New ultrasound techniques for investigating the non-Newtonian characteristics of whole blood
Series: Canadian theses = Thèses canadiennes
Publisher: National Library of Canada = Bibliothèque nationale du Canada
Published: 1993
Place of publication: Ottawa
Language: eng
Format: Microform
Description: This thesis describes the development and evaluation of new techniques for investigating the non-Newtonian characteristics of blood.  It also presents the results of measurements on whole porcine blood and discusses their interpretation.
    Ultrasound B-mode imaging (7 MHz) was used to measure blood echoicity and velocity profiles simultaneously as they developed with axial distance for a steady flow of 28% hematocrit whole blood flowing in a long (>60D) large diameter (D=2.54 cm) tube.  Velocity profiles were measured using cross correlation technique between successive digitized images, and from these shear rate profiles were calculated.  Echoicity profiles were determined from the digitized images by temporal averaging along the flow axis.  Pulsed Doppler ultrasound (20 MHz) was also used to measure the velocity and relative power profiles at 60 D from the tube entrance.  The velocity profiles measured using B-mode were in good agreement with those measured using MRI as well as Doppler ultrasound.
    It was found that the echoicity increased with time up to a shear rate dependent upper limit; this limit seemed to drop as the shear rate increased and vice versa.  The rate of echoicity increase depended on the initial state of echoicity and either the applied shear rate (in the case of flowing blood) or the shear rate history (in the case of stagnant blood).  Any shear rate whether high or low would increase the rate of echoicity build up as long as this echoicity is less than the upper limit allowed by the applied shear rate.  Additional evidence confirming previous assumptions of the responsibility of erythrocyte aggregation for blood echoicity was found.
Notes: University Microfilms order no. UMI00396519.

Thesis (M.A.Sc.)--University of Toronto, 1992.

Includes bibliographical references.