Ultimate signal-to-noise-ratio of surface and body antennas for magnetic resonance imaging

Approximating the human body by a homogeneous half-space or cylinder the electromagnetic fields of surface antennas or wholebody antennas for magnetic resonance imaging (MRI) can analytically be calculated. Using these expressions the signal-to-noise ratio (SNR) of a general magnetic resonance detecting antenna can be predicted. We show how the optimum magnetic resonance antenna must look like to achieve the maximum SNR, which is also presented. Finally, we apply the derived formulas to special antenna geometries like the single- and the double-loop coil, the magnetic dipole, and the "birdcage" resonator.