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Intra-Aortic Balloon Counterpulsation
Žbánková, Alena ; Tannenberg,, Milan (referee) ; Sekora, Jiří (advisor)
The thesis is concerned with intraaortic balloon counterpulsation, which serves as a supporting method for the operation of failing heart. In the teoretical part is described principle of this method, its effects and the basic indications and contraindications of using. In the practical part of this work is proposed method for detecting triggering points realized in graphical program LabVIEW. The program outputs are detected ends of T wave for balloon inflation and R wave for its deflation.
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Analysis of residual stresses in arterial wall
Novák, Kamil ; Fuis, Vladimír (referee) ; Burša, Jiří (advisor)
This thesis deals with computational modeling of the influence of residual stresses in idealized geometry of blood vessels and subsequent application of acquired knowledge to abdominal aortic aneurysm. In the terms of quality of the computational model, we reduced the uncertainties that are included in the computational model without considering the influence of residual stresses. The basic assumption of homogenization significant peaks of the stress between inner and outer vessel wall was met for each level of the computational model Methods that have been used are: deformation method (opening angle method), inverse mechanics of large deformations, fictitious temperature – for linear elastic material and hyperelastic material defined by the constitutive model. Numerical verification was carried out using program ANSYS.
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Influence of strain rate on stress-strain dependencies of aortic tissues
Slažanský, Martin ; Fuis, Vladimír (referee) ; Burša, Jiří (advisor)
The thesis deals with the influence of strain rate on stress-strain dependencies of aortic tissues to estimate the error of hyperelastic models, which are neglecting the viscoelastic effects that are typical for soft biological tissues. It was found by the experiment and the subsequent evaluation that in the range of the strain rate from 0,167 to 5,000 mm/s the influence of strain rate on stress-strain dependencies is negligible. The deviation by transition from experimental data to a constitutive model was significantly larger than the deviation between the data sets varying at different strain rates, which means that the use of stress-strain curves varying at different strain rates in given range of the strain rate has no effect on the resulting model. The best of analysis models that were examined in this thesis appears to be the Yeoh hyperelastic model using the FEM.
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Influence of the contrast medium iodine concentration on quality of the CT examination
RANŠOVÁ, Pavlína
Our work focused on determining absolute and relative density of various contrast agents in relation to iodine contents using in vitro and in vivo methods. It was documented that the relative density of contrast agents increases with the decreasing contents of iodine, i.e. density absolute values vary inversely as iodine content in these substances. Four various agents, bearing commercial names Visipaque 270, Visipaque 320, Ultravist 370 and Iomeron 400, in their original glass packing were used for our in vitro measurements. The measurements were carried out using CT equipment Emotion Duo (Siemens, Forchheim, Germany). Individual packing of the contrast agents were scanned by means of a standard protocol and under standard conditions. The obtained data were entered into tables. A retrospectively selected array of patients with standard scan of their stomachs was used for our in vivo measurements with a defined standard protocol using the same CT equipment and pressure injector CT 9000 Advantage (Liebel-Flarsheim, Mallinckrodt, the U.S.A.). The following data from 258 patients were recorded: age, sex, blood density after administering contrast agent in vitro on the level of diaphragm hiatus and on the bifurcation level, AP dimension of the patients on the hiatus level. Mean densities of the individual kinds of contrast agents were compared and a good correlation with the in vitro measurements was found out. The measured values were then analysed. The interdependence was studied in the measured densities and age, density changes measured on the hiatus level and on the bifurcation level for the individual contrast agents. The interdependence of the blood density on the AP dimension of the patients was also studied due to its practical use and it was documented that there is a good correlation of the decreasing density with the AP dimension as a simple parameter used instead of finding out patients{\crq} weights.
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Residual Strains of Arteries as Forensic Index
Adámek, T. ; Horný, L. ; Chlup, Hynek ; Žitný, R.
It has been known for long time that arteries are pre-strained in situ. These residual strains play crucial role in arterial load-bearing capacity. However, to the best of authors’ knowledge they have never been considered from forensics point of view. This paper concerns a possibility of employing the longitudinal pre-strain of human aortas as an indicator of human subject age. Lengths of abdominal aorta were measured within autopsies before and after segment resection. Longitudinal stretch ratio was calculated for 45 male and 12 female cadavers. It was found that both male and female data samples give approximately the same mean of the stretch ratio = 1.2. The correlation coefficients between the pre-strain and age were R=-0.7926, R=-0.8684 in male and female samples, respectively. Linear regression equation with confidence intervals was employed. The correlation between pre-strain and age seems to be suitable statistics to be used in forensic sciences.
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Konstitutivní modelování tepenné stěny
Horný, L. ; Chlup, Hynek ; Adámek, T. ; Zitny, R. ; Macková, H.
Inflation tests and uni–axial extension tests of arterial tissue were performed. Experimental data were used in nonlinear regression analysis to identify material model. Arterial tissue was assumed to be incompressible hyperelastic material. 5–parameter strain energy density function based on combination of isotropic Neo–Hookean expression and Fung–type orthotropic expression was used. Computational model for material parameters identification was based on thick–wall tube with axial pre–strains. Residual strains were included. Internal structure of arterial wall was not considered. Fitted material models correspond to experimental data very well.
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Zbytková deformace v bifurkaci lidské aorty
Adámek, T. ; Horný, L. ; Chlup, Hynek ; Franta, L.
At the present paper we report values of opening angles in human aortic bifurcations. A standard method of opening angle measurement was used. Three aortas were measured. Ten samples were excised from each aorta. Three rings were obtained from abdominal aorta close to the bifurcation, arteria iliaca communis dextra and sinistra and one form the bifurcation. The last one was composed of two rings, left and rignt, which were measured together. The residual strains were occurred in human aortic bifurcations and had different values in the left and the right branch of the bifurcated artery. The results of at the bifurcation can be influenced by fact that the branches of iliac arteries are still intergrown here. Two kinds of the opening angle investigation at the bifurcation were tested, a bifurcation septum fixed method and a circular sector fixed method. But both revealed differences in the opening angle values at the bifurcation.
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