Double-tuned four-ring birdcage resonators forin vivo 31P-nuclear magnetic resonance spectroscopy at 11.75 T

A high signal-to-noise ratio (SNR) in³¹P-nuclear magnetic resonance (³¹P-NMR) spectroscopy can be obtained only with goodB ₀-field homogeneity and optimal coil sensitivity. This demands double-tumed coils with a highly sensitive³¹P channel and an additional¹H channel for¹H-magnetic resonance imaging, shimming,¹H decoupling, and nuclear Overhauser enhancement (NOE). For studies on an 11.75 T magnet, we built coils derived from the four-ring birdcage design originally described by Murphy-Boesch. A comparison with conventional, single-tuned coils shows that, in spite of double tuning, there is no significant loss in³¹P sensitivity while the¹H channel provides the requested performance. The coil design offers the advantage of circular polarization on both channels. Supported by the Deutsche Forschungsgemeinschaft (Ki 433/2-2 and Graduiertenkolleg Ha 1232/8-2).