Theoretical description of the interaction between birdcage coils and lossy samples.

An analysis is presented of the interaction between a long cylindrical imaging coil, commonly called a low-pass birdcage coil, and a cylindrical sample. Predicted and measured values of coil Q are shown to compare well throughout the resonance spectrum of an experimental coil-sample system. The analysis may be used to calculate feed-point impedances and is easily extended to high-pass coils.