Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 5 uppsatser.

Dissertation (Ph.D.) --University of Texas Graduate School of Biomedical Sciences at San Antonio, 2008. / Vita. Includes bibliographical references.

This work develops an empirical method for investigation of the flow properties of blood and applies it to a clinically oriented problem. The development focuses on the characterization of the flow properties of a blood sample. According to the theory of continuum mechanics the steady state flow properties of a material are characterized completely by its constitutive (Burchfield, 1972) function which relates the shear stress measured in a rheometer to the shear rate and hematocrit of the sample. Eleven functions derived from various sources were examined for their ability to fit flow data from thirty—one normal individuals, eleven of whom were using oral contraceptives. (The remainder were not using any drugs). A shear rate range of 0.0312 to 124 s⁻¹ was used at hematocrits from 0.29 to 0.55. A non-linear curve fitting procedure allowed an ordering of the functions to be established with respect to their goodness of fit. The function first employed by Walburn and Schneck (1976), T = X₁ exp (X₂ H+X₄ /H²)D[sup 1-X₃] where T = shear stress, D = shear rate, H = hematocrit and X₁ to X₄ are adjustable parameters, was found to be the most successful. This constitutive function was then used to examine data obtained from a population of normal women at various times during the menstrual cycle, as a hemorheological cycle had been reported to occur over this period. The concentrations of several plasma proteins were also determined and plotted over time. No evident cycle of hemorheological properties or protein concentrations was found. / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate

Time-resolved velocity information of carotid blood flow can be used to estimate haemodynamic conditions associated with carotid artery disease leading to stroke. MRI provides high-resolution measurement of such information but long scan time limits its clinical application in this area. In order to reduce scan time the MRI signal is often undersampled by skipping part of the signal during data acquisition. The aim of this work is to implement and evaluate different undersampling techniques for carotid velocity measurement on a 1.5 T clinical scanner. Most recent undersampling techniques assume spatial and temporal redundancies of real time-resolved MRI signal. In these techniques different undersampling strategies were proposed. Prior information or different assumptions of the nature of true signal were used in signal reconstruction. A brief review of these techniques and details of a representative technique, known as k-t BLAST, are presented. Another undersampling scheme, termed ktVD, is proposed to use predesigned undersampling patterns with variable sampling densities in both temporal and spatial dimensions. It aims to collect enough signal content at the signal acquisition stage and simplify signal reconstruction. Fidelity of the results from undersampled data is affected by many factors, such as signal dynamic content, degree of signal redundancy, noise level, degree of undersampling, undersampling patterns, and parameters of post-processing algorithms. Simulations and in vivo scans were conducted to investigate the effects of these factors in time-resolved 2D scans and time-resolved 3D scans. The results suggested velocity measurement became less reliable when they were obtained from less than 25% of the full signal. In time-resolved 3D scans the signal can be undersampled in either one or two spatial dimensions in addition to the temporal dimension. This allows more options in the design of undersampling patterns, which were tested in vivo. In order to test undersampling in three dimensions in high resolution 3D scans and measure velocity in three dimensions, a flow phantom was also scanned at high degrees of undersampling to test the proposed method.

Ho Sin Yee, Stella. / "August 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 167-193). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 161-175).

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2007. / Härtill 4 uppsatser.

Thesis (M.S. )--University of Tennessee Health Science Center, 1999 / Title from title page screen (viewed on July 16, 2008). Research advisor: Eugene C. Eckstein. Document formatted into pages (91 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 73-77).

Thesis (doctoral)--Rijksuniversiteit te Utrecht.

An experimental animal model was developed to study and define the relationship between the blood flow and the marrow cavity pressure of bone. The study was carried out in 24 rabbits and 32 dogs under nembutol anesthesia. A multichannel physiograph was used to record simultaneously the systemic blood pressure, bone blood flow, marrow cavity pressure of bone and time sequence. The systemic blood pressure was measured by cannulating a brachial or carotid artery. The bone blood flow was measured by cannulating the nutrient vein and/or the nutrient artery. The marrow cavity pressure was measured by inserting a steel cannula through a drill hole in the cortex into the marrow cavity. The bones studied were mainly the tibia and femur. During the normal control condition, the marrow cavity pressure was found to have a wide range from animal to animal. In the rabbits, the range was from 20 to 60 mm. Hg. (15 to 50 percent of the systemic blood pressure). In the dogs, it ranged from 40 to 120 mm. Hg. (20 to 90 percent of the systemic blood pressure). However, the systemic blood pressure, intramedullary pressure and nutrient venous outflow were remarkably constant in a control period, therefore, their changes under experimental conditions were readily recordable. Various factors affecting bone circulation were studied. If the femoral vein is occluded the marrow cavity pressure rises and the nutrient venous outflow increases indicating venous congestion of bone. Nutrient artery occlusion causes a sharp fall in marrow cavity pressure coupled with a marked decrease in the nutrient venous outflow. Adrenalin and noradrenalin intravenous infusions produce a fall in marrow cavity pressure coupled with a decreased bone blood flow, despite an elevation in the systemic blood pressure. Isoproterenol hydrochloride generally causes a fall in the systemic blood pressure, widening of the pulse pressure, a fall in the marrow cavity pressure and a decrease in the nutrient venous outflow. Electrical sympathetic stimulation produces a fall in the marrow cavity pressure and a decrease in bone blood flow. Lumbar sympathectomy causes a rise in the marrow cavity pressure and an increase in the bone blood flow. Skeletal muscle contraction produces bone venous congestion with elevation of the marrow cavity pressure and increased nutrient venous outflow. Muscular relaxation causes a momentary sharp fall in the marrow cavity pressure to sub control levels before returning to the normal pressure. It is concluded that the marrow cavity pressure is bone blood flow dependent and reflects well the changes in the hemodynamics of bone. The narrow pressure rises if the arterial blood supply to bone increases or the venous congestion occurs in bone. The marrow pressure falls if the arterial blood supply to bone decreases or the venous drainage of bone is facilitated. / Surgery, Department of / Medicine, Faculty of / Graduate