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Water suppression in the human brain with hypergeometric RF pulses for single‐voxel and multi‐voxel MR spectroscopy
Author(s) -
Chan Kimberly L.,
Ouwerkerk Ronald,
Barker Peter B.
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.27133
Subject(s) - voxel , residual , water vapor , nuclear magnetic resonance , spectroscopy , chemistry , physics , mathematics , radiology , medicine , algorithm , organic chemistry , quantum mechanics
Purpose To develop and investigate a novel water suppression sequence with hypergeometric pulses at 3 T. Methods Simulations were used to optimize the delays and amplitudes of 5 hypergeometric prepulses, to minimize the residual water over a range of T 1 and B 1 values. Single‐voxel data with hypergeometric water suppression (HGWS) prepulses were acquired in the centrum semiovale, 2 parietal regions, and insula of 7 subjects, and compared with VAPOR water suppression. Magnetic resonance spectroscopic imaging (MRSI) data using both VAPOR and HGWS prepulses were also collected and compared. Water suppression performance was calculated as the residual water peak height relative to the unsuppressed water peak. MRSI voxel‐by‐voxel comparison was performed by calculating the ratio between HGWS and VAPOR residual water peaks. Results In simulations, HGWS and VAPOR are insensitive to B 1 and water T 1 variations, but with no B 1 variation, HGWS has a lower average residual water fraction (0.0033) than that of VAPOR (0.0091). In single‐voxel acquisitions, HGWS performs better than VAPOR in all regions with a 2.3‐fold to 5.7‐fold lower residual water. In MRSI acquisitions, HGWS performs on average 2.3‐fold better than VAPOR in 98.9% of the voxels. Conclusion HGWS provides better water suppression than VAPOR in both single‐voxel and multivoxel acquisitions with a shorter sequence duration.