Jimin Ren1,2, A Dean Sherry1,2,3, Craig R Malloy1,2,4,5. 1. Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA. 2. Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA. 3. Department of Chemistry, University of Texas at Dallas, Richardson, Texas, USA. 4. Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA. 5. VA North Texas Health Care System, Dallas, Texas, USA.
Abstract
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 T1 of Pi was 6.93 ± 1.90 s, consistent with the intrinsic T1 of Pi at this field. The apparent T1 of γ-ATP was 4.07 ± 0.32 s, about two-fold longer than its intrinsic T1 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.
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 T1 of Pi was 6.93 ± 1.90 s, consistent with the intrinsic T1 of Pi at this field. The apparent T1 of γ-ATP was 4.07 ± 0.32 s, about two-fold longer than its intrinsic T1 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.
Authors: Ladislav Valkovič; Marek Chmelík; Ivica Just Kukurova; Martin Krššák; Stephan Gruber; Ivan Frollo; Siegfried Trattnig; Wolfgang Bogner Journal: Eur J Radiol Date: 2011-12-10 Impact factor: 3.528
Authors: Chen Chen; Mary C Stephenson; Andrew Peters; Peter G Morris; Susan T Francis; Penny A Gowland Journal: Magn Reson Med Date: 2017-03-16 Impact factor: 4.668