliferation, wound healing, embryonic development, and many other physiological tasks, generation of forces on the scale of whole cells is required. To date, cellular contractions have been ascribed to adhesion dependent processes such as myosin driven stress fiber formation and the development of focal adhesion complexes. In this thesis it is shown for the first time that contractions can occur independently of focal adhesions in single suspended cells. To measure mechanical properties of suspended cells the Optical Stretcher – a dualbeam laser trap – was used with phase contrast video microscopy which allowed to extract the deformation of the cell for every single frame. For fluorescence imaging confocal laser scanning microscopy was employed. The ratio of the fluorescence of a temperature sensitive and a temperature insensitive rhodamine dye was utilized to determine the temperatures inside the optical trap during and after Optical Stretching. The rise in temperature at a measuring power of 0.7W turned out to be enough to open a temperature sensitive ion channel transfected into an epithelial cell line. In this way a massive Ca2+ influx was triggered during the Optical Stretcher experiment. A new setup combining Optical Stretching and confocal laser scanning microscopy allowed fluorescence imaging of these Ca2+ signals while the cells were deformed by optically induced surface forces, showing that the Ca2+ influx could be manipulated with adequate drugs. This model system was then employed to investigate the influence of Ca2+ on the observed contractions, revealing that they are partially triggered by Ca2+. A phenomenological mathematical model based on the fundamental constitutive equation for linear viscoelastic materials extended by a term accounting for active contractions allowed to quantify the activity of the measured cells. The skewness and the median of the strain distributions were shown to depend on the activity of the cells. The introduced model reveals that even in measurements, that seemingly are describable by passive viscoelasticity, active contractililty might be superimposed. Ignoring this effect will lead to erroneous material properties and misinterpretation of the data. Taken together, the findings presented in this thesis demonstrate that active processes are an essential part of cellular mechanics and cells can contract even independently of adhesions. The results provide a method that allows to quantify active contractions of suspended cells. As the proposed model is not based on specific assumptions on force generating processes, it paves the way for a thorough investigation of different influences, such as cytoskeletal structures and intra-cellular signaling processes, to cellular contractions. The results present an important contribution for better mechanical classification of cells in future research with possible implications for medical diagnosis and therapy

Cells and Materials for Disease Modeling and Regenerative Medicine

Materials science and engineering are strongly developing tools with increasing impact in the biotechnological and biomedical areas. Interestingly, research in molecular and cellular biology is often at the core of the design and development of materials-based approaches, providing biological rationale. Focused on research relying on biology–materials interaction, IJMS launched a Special Issue named “Cells and Materials for Disease Modeling and Regenerative Medicine”. The aim of the Special Issue was to generate a compilation of in vitro and in vivo strategies based on cell–material interactions. This book compiles the papers published in that Special Issue and includes a selection of six original scientific experimental articles and six comprehensive reviews. We are convinced that this collection of articles shows representative examples of the state of the art in the field, unveiling the relevance of materials research in generating new regenerative medicine and disease modeling approaches

Bovine Science

Bovine Science - Challenges and Advances presents up-to-date knowledge of bovine health, covering both introductory topics and more advanced concepts. Chapters cover such topics as new techniques in bovine science and development, health and risk factors and diagnosis of disease in bovines, and production and reproductive technologies and advancements