OPTIMIZATION OF HOMONUCLEAR 2-DIMENSIONAL CORRELATION METHODS FOR IN-VIVO AND EX-VIVO NMR

The efficiency of high-field homonuclear H-1 two-dimensional correlation experiments for in vivo and ex vivo conditions is investigated. Problems associated with experiments on tissues and organs are reviewed. An optimized 2D correlation experiment is proposed which takes into account the specific features described. Since the lineshapes in living samples are determined principally by field inhomogeneity rather than by spin-spin re laxation, the coherence-transfer signal is an echo in t(2), amplitude modulated in t(1). From the analysis of this time-domain signal, it is shown that significant experimental time can be gained by carefully adjusting the acquisition boundaries as a function of the characteristics of the spin systems of interest. The S/N ratio can be improved further by using matched filtering in t(2) (which is greatly facilitated by the use of a SECSY experiment rather than a COSY one), as well as by apodizing the signal in the t(1) domain, during acquisition rather than during processing. Experimental results obtained with a phantom, as well as in vivo in the rat brain at 4.7 T, are presented. (C) 1995 Academic Press, Inc.