A simple method for mapping the B1 field distribution of linear RF coils.

Inhomogeneity of the radio frequency (RF) field B1 leads to intensity variations in MR images and to spatial dependence of spectral line amplitudes. In this paper, a simple method of measuring the B1 field components of an unsegmented linear coil is described. The method is designed for the coils operating up to 20 MHz. The B1 field distribution is replaced by the static magnetic field caused by DC current flowing through the coil. The technique involves rotating the coil 90 degrees so that measured B1 component is aligned with B0 and measuring the shift of resonance frequency using a spectroscopic imaging sequence. Experimental results were in good agreement with the theoretical computations.