Christopher P. Bidinosti1, Chen-Yi Liu1, Scott B. King2
Spiral birdcage coils have been used for transmit array spatial encoding (TRASE) as well as for partially correcting central image brightening. A Fourier transform method usually employed for designing wire-wound shim, gradient and low frequency RF coils is used here to analyze the magnetic field symmetries of the spiral birdcage coil. Results show that twisting leads to a strong, intrinsic radial dependence in all magnetic field components. This knowledge will guide the optimization of coils used for TRASE, and may also lead to a more direct correction scheme for the problem of central brightening that occurs in high field MRI.