A simple approach towards a multi-frequency MRI head phantom

An anatomically realistic human head phantom was elaborated for different Larmor frequencies, which allows rapid quantification of B
₁
⁺
of MRIs of different magnetic fields. The permittivity ε' and conductivity σ of sucrose/salt/agar aqueous solutions of varying concentration was determined; a solution with these components and having the adequate concentration to obtain the brain's dielectric properties at 3 T, 7T and 11.7T was manufactured. An anthropomorphic polymeric skull was filled with this mixture. To check the behavior of this phantom in a MRI configuration, both numerical and experimental validations were done: a B
₁
+ field distribution inside the phantom was calculated with CST Microwave Studio inside a birdcage coil at 7T; the same mapping was assessed in a 7T MRI. This work has shown the possibility of manufacturing a head phantom with accessible and cheap components for MRI evaluation, having an adequate B
₁
⁺
field distribution and the dielectric properties of the human brain at several frequencies of interest.