Alternating impedance multi-channel transmission line resonators for high field magnetic resonance imaging

The multi-channel volume coil can be comprised of an array of transmission line elements that are operated as independent coils in typically multiple-channel transmit and receive configurations. In these designs, microstrip elements have been implemented as magnetic field generating elements. However, at high fields, short in vivo wavelengths and greater sample losses lead to RF in-homogeneities and inefficiencies. Optimization of these elements are required to overcome these challenges for desired MR applications. In this study, two different microstrip designs with varying impedance lines -- one producing peak B1+ in the center and the other extending the length of usable B1+ along the length of the coil-- are investigated. Simulation and image results for 8-channel volume coils incorporating these element designs were obtained using a phantom at 7 tesla.