Triple‐tuned birdcage and single‐tuned dipole array for quadri‐nuclear head MRI at 7 T

Abstract

AbstractPurposeThe purpose of this work was to design and build a coil for quadri‐nuclear MRI of the human brain at 7 T.MethodsWe built a transmit/receive triple‐tuned (45.6 MHz for H, 78.6 MHz for Na, and 120.3 MHz for P) quadrature four‐rod birdcage that was geometrically interleaved with a transmit/receive four‐channel dipole array (297.2 MHz for H). The birdcage rods contained passive, two‐pole resonant circuits that emulated capacitors required for single‐tuning at three frequencies. The birdcage assembly also included triple‐tuned matching networks, baluns, and transmit/receive switches. We assessed the performance of the coil with quality factor (Q) and signal‐to‐noise ratio (SNR) measurements, and performed in vivo multinuclear MRI and MR spectroscopic imaging (MRSI).ResultsQ measurements showed that the triple‐tuned birdcage efficiency was within 33% of that of single‐tuned baseline birdcages at all three frequencies. The quadri‐tuned coil SNR was 78%, 59%, 44%, and 48% lower than that of single or dual‐tuned reference coils for H, H, Na, and P, respectively. Quadri‐nuclear MRI and MRSI was demonstrated in brain in vivo in about 30 min.ConclusionWhile the SNR of the quadruple tuned coil was significantly lower than dual‐ and single‐tuned reference coils, it represents a step toward truly simultaneous quadri‐nuclear measurements.