Date of Award
Doctor of Philosophy
Techniques have been both analyzed and developed for the estimation of a number of important haemodynamic parameters (including velocity, volume flow rate and shear rate) using a magnetic resonance (MR) scanner. Accurate estimation of these parameters is important because information about the haemodynamic state may (1) aid our understanding of vascular disease processes; and (2) provide a clinically-useful test for the presence of vascular disease.;The objectives of this thesis are: (1) the development of techniques that are necessary for the accurate and precise simulation of physiological flow waveforms in in vitro MR research; (2) the furthering of our understanding of the effects that temporal and convective accelerations have on MR phase contrast techniques; and (3) the introduction of a new technique for accurately measuring the fluid shear rate at the vessel wall.;The key components of the in vitro model system were a flow simulator and a flow rate sensor. The performance of a computer-controlled flow simulator was evaluated to ensure that both constant and arbitrary pulsatile flow waveforms could be generated within the MR scanner bore. The limitations imposed by the effects of the compliant tubing and piston turnaround were identified and overcome. Second, a volume-flow rate sensor was adapted so that the flow waveform within the magnet bore could be independently quantified.;The effect of acceleration on the accuracy of phase contrast (PC) velocity measurements was investigated and found to cause a class of displacement artifacts in the velocity estimates. A formalism was developed to explain these errors and verified experimentally. The effects of acceleration between PC acquisitions was investigated for gated techniques, and found to cause a frequency-domain filtering of the time series velocity estimates. The filter kernels are described analytically and verified experimentally.;Finally, this thesis presents a novel technique for estimating the fluid shear rate at the vessel wall. The procedure involved collecting the entire velocity distribution within each voxel using Fourier-encoded velocity imaging, and then inverting this distribution to estimate the velocity profile within the voxel. Simulation and preliminary experiments have shown that this technique makes accurate shear rate estimates near the wall.
Frayne, Richard, "Estimation Of Haemodynamic Parameters Using Magnetic Resonance Imaging" (1994). Digitized Theses. 2450.