Whole brain 31 P MRSI at 7T with a dual-tuned receive array

Abstract

Purpose: The design and performance of a novel head coil setup for ${}^{31}$ P spectroscopy at ultra-high field strengths (7T) is presented. The described system supports measurements at both the ${}^1$ H and ${}^{31}$ P resonance frequencies.

Methods: The novel coil consists of 2, actively detunable, coaxial birdcage coils to give homogeneous transmit, combined with a double resonant 30 channel receive array. This allows for anatomical imaging combined with ${}^{31}$ P acquisitions over the whole head, without changing coils or disturbing the subject. A phosphate buffer phantom and 3 healthy volunteers were scanned with a pulse acquire CSI sequence using both the novel array coil and a conventional transceiver birdcage. Four different methods of combining the array channels were compared at 3 different levels of SNR.

Results: The novel coil setup delivers significantly increased ${}^{31}$ P SNR in the peripheral regions of the brain, reaching up to factor 8, while maintaining comparable performance relative to the birdcage in the center.

Conclusions: The new system offers the potential to acquire whole brain ${}^{31}$ P MRSI with superior signal relative to the standard options.

Keywords: ${}^{31}$ P; MRSI; dual-tuned; phosphorus; receive array; spectroscopy.