Purpose:To develop a robust design of a human head double-tuned 31 P/ 1 H array, which provides good performance at both 31 P and 1 H frequencies for MR spectroscopic imaging at 9.4T. Methods: Increasing the number of surface loops in a human head array improves the peripheral signal-to-noise ratio (SNR), while the central SNR doesn't substantially change. High peripheral SNR can contaminate MR spectroscopic imaging data at both 1 H and 31 P frequency. To minimize this effect, we limited the number of elements in the 31 P array to 10, i.e., 8 transceiver surface loops circumscribing the head and 2 receive "vertical" loops placed at the superior location. The 1 H-portion of the array also consists of 10 elements, i.e., 8 transceiver surface loops circumscribing the head and 2 transceiver "vertical" loops at the superior location of the head. Both the 31 P array and 1 H array are placed in a single layer at the same distance to the head, which provides high loading and, thus, a good performance for both arrays. Results: Transmit efficiency of the 1 H-portion of the double-tuned array was very similar to that of the single-tuned arrays of similar size. Also, addition of the crossloops substantially improved the brain coverage. Conclusion: We developed a novel 31 P/ 1 H double-tuned array for MR spectroscopic imaging of a human brain at 9.4T. Placing both 31 P and 1 H loops in a single layer provides for high transmit efficiency at both frequencies without compromising SNR near the brain center at the 31 P-frequency. Addition of the cross-loops at the superior location improves the brain coverage.

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Purpose To present 31P whole brain MRSI with a high spatial resolution to probe quantitative tissue analysis of 31P MRSI at an ultrahigh field strength of 9.4 Tesla. Methods The study protocol included a 31P MRSI measurement with an effective resolution of 2.47 mL. For SNR optimization, the nuclear Overhauser enhancement at 9.4 Tesla was investigated. A sensitivity correction was achieved by applying a low rank approximation of the γ‐adenosine triphosphate signal. Group analysis and regression on individual volunteers were performed to investigate quantitative concentration differences between different tissue types. Results Differences in gray and white matter tissue 31P concentrations could be investigated for 12 different 31P resonances. In addition, the first highly resolved quantitative MRSI images measured at B0 = 9.4 Tesla of 31P detectable metabolites with high SNR could be presented. Conclusion With an ultrahigh field strength B0 = 9.4 Tesla, 31P MRSI moves further toward quantitative metabolic imaging, and subtle differences in concentrations between different tissue types can be detected.