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Establishing an accurate gas phase reference frequency to quantify 129 Xe chemical shifts in vivo
Author(s) -
Virgincar Rohan S.,
Robertson Scott H.,
Nouls John,
Degan Simone,
Schrank Geoffry M.,
He Mu,
Driehuys Bastiaan
Publication year - 2017
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.26229
Subject(s) - gas phase , phase (matter) , in vivo , chemistry , nuclear magnetic resonance , analytical chemistry (journal) , physics , environmental chemistry , biology , microbiology and biotechnology , organic chemistry
Purpose 129 Xe interacts with biological media to exhibit chemical shifts exceeding 200 ppm that report on physiology and pathology. Extracting this functional information requires shifts to be measured precisely. Historically, shifts have been reported relative to the gas‐phase resonance originating from pulmonary airspaces. However, this frequency is not fixed—it is affected by bulk magnetic susceptibility, as well as Xe–N 2 , Xe–Xe, and Xe–O 2 interactions. In this study, we addressed this by introducing a robust method to determine the 0 ppm 129 Xe reference from in vivo data. Methods Respiratory‐gated hyperpolarized 129 Xe spectra from the gas‐ and dissolved‐phases were acquired in four mice at 2T from multiple axial slices within the thoracic cavity. Complex spectra were then fitted in the time domain to identify peaks. Results Gas‐phase 129 Xe exhibited two distinct resonances corresponding to 129 Xe in conducting airways (varying from −0.6 ± 0.2 to 1.3 ± 0.3 ppm) and alveoli (relatively stable, at −2.2 ± 0.1 ppm). Dissolved‐phase 129 Xe exhibited five reproducible resonances in the thorax at 198.4 ± 0.4, 195.5 ± 0.4, 193.9 ± 0.2, 191.3 ± 0.2, and 190.7 ± 0.3 ppm. Conclusion The alveolar 129 Xe resonance exhibits a stable frequency across all mice. Therefore, it can provide a reliable in vivo reference frequency by which to characterize other spectroscopic shifts. Magn Reson Med 77:1438–1445, 2017. © 2016 International Society for Magnetic Resonance in Medicine