Improved off-resonance phase behavior using a phase-inverted adiabatic half-passage pulse for <sup>13</sup> C MRS in humans at 7 T.

Details

Serval ID
serval:BIB_EBECFB67D271
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Improved off-resonance phase behavior using a phase-inverted adiabatic half-passage pulse for <sup>13</sup> C MRS in humans at 7 T.
Journal
NMR in biomedicine
Author(s)
Serés Roig E., Xin L., Gallichan D., Mlynarik V., Gruetter R.
ISSN
1099-1492 (Electronic)
ISSN-L
0952-3480
Publication state
Published
Issued date
12/2019
Peer-reviewed
Oui
Volume
32
Number
12
Pages
e4171
Language
english
Notes
Publication types: Journal Article ; Research Support, Non-U.S. Gov't
Publication Status: ppublish
Abstract
In vivo <sup>13</sup> C MRS at high field benefits from an improved SNR and spectral resolution especially when using surface coils in combination with adiabatic pulses, such as the adiabatic half-passage (AHP) pulse for <sup>13</sup> C excitation. However, the excitation profile of the AHP pulse is asymmetric relative to the carrier frequency, which could lead to asymmetric excitation of the spectral lines relative to the center of the spectrum. In this study, a pulse-acquire sequence was designed for adiabatic <sup>13</sup> C excitation with a symmetric bandwidth, utilizing a combination of two AHP pulses with inverted phases in alternate scans. Magnetization and phase behavior as a function of frequency offset and RF amplitude of the B <sub>1</sub> field, as well as the steady-state transverse magnetization response to off-resonance, were simulated. Excitation properties of the combined pulse sequence were studied by <sup>23</sup> Na imaging and <sup>13</sup> C spectroscopy in vitro on a phantom and in vivo on the human calf at 7 T. Simulations demonstrated symmetric transverse magnetization and phase with respect to positive and negative frequency offsets when using two AHP pulses with inverted phases in alternate scans, thereby minimizing baseline distortion and achieving symmetric T <sub>1</sub> weighting, as confirmed by in vitro measurements. The intensities of the lipid peaks at 15, 30, 62, 73, and 130 ppm were in agreement with those theoretically predicted using two AHP pulses with inverted phases in alternate scans. We conclude that using two phase-inverted AHP pulses improves the symmetry of the <sup>13</sup> C excitation profile and phase response to off-resonance effects at 7 T in comparison with using a single AHP pulse.
Keywords
Carbon-13 Magnetic Resonance Spectroscopy, Computer Simulation, Humans, Male, Muscles/diagnostic imaging, Protons, Sodium/chemistry, 13C excitation bandwidth, 13C nucleus, adiabatic half-passage (AHP), human calf at 7 T, natural abundance 13C resonances, off-resonance
Pubmed
Web of science
Funding(s)
CHUV
Create date
20/09/2019 23:18
Last modification date
23/04/2024 6:59
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