Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Physics

Supervisor

Chronik, Blaine A.

Abstract

Delta relaxation enhanced magnetic resonance (dreMR) is a field cycled magnetic resonance imaging method for quantitative molecular imaging. DreMR uses an insertable field cycling coil to exploit longitudinal dispersion of contrast agents producing signal proportional to their concentration. Assumptions in the development of dreMR included instantaneous ramping of the insert coil and perfectly homogeneous field shifts. Here we discard these assumptions and show that finite ramping and field inhomogeneities can impair proportionality to agent concentration and produce significant signal from background tissues. To mitigate these effects, a novel dreMR coil design method is developed employing a boundary element method designed layer to the system which corrects field inhomogeneities, maximizing the usable dreMR imaging region. While a dreMR coil has not yet been constructed for use on humans, with these improvements it is expected that human designs will be much more feasible allowing the extension of this method to clinical studies.

Summary for Lay Audience

Delta relaxation enhanced magnetic resonance (dreMR or “dreamer”) is an extension of magnetic resonance imaging (MRI) which allows the user to locate target molecules within the imaging subject. By use of an insertable electromagnetic coil and field dependent contrast agents, dreMR is able to produce images with signal proportional to local concentration of these agents. However, this is the idealized case where the coil is able to instantaneously produce a perfectly uniform magnetic field. In reality, this field contains imperfections and takes some finite period of time to produce. In this thesis we revisit the original derivations of dreMR with these parameters accounted for and find that they lead to a loss of proportionality to agent concentration and confound differentiation between background tissues and locations of agent. We discuss the feasibility of mitigating these effects and present an improved design method for dreMR coils which corrects field imperfections. Thus far a dreMR coil has not been constructed for use on humans. However, with these improvements it is expected that human designs will be much more feasible allowing the extension of this method to clinical studies.

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