Heteronuclear multivoxel spectroscopy of in vivo human brain: two-dimensional proton interleaved with three-dimensional 1H-decoupled phosphorus chemical shift imaging.

Multivoxel, heteronuclear interleaved two-dimensional proton and three-dimensional 1H-decoupled 31P CSI of human brain is demonstrated. This method offers efficient use of limited examination time as patient preparation, coil tuning, shimming and imaging are done only once and the CSI data sets from both nuclei are obtained concurrently. Effective interleaving of 31P and 1H is possible due to the shorter T1s of proton brain metabolites, allowing a 1H acquisition cycle to be inserted into each 31P TR. This way, the entire MRS time is available to both nuclei, increasing their SNR per-unit-time by approximately 12% for 31P and approximately 80% for 1H, compared with sequential detection of equal (45-50 min) length. The spectral resolution and SNR of 31P are further increased through bi-level 1H-decoupling and NOE.