31P MRSI multi-channel signal combination using 23Na coil sensitivity profiles at 7T: further evaluations in silico, on phantom, and in vivo

Motivation: Multi-channel 31P MRSI signal combination is challenging due to low intrinsic SNR. Goal(s): Improve multi-channel 31P signal combination for a multi-tuned 31P/23Na head coil receiver array. Approach: Combining 15-channel 31P data using the 23Na sensitivity maps received with the same dual-tuned array. The results are evaluated quantitatively and qualitatively in silico, on phantom scans, and in vivo. Results: Simulation shows <5% SNR-decrease by combining 31P signals using 23Na sensitivities. Phantom data shows 25% SNR-decrease but also potential for mitigating point-spreading effect. In vivo data analysis shows 5% SNR increase when the intrinsic SNR is low but 15% decrease after the dataset is denoised. Impact: This study explores an alternative approach for multi-channel 31P MRSI signal combination. The performance is positive when intrinsic SNR is low. This approach can be extended to other X-nuclei with not-too-far Larmor frequencies if multi-tuned receiver antennas are used.