Optimization of timing in the Carr-Purcell-Meiboom-Gill sequence

The Carr-Purcell-Meiboom-Gill sequence is widely used in grossly inhomogene ous fields to characterize fluid saturated porous media. The distribution o f T-2 relaxation times is a measure of the distribution of pore sizes. We p resent here a theoretical analysis of the spin dynamics of this sequence in strongly inhomogeneous fields. Based on this analysis, we optimize the tin ting of the sequence for maximal signal bandwidth. It is shown that the ini tial pulse spacing should be decreased by a time 2t(90)/pi. Experimental re sults in a strayfield set-up confirm the theoretical analysis. The optimize d timing increases the measured signal bandwidth and increases the ratio of signal-to-noise by 1.2 dB without affecting the measured relaxation time. (C) 2001 Elsevier Science Inc. All rights reserved.