| Remarkable progress in radiofrequency (RF) coil design has been achieved over the last two decades, improving the performance of many magnetic resonance imaging (MRI) techniques, and facilitating numerous clinical and scientific applications. However, a rational general framework for optimizing RF coil design is still missing, especially at ultra-high field strength (UHF), where optimal coil configurations have yet to be determined. Recent studies on ultimate intrinsic signal-to-noise ratio (UISNR) -- that is, the maximum signal-to-noise ratio compatible with electrodynamic principles -- have established stepping stones towards such a framework. In particular, the ideal current patterns that achieve UISNR in a particular geometry may be used as a guide to optimize the pattern of conductors in a prospective RF coil design.;As an alternative to loop coils, electric dipole antennas have recently been introduced for use in MR signal generation and reception, and they have seen increasing use in UHF applications. As the field strength, and the corresponding operating frequency, of MR scanners increases, contributions of axially-directed currents to UISNR in the center of cylindrical objects become increasingly dominant, which suggests that properly configured dipole antennas should be strong performers at UHF. However, while various particular dipole antenna configurations have been proposed in the literature, optimality has yet to be demonstrated. Additionally, connections between potentially complex ideal current patterns and practical coil designs are only beginning to emerge.;The contributions presented in this dissertation demonstrate the utility of dipole antennas and explore their optimization in practice. A coil design framework for SNR optimization is introduced, which provides useful interpretations of the ideal current patterns for UISNR. Although most simulations and experiments described in the dissertation were carried out at 7 Tesla, the underlying design philosophy can be applied to any field strength, and could be especially relevant for even higher field strengths and operating frequencies. |
