ABSTRACT
This chapter introduces the concepts of resonance and reciprocity to illustrate the basic requirements of radiofrequency (RF) coils. It describes a simple analysis of RF coils, which models an RF coil with an equivalent lumped-circuit. RF serves two purposes: The first is to generate RF pulses at the Larmor frequency to excite the nuclei in the object to be imaged. The second is to pick up RF signals emitted by the nuclei at the same frequency. The second is to pick up RF signals emitted by the nuclei at the same frequency. An RF shield made of an RF opaque or mesh screen can provide effective decoupling between the RF coil and the gradient and shim coils provided that the screen has a thickness of several RF skin-depths. As mentioned earlier, the equivalent circuit method is an approximate analysis. It is applicable to RF coils whose size is a small fraction of the RF wavelength.
