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首页> 外文期刊>Applied Magnetic Resonance >Discrete and Continuous Spin-Spin Relaxation Rate Distributions Derived from CPMG NMR Response Curves: a Comparative Analysis Exemplified by Water in Meat
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Discrete and Continuous Spin-Spin Relaxation Rate Distributions Derived from CPMG NMR Response Curves: a Comparative Analysis Exemplified by Water in Meat

机译：从CPMG NMR响应曲线得出的离散和连续自旋-自旋弛豫速率分布：肉中水举例说明的比较分析

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摘要

The spin-spin relaxation rate distribution of water in a porcine longissimus dorsi muscle was derived from an inverse integral transformation of the proton CPMG (Carr-Purcell-Meiboom-Gill) NMR (nuclear magnetic resonance) signal at each hour during a 49 h drip period. This "continuous (C)" relaxation rate distribution was found to be excellently represented by an empirical peak function, characterized by three parameters: a peak width, an average relaxation rate, and a skewness parameter, which enable the distribution to be quantitatively defined. In addition, the same CPMG response was fitted to a sum of three single-exponential decay functions, denoted a "discrete (D)" relaxation rate model. The analysis shows that when the fraction of the slow relaxation component from the continuous model is close to 5 %, which is a rather typical value, the mean relaxation rate from the discrete model becomes larger than the corresponding relaxation rate from the continuous model by nearly 25 % and becomes larger than by more than 75 %. Likewise, when approaches 2.5 %, becomes larger than by more than 75 % and becomes larger than by more than a factor of 3 which are supported by model simulations. The relative quality and goodness of the two different relaxation rate models are discussed. Finally, the number of transients needed to obtain a preset error in relaxation rate and/or mole fraction was determined by model simulation.
机译：猪背最长肌中水的自旋自旋弛豫速率分布是由49 h滴水过程中每小时每小时质子CPMG（Carr-Purcell-Meiboom-Gill）NMR（核磁共振）信号的逆积分变换得出的期。发现该“连续（C）”弛豫率分布由经验峰函数很好地表示，该经验峰函数的特征在于三个参数：峰宽，平均弛豫率和偏度参数，这使得可以定量定义分布。此外，将相同的CPMG响应拟合到三个单指数衰减函数的总和，表示为“离散（D）”松弛率模型。分析表明，当连续模型中的慢弛豫分量的比例接近5％（这是一个非常典型的值）时，离散模型的平均弛豫率将比连续模型中的相应弛豫率大近25％，大于75％。同样，当逼近2.5％时，模型仿真支持的比例大于75％，大于3的比例。讨论了两种不同松弛率模型的相对质量和优度。最后，通过模型仿真来确定获得松弛率和/或摩尔分数的预设误差所需的瞬变次数。

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