Applications of Magnetic Resonance to Current Detection and Microscale Flow Imaging

Magnetic resonance has evolved into a remarkably versatile technique, with major applications in chemical analysis, molecular biology, and medical imaging. Despite these successes, there are a large number of areas where magnetic resonance has the potential to provide great insight but has run into significant obstacles in its application. The projects described in this thesis focus on two of these areas. First, I describe the development and implementation of a robust imaging method which can directly detect the effects of oscillating electrical currents. This work is particularly relevant in the context of neuronal current detection, and bypasses many of the limitations of previously developed techniques. The approach rests on a resonant interaction between an applied radiofrequency field and an oscillating magnetic field in the sample and, as such, permits quantitative, frequency-selective measurements of current density with sensitivity near the threshold required for the detection of neuronal currents. The second part of this thesis focuses on novel methodology and applications for remotely detected magnetic resonance. Remote detection separates the encoding and detection steps of a traditional magnetic resonance experiment in both time and space, allowing for high-resolution time-of-flight imaging of very small volumes of flowing nuclei. Following a discussion of the recent developments in methodology and hardware design, I present a series of remotely detected imaging experiments within microporous bead packs and organic polymer monoliths. These techniques allow for the acquisition of high-resolution images which correlate velocity, spin relaxation, and time-of-flight in previously inaccessible microscale systems