An 8-channel receive array for improved 31 P MRSI of the whole brain at 3T

Abstract

Purpose: To demonstrate a ¹ H/³¹ P whole human brain volume coil configuration for 3 Tesla with separate ³¹ P transmit and receive components that maintains ¹ H MRS performance and delivers optimal ³¹ P MRSI with ¹ H decoupling.

Methods: We developed an 8-channel ³¹ P receive array coil covering the head to be used as an insert for a commercial double-tuned ¹ H/³¹ P birdcage transmit-receive coil. This retains the possibility of using low-power rectangular pulses for ¹ H-decoupled 3D ³¹ P MRSI (nominal resolution 17.6 cm³ ; acquisition duration 13 min) but increases the SNR with the receive sensitivity of ³¹ P surface coils. The performance of the combined coil setup was evaluated by measuring ¹ H and ³¹ P SNR with and without the ³¹ P receive array and by assessing the effect of the receive array on the transmit efficiencies of the birdcage coil.

Results: Compared to the birdcage coil alone, the ³¹ P insert in combination with the birdcage achieved an average ³¹ P SNR gain of 1.4 ± 0.4 in a center partition of the brain. The insert did not cause losses in ¹ H MRS performance and transmit efficiency, whereas for ³¹ P approximately 20% more power was needed to achieve the same γB1.

Conclusion: The new coil configuration allows ¹ H MRSI and optimal ¹ H-decoupled 3D ³¹ P MRSI, with increased SNR of the human brain without patient repositioning, for clinical and research purposes at 3 Tesla.

Keywords: 1H-decoupling; 3 Tesla; 31P MR spectroscopic imaging; RF array coil; brain.