ABSTRACT:A simple 2-D full wave model for the birdcage coil is described that includes the effects of shields, lossy layered media, and finite leg widths. This model has been implemented in Matlab, which provides a simple user interface. Using this model, various coil parameters such as signal-to-noise ratio (SNR), magnetic field homogeneity, magnetic field magnitude, etc. can be computed quickly. The efficiency of this model allows optimization of the coil geometry for particular applications. A method for finding the optimal coil radius in terms of SNR and homogeneity, given shield and sample radii, is presented.

Different array topologies are examined and compared in an effort to improve arrays for MRI and for SENSE imaging. The prerequisites for a good array are high intrinsic signal-to-noise ratio (SNR) and low noise amplification (g-factor) during SENSE acquisitions. The merits of two classes of planar arrays are discussed-arrays composed of small elements with ''local'' sensitivity versus arrays made up of elements that have a ''global'' sensitivity over the entire field of view.

Large arrays of RF coils with 16 or more channels are becoming commercially available. However, most MR scanners have eight or fewer receiver channels. In order for these scanners to achieve the SNR benefits of these large arrays, the signals from the array elements must be combined. In this paper, strategies for combining the array elements into 8 or fewer channels are discussed and an analysis of the expected SNR improvement is presented. We expect these results to scale to cases such as 32 channels with 128 array elements.