Fast and accurate 31P B1-mapping at high magnetic fields with short TRs.

Motivation: Fast and accurate B1 mapping for 31P MRI is challenging due to the low sensitivity of 31P nucleus and its long T1 relaxation times. Goal(s): This study aims to develop a fast B1 mapping approach for 31P at 7T. Approach: A look-up table approach was adopted to enable B1 mapping at short TR. Fast spiral encoding together with weighted averaging was implemented with a GRE sequence to further accelerate the acquisition. Results: B1 mapping was validated in phantom and in vivo in human calf muscle and brain within a scan time of 10min. Impact: The presented fast and accurate B1 mapping correction method is particularly suited for moderate to short repetition times, showing promise for future applications in rapid X-nuclei imaging.