A theoretical and experimental study on transverse field radio frequency surface coils

We have analysed, theoretically and experimentally, transverse field RF surface coils comprising two parallel linear current elements (figure-of-eight, FO8). A quasi-static numerical integration of the Biot–Savart law was used to simulate the B1 field distribution of FO8 coils comprising a range of coil diameters and linear element separations. RF coil prototypes, suitable for 1H and 31P magnetic resonance imaging/spectroscopy at 1.5 T, that closely match the simulated models, were built and tested using workbench and MRI methods. A comparison with standard loop RF coils was made. Testing with phantoms showed a good agreement between the theoretical and experimental RF field distributions. Our findings should be useful to optimize the sensitivity and spatial selectivity of FO8 coils by a careful choice of the geometrical parameters. A number of applications where the use of FO8 RF coils could be of benefit are discussed, these include in vivo nuclear magnetic resonance imaging/spectroscopy.