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

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.

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.

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.

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.