Novel multi-channel transmission line coil for high field magnetic resonance imaging

Radiofrequency (RF) coils are the antenna-like devices used in magnetic resonance imaging (MRI) to inductively excite and receive the nuclear magnetic resonance (NMR) signal in anatomy. This nuclear magnetic induction is most efficient at the field strength dependent Larmor frequency for a nuclear species. Coils must resonate at Larmor frequencies of 300 MHz or more to take advantage of the signal-to-noise benefits of 7T+ MRI. In high water content tissue dielectrics however, the wavelengths at these frequencies are 12 cm and less, significantly shorter than human anatomic dimensions. One consequence of these short wavelengths is a highly non-uniform RF excite field. In this investigation, we aim to mitigate this problem through a novel coil element design. The traditional microstrip line element is modified into a multi-section alternating impedance configuration to homogenize the magnetic field over the coil length. Feasibility of this approach is numerically simulated, and then empirically validated by phantom and human imaging.