No description available.

Thesis (doctoral)--Lund University, 1996. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1996. / Added t.p. with thesis statement inserted.

No description available.

In coronary artery bypass surgery the autologous saphenous vein is the most commonly used vascular graft. However, in a growing number of patients this vein is not available due to disease or availability. To date, there are no commercially available vascular grafts to replace the autologous saphenous vein. Nevertheless, it is widely accepted that a successful small diameter blood vessel alternative will be found using a tissue engineering approach. A photo-cross-linked biodegradable elastomer of acrylated star-poly(ε-caprolactone-co-D,L-lactide) (ASCP) has recently been developed. The elastomer possesses many desirable properties, such as manufacturability and mechanical properties, making it an interesting scaffolding material candidate for this application. To test the feasibility of the ASCP elastomer as a scaffolding material, a porous scaffold with 90% porosity was constructed using paraffin microbeads combined with an emulsion of ASCP prepolymer and water. Native arterial mechanical properties were matched with an 1800 Da ASCP elastomeric scaffold (ELAS 1800) having 85% porosity. In vitro degradation of scaffolds prepared with two different ASCP Mn (1800 and 4500 Da) was investigated for 8 weeks. Bulk hydrolysis was the mode of degradation regardless of configuration, with the porous scaffold degrading slower than the nonporous control. In addition, the ELAS 4500 scaffold also degraded faster than the ELAS 1800 scaffold with the same porosity. In order to promote the cellular response to this potential vascular scaffold, the surface of the elastomer was modified to enhance bovine coronary artery smooth muscle cell (SMC) attachment and proliferation. Base etching the surface was not as effective as adding a small peptide sequence Gly-Arg-Gly-Asp-Ser (GRGDS) known to enhance cell adhesion. The surface modifications did not change SMC phenotype as all surfaces expressed the contractile marker proteins smooth muscle α-actin and h-caldesmon. The SMCs also expressed these marker proteins when seeded on porous scaffolds. Finally, it was possible to integrate the porous scaffold into a biomimetic blood vessel design. With this initial testing, it appears that the ASCP elastomer is a feasible scaffolding material for small diameter blood vessel tissue engineering. Nevertheless, more detailed testing of mechanical properties and cell behaviour must be conducted to ascertain that the ASCP elastomer and the proposed biomimetic blood vessel design can be appropriate replacements for the autologous saphenous vein. / Thesis (Master, Chemical Engineering) -- Queen's University, 2007-11-18 20:27:30.635

No description available.

Thesis (M. S. in Biomedical Engineering)--Vanderbilt University, May 2007. / Title from title screen. Includes bibliographical references.

No description available.

In this dissertation, I investigated computing algorithms for automated retinal blood vessel detection. Changes in blood vessel structures are important indicators of many diseases such as diabetes, hypertension, etc. Blood vessel is also very useful in tracking of disease progression, and for biometric authentication. In this dissertation, I proposed two algorithms to detect blood vessel maps in retina. The first algorithm is based on integration of a Gaussian tracing scheme and a Gabor-variance filter. This algorithm traces the large blood vessel in retinal images enhanced with adaptive histogram equalization. Small vessels are traced on further enhanced images by a Gabor-variance filter. The second algorithm is called a radial contrast transform (RCT) algorithm, which converts the intensity information in spatial domain to a high dimensional radial contrast domain. Different feature descriptors are designed to improve the speed, sensitivity, and expandability of the vessel detection system. Performances comparison of the two algorithms with those in the literature shows favorable and robust results. Furthermore, a new performance measure based on central line of blood vessels is proposed as an alternative to more reliable assessment of detection schemes for small vessels, because the significant variations at the edges of small vessels need not be considered. The proposed algorithms were successfully tested in the field for early diabetic retinopathy (DR) screening. A highly modular code library to take advantage of the parallel processing power of multi-core computer architecture was tested in a clinical trial. Performance results showed that our scheme can achieve similar or even better performance than human expert readers for detection of micro-aneurysms on difficult images.

Mechanische Beanspruchungen verändern bei nahezu jeder Zelle ihre Funktion und ihre Form. Wir interessieren uns besonders für die durch mechanische Beanspruchungen hervorgerufene Effekte im Blutgefäßsystem, dessen Innenseite von den sogenannten Endothelzellen ausgekleidet ist, die eine Permeabilitätsbarriere zwischen Blut und Gewebe darstellen. Durch den Blutstrom sind diese Zellen permanent einer erheblichen mechanischen Beanspruchung ausgesetzt, die nicht nur ihre Form, sondern auch ihre Funktionen wesentlich verändert. Wir haben in unserem Labor einen experimentellen Aufbau entwickelt, mit dem wir erstmalig zeigen konnten, dass laminare Strömungen zu einer Verstärkung der endothelialen Barrierefunktion führen und so vermutlich der Entwicklung der Gefäßverkalkung entgegenwirken. Neben diesen Experimenten wird das neue System auch zur dynamischen Untersuchung der Zellhaftung auf Biomaterialien verwendet. / Mechanical loads change the function and morphology of nearly every cell. We are particularly interested in the effects of mechanical loads on the endothelial cells which line the inner surface of blood vessels and control the exchange of water and solutes between blood and tissue (barrier function). These cells are exposed permanently to mechanical forces from the blood stream, which induces changes not only in cell morphology but also in function. We have developed an experimental setup which allows the endothelial barrier function to be measured under defined flow conditions. We have demonstrated for the first time that laminar shear stress enhances the endothelial barrier function, and thus a possible explanation for the anti-arteriosclerotic effect. Importantly, our setup can also be used to dynamically test the adhesion of cells on biomaterials.