The advantage of conventional loop coils without distributed capacitors – elongation for improved performance in 7T MRI

Motivation: At Ultra-High-Field, non-uniform currents have the potential to boost efficiency of loop coils at depth. However, possible advantages of non-uniform current naturally arising from short wavelength at Ultra-High-Field have not been investigated yet. Goal(s): To characterize the impact of non-uniform currents on SAR efficiency for different coil geometries and coil orientations relative to the main magnetic field, and evaluate the feasibility of using such coilsApproach: Analysis was performed using simulations and experimentsResults: A 62x280mm elongated loop provided higher SAR efficiency than a conventional loop, or a dipole, at depth, with flexibility. low coupling, similar SNR and transmit efficiency than a dipole. Impact: An elongated design of loops provided higher performance than conventional loops and dipoles in terms of SAR efficiency at depth, with flexibility, and low coupling. Results in this work provide a new avenue to explore in flexible coil design.