3D virtual biopsy of in vivo pH and metabolism using semi-LASER MRS of hyperpolarized 13C nuclei

Motivation: Hyperpolarized 13C magnetic resonance enables the detection of metabolism and pH using [1-13C]pyruvate or [1,5-13C2]Z-OMPD respectively. There is still a need for magnetization-efficient sequences with high spectral resolution and achieving large volume coverage. Goal(s): To improve upon previously reported multi-voxel PRESS by implementing semi-LASER using adiabatic refocusing pulses, enabling localized MRS with 3D voxel placement. Approach: A custom semi-LASER sequence was implemented and compared to PRESS in 1H phantoms and in animals using two hyperpolarized molecules. Results: Semi-LASER enables dynamic localized MRS in mouse kidneys as well as pH measurements in more voxels and with a higher SNR than PRESS. Impact: We show for the first time the use of adiabatic refocusing pulses for hyperpolarized 13C multi-voxel MRS to detect pH and metabolism, with high spectral resolution and short acquisition time, while maintaining high spatial customizability.