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. 2020 Aug;84(2):1076-1089.
doi: 10.1002/mrm.28176. Epub 2020 Jan 30.

Double-tuned 31 P/1 H human head array with high performance at both frequencies for spectroscopic imaging at 9.4T

Nikolai I Avdievich  1 , Loreen Ruhm  1 , Johanna Dorst  1 , Klaus Scheffler  1   2 , Andreas Korzowski  3 , Anke Henning  1   4
Affiliations

Double-tuned 31 P/1 H human head array with high performance at both frequencies for spectroscopic imaging at 9.4T

Nikolai I Avdievich et al. Magn Reson Med. 2020 Aug.

Abstract

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 cross-loops 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.

Keywords: MRSI; RF human head coil; central SNR; double-tuned arrays; ultra-high field MRI.

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References

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