UCLA

The central theme of this thesis is the inherent signal response to flow effects in magneticresonance imaging (MRI). These effects can be seen as either an asset or a nuisance. The work detailed in the first specific aim exemplifies how flow effects can be used, by using arterial spin labeling to assess for peri-wound perfusion in and around foot ulcers of diabetic patient volunteers. Specific aims two and three aim to mitigate troublesome outflow artifacts in balanced steady-state free precession (bSSFP) imaging. Insight into the nature of k-space encoding in MRI is a prerequisite to posing solutions to address the problem. Therefore, I will review frequency and phase encoding in some detail to explain how outflow artifacts become misregistered during standard 2D bSSFP imaging. After the foundation of signal encoding is laid out, the work presented in the second specific aim narrates these effects as a through-slice aliasing, and proposes applying through-slice phase-encoding (“slice-encoding”) to localize outflowing spins from contaminating the target slice. This slice-encoding scheme provides a proof-of-concept for removing outflowing spins, however its practicality is limited as the breath-hold duration scales linearly with the number of encoding steps. Before discussing the third aim, the thesis will recap key concepts in making use of the spatially-varying phased-array channel sensitivity in MR imaging. The third specific aim explores the use of the NMR phased-array coil sensitivity profile to spatially encode for the outflowing spins, accelerating image acquisition relative to the slice-encoding steps approach. Aim 3 builds on the theory of parallel acquisition, but has novel features that are specific to goal of mitigating outflow artifact in bSSFP.