Ren Jimin, Sherry A Dean, Malloy Craig R
Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Magn Reson Med. 2015 Dec;74(6):1505-14. doi: 10.1002/mrm.25514. Epub 2014 Dec 2.
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.
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.
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.
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.
本研究的目的是增强γ-三磷酸腺苷（ATP）与无机磷酸（Pi）之间的磁化交换效应，以评估人体骨骼肌中的ATP合成速率。
该策略的工作原理是使用宽带绝热反转射频脉冲同时反转磷酸肌酸（PCr）和ATP的（31）P共振，然后观察未反转的Pi信号强度相对于反转脉冲与观察脉冲之间延迟时间的动态变化。这种带反转技术显著延迟了γ-ATP磁化的恢复；因此，很容易检测和分析交换反应Pi↔γ-ATP。
使用该方法从高质量光谱数据测得的静息人体骨骼肌中的ATP合成速率为0.073±0.011 s⁻¹（N = 10）。Pi的T1为6.93±1.90 s，与该场强下Pi的固有T1一致。γ-ATP的表观T1为4.07±0.32 s，由于PCr中磁化的存储，比其固有T1长约两倍。
带反转提供了一种有效方法来增强γ-ATP与Pi之间的磁化转移效应。使用两点交换模型可以轻松分析所得数据以获得ATP合成速率。
