Cardiac Metabolism Research Group, Department of Physiology, Anatomy & Genetics, Sherrington Building, University of Oxford, Oxford, UK.
Magn Reson Med. 2010 Oct;64(4):957-66. doi: 10.1002/mrm.22511.
Use of a repetition time similar to, or shorter than, metabolite T(1)s is common in NMR spectroscopy of biological samples to improve the signal-to-noise ratio. Conventionally, the partial saturation that results from this is corrected using saturation factors. However, this can lead to erroneous results in the presence of chemical exchange or nonconstant T(1)s. We describe an alternative approach to correction for saturation, based on ongoing dual-angle T(1) measurement. Using (31)P magnetic resonance spectroscopy of the perfused rat heart undergoing ischemia-reperfusion, we demonstrate that signal alternations in the data acquired by the dual-angle approach are eliminated by the ongoing dual-angle T(1) measurement correction scheme, meaning that metabolite concentration and T(1) measurement can be made throughout the course of the ischemia-reperfusion protocol. Simulations, based on parameters pertinent to the perfused rat heart, demonstrate that accurate saturation correction is possible with this method except at times of rapid concentration change. Additionally, compared to the conventional saturation factor correction method, the ongoing dual-angle T(1) measurement correction scheme results in improved accuracy in determining the [phosphocreatine] recovery time constant. Thus, the ongoing dual-angle T(1) measurements procedure permits accurate monitoring of metabolite concentrations even in the setting of chemical exchange and T(1) changes and allows more accurate analysis of bioenergetic status.
在对生物样本的 NMR 光谱进行分析时，通常使用与代谢物 T1 相似或更短的重复时间来提高信噪比。传统上，通过使用饱和因子来校正由此产生的部分饱和。然而，在存在化学交换或 T1 非恒定时，这可能会导致错误的结果。我们描述了一种替代的饱和校正方法，该方法基于持续的双角度 T1 测量。使用经历缺血再灌注的灌注大鼠心脏的 31P 磁共振波谱，我们证明通过双角度方法获得的数据中的信号交替可以通过持续的双角度 T1 测量校正方案消除，这意味着可以在整个缺血再灌注方案中进行代谢物浓度和 T1 测量。基于与灌注大鼠心脏相关的参数的模拟表明，该方法除了在浓度快速变化的情况下外，都可以进行准确的饱和校正。此外，与传统的饱和因子校正方法相比，持续的双角度 T1 测量校正方案在确定[磷酸肌酸]恢复时间常数方面具有更高的准确性。因此，持续的双角度 T1 测量过程即使在存在化学交换和 T1 变化的情况下也允许对代谢物浓度进行准确监测，并允许更准确地分析生物能量状态。
