POLARIZATION-TRANSFER EFFECTS IN LOCALIZED DOUBLE-SPIN-ECHO SPECTROSCOPY OF WEAKLY COUPLED HOMONUCLEAR SPIN SYSTEMS

In point-resolved spectroscopy (PRESS), fast echo-time-dependent signa l modulations of the multiplets of weakly coupled homonuclear spin sys tems occur, They are caused by polarization-transfer effects that are explained by calculations with the product-operator formalism, The imp act of slice profiles and transmitter adjustment and the difference of the polarization-transfer effects between AX and AX, systems are expl ained. Experiments with echo-time variation were performed with slice- selective pulses of different quality of profile. Experiments were car ried out with a solution of calcium lactate in a 1.5 T Siemens whole-b ody imager, The experimental results confirm the theoretical calculati ons, It is stated that in localized double-spin-echo spectroscopy, esp ecially at echo times of TE = 2/J, the polarization-transfer effects m ust be considered, This knowledge is important in lactate spectroscopy in vivo, where the assumptions for 2/J range between 270 and 290 ms, leading to different signal intensities of lactate in PRESS spectra. ( C) 1995 Academic Press, Inc.