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

PURPOSE

To develop a robust design of a human head double-tuned P/ H array, which provides good performance at both P and 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 H and P frequency. To minimize this effect, we limited the number of elements in the P array to 10, i.e., 8 transceiver surface loops circumscribing the head and 2 receive "vertical" loops placed at the superior location. The 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 P array and 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 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 P/ H double-tuned array for MR spectroscopic imaging of a human brain at 9.4T. Placing both P and H loops in a single layer provides for high transmit efficiency at both frequencies without compromising SNR near the brain center at the P-frequency. Addition of the cross-loops at the superior location improves the brain coverage.