Tissue-equivalent phantoms for high frequencies

Saline phantoms have been used traditionally as biological mimics to load radio frequency (RF) coils during development and testing. However, the relative permittivity of biological tissues diverges from that of water as frequencies increase, resulting in saline phantoms loading coils much differently than the real biological systems. We have developed tissue-equivalent phantoms with compartments containing gels that approach the relative permittivities and conductivities of a rat at 470 MHz. The gel characteristics are measured with a coaxial probe and the coil-loading characteristics of the assembled phantoms are compared with real animals. It is shown that the tissue-equivalent phantoms load coils similarly to live rats, unlike the saline phantoms. Using these tissue-equivalent phantoms, the coil designer can be confident that when the coil leaves the laboratory to be used in the magnet, it will be optimized for the biological system of interest. (C) 2004 Wiley Periodicals, Inc.