Image uniformity improvement for birdcage-like volume coils at 400 MHz using multichannel excitations

We present a new method to deal with MRI non‐uniformities caused by electromagnetic wave interference patterns at 300–400 MHz in lossy dielectrics. The non‐uniformities are also known as “dielectric resonance” effects, yielding bright and dark spots at higher frequencies. The proposed method consists of applying a series of multiple cos(nϕ) (n = 1, …) circular current distributions on the birdcage legs in independent MRI experiments. The signals obtained during each experiment are then coalesced into a uniform image using appropriate weighting factors. The level of uniformity is improved by the application of additional cos(nϕ)‐birdcage‐like channels. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 29B: 153–160, 2006