Estimation of relaxation time distribution for NMR CPMG measurements

[摘要] We use a MARAN-2 laboratory NMR spectrometer for making measurements using the CPMG pulse sequence for estimating the spin-spin or T$sb2$ relaxation time distribution. Algorithms are developed for estimating the relaxation time distribution. Guidelines are given for designing the measurements to reduce measurement artifacts.The measured R-X channels data are transformed to the signal-plus-noise channel and the noise channel before using in the estimation of the relaxation time distribution. The reduction of the number of data by sampling and averaging decreases significantly the computational time. The optimum $alpha$ (regularization parameter) depends on the corresponding slope of the plot of log$msb{10chi A}$ versus log$sb{10}alpha.$ Further, this optimum slope in log-log scale is inversely proportional to the number of data.A systematic parametric study reveals that the broadening of the estimated relaxation time distribution can be reduced by decreasing the noise level, decreasing the echo spacing, or using a sufficient range of data.

[发布机构] Rice University

[效力级别] engineering