Design and evaluation of Overhauser enhanced MRI visible markers

Abstract

This thesis deals with the theoretical principles, design and construction of a small-sized marker which is visible in magnetic resonance images. The nuclear magnetic resonance signal emitted by the marker is enhanced by the use of the Overhauser phenomenon.

Different marker configurations were designed and constructed. A point-like marker was coupled to the feeding cable by loop and loop-gap geometries, and circuit analogies were presented to the loop-gap geometry and to the Overhauser phenomenon. An elongated, cylindrical marker was realized by constructing a transmission-line marker where a microwave shield and tapered coupling were included in the design. The markers' feasibility in interventional use was demonstrated in phantom and in vitro experiments, and the loop-gap marker was used in high-resolution MR studies.