Double-frequency birdcage volume coils for 4.7T and 7T

The aim of this study was to find an optimum design for a volume RF coil for large rodent MRI/MRS at 4.7T and 7T. Three double-frequency birdcage-type coils were made and compared with single-frequency coils. The most efficient design was a birdcage coil with alternate tuned elements. This coil retains most of the sensitivity of a single-tuned coil while preserving B, homogeneity. Spiral and four-ring coils suffer lower efficiency at one of two frequencies. Tests of the 7T coil demonstrated high-quality proton images and phosphorous spectra of a woodchuck liver. (c) 2005 Wiley Periodicals, Inc.