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Accurate flip‐angle calibration for 13 C MRI
Author(s) -
Hancu Ileana,
Watkins Ronald,
Kohler Susan J.,
Mallozzi Richard P.
Publication year - 2007
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.21252
Subject(s) - calibration , flip angle , signal (programming language) , artifact (error) , nuclear magnetic resonance , in vivo , noise (video) , electromagnetic coil , signal to noise ratio (imaging) , computer science , physics , materials science , nuclear medicine , magnetic resonance imaging , optics , artificial intelligence , radiology , medicine , image (mathematics) , quantum mechanics , programming language , microbiology and biotechnology , biology
13 C imaging and spectroscopy in the presence of injected labeled compounds can vastly extend the capability of MRI to perform metabolic imaging. The details of imaging in the presence of injected compounds, however, pose new technological challenges. Pulse sequences, in general, rely on precise flip‐angle (FA) calibration to create high signal‐to‐noise ratio (SNR), artifact‐free images. Signal quantification also requires precise knowledge of the excitation FA. In MRI scans that rely on signal acquisitions from injected compounds, however, such FA calibration is challenged by low natural‐abundance 13 C signal levels before injection, and by time‐varying signal following injection. A method to precisely set the FA at the 13 C frequency based on FA calibration at the 23 Na frequency is presented here. A practical implementation of a coil (a dual‐tuned, 23 Na/ 13 C low‐pass birdcage coil) suitable for this calibration in vivo is also documented. Accurate FA calibration is demonstrated at the 13 C frequency for in vivo rat experiments using this approach. Magn Reson Med 58:128–133, 2007. © 2007 Wiley‐Liss, Inc.