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Comparison of four 31P single‐voxel MRS sequences in the human brain at 9.4 T
Author(s) -
Dorst Johanna,
Ruhm Loreen,
Avdievich Nikolai,
Bogner Wolfgang,
Henning Anke
Publication year - 2021
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.28658
Subject(s) - imaging phantom , voxel , nuclear magnetic resonance , in vivo , in vivo magnetic resonance spectroscopy , physics , flip angle , scanner , chemistry , magnetic resonance imaging , optics , computer science , artificial intelligence , biology , medicine , microbiology and biotechnology , radiology
Purpose In this study, different single‐voxel localization sequences were implemented and systematically compared for the first time for phosphorous MRS ( 31 P‐MRS) in the human brain at 9.4 T. Methods Two multishot sequences, image‐selected in vivo spectroscopy (ISIS) and a conventional slice‐selective excitation combined with localization by adiabatic selective refocusing (semiLASER) variant of the spin‐echo full intensity–acquired localized spectroscopy (SPECIAL‐semiLASER), and two single‐shot sequences, semiLASER and stimulated echo acquisition mode (STEAM), were implemented and optimized for 31 P‐MRS in the human brain at 9.4 T. Pulses and coil setup were optimized, localization accuracy was tested in phantom experiments, and absolute SNR of the sequences was compared in vivo. The SNR per unit time (SNR/t) was derived and compared for all four sequences and verified experimentally for ISIS in two different voxel sizes (3 × 3 × 3 cm 3 , 5 × 5 × 5 cm 3 , 10‐minute measurement time). Metabolite signals obtained with ISIS were quantified. The possible spectral quality in vivo acquired in clinically feasible time (3:30 minutes, 3 × 3 × 3 cm 3 ) was explored for two different coil setups. Results All evaluated sequences performed with good localization accuracy in phantom experiments and provided well‐resolved spectra in vivo. However, ISIS has the lowest chemical shift displacement error, the best localization accuracy, the highest SNR/t for most metabolites, provides metabolite concentrations comparable to literature values, and is the only one of the sequences that allows for the detection of the whole 31 P spectrum, including β–adenosine triphosphate, with the used setup. The SNR/t of STEAM is comparable to the SNR/t of ISIS. The semiLASER and SPECIAL‐semiLASER sequences provide good results for metabolites with long T 2 . Conclusion At 9.4 T, high‐quality single‐voxel localized 31 P‐MRS can be performed in the human brain with different localization methods, each with inherent characteristics suitable for different research issues.