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Amplification of the effects of magnetization exchange by 31 P band inversion for measuring adenosine triphosphate synthesis rates in human skeletal muscle
Author(s) -
Ren Jimin,
Sherry A. Dean,
Malloy Craig R.
Publication year - 2015
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.25514
Subject(s) - magnetization , pi , adenosine triphosphate , phosphocreatine , magnetization transfer , chemistry , nuclear magnetic resonance , skeletal muscle , biophysics , physics , magnetic field , biochemistry , biology , anatomy , medicine , quantum mechanics , energy metabolism , magnetic resonance imaging , radiology , endocrinology
Purpose The goal of this study was to amplify the effects of magnetization exchange between γ‐adenosine triphosphate (ATP) and inorganic phosphate (Pi) for evaluation of ATP synthesis rates in human skeletal muscle. Methods The strategy works by simultaneously inverting the 31 P resonances of phosphocreatine (PCr) and ATP using a wide bandwidth, adiabatic inversion radiofrequency pulse followed by observing dynamic changes in intensity of the noninverted Pi signal versus the delay time between the inversion and observation pulses. This band inversion technique significantly delays recovery of γ‐ATP magnetization; consequently, the exchange reaction, Pi ↔ γ‐ATP , is readily detected and easily analyzed. Results The ATP synthesis rate measured from high‐quality spectral data using this method was 0.073 ± 0.011 s −1 in resting human skeletal muscle (N = 10). The T 1 of Pi was 6.93 ± 1.90 s, consistent with the intrinsic T 1 of Pi at this field. The apparent T 1 of γ‐ATP was 4.07 ± 0.32 s, about two‐fold longer than its intrinsic T 1 due to storage of magnetization in PCr. Conclusion Band inversion provides an effective method to amplify the effects of magnetization transfer between γ‐ATP and Pi. The resulting data can be easily analyzed to obtain the ATP synthesis rate using a two‐site exchange model. Magn Reson Med 74:1505–1514, 2015. © 2014 Wiley Periodicals, Inc.