A design for a double-tuned birdcage coil for use in an integrated MRI/MRS examination

The performance of a new design for a double-tuned birdcage volume coil using multiple-pole tuning elements was evaluated. The relative signal to noise of a double-tuned four-strut extremity coil (22 cm long, 15 cm diameter) was compared with that of two single-tuned extremity coils of the same dimensions. The signal to noise of the double-tuned extremity coil at the ¹H frequency was 92 ± 3% of that obtained with the single-tuned proton coil. The signal-to-noise ratio obtained with the double-tuned coil at the ³¹P frequency was 94 ± 4% of the signal to noise obtained with the single-tuned ³¹P Coil. The signal-to-noise comparisons between the extremity coils show that the double-tuned design is competitive with single-tuned coils of similar design at both frequencies and may actually make possible images and spectra with superior signal to noise to that obtainable with single-tuned coils in an integrated exam. These preliminary experiments show that this new design has advantages over single-tuned coils for generating spatially localized ³¹P spectra. This dual capability offers clear advantages for the integration of MRI and MRS in the clinical setting.