LOCALIZED DOUBLE-SPIN-ECHO PROTON SPECTROSCOPY OF WEAKLY COUPLED HOMONUCLEAR SPIN SYSTEMS

The effect of localized double-spin-echo spectroscopy (PRESS) on a homonuclear weakly coupled AX spin system was calculated by the use of the product-operator formalism. Due to flip-angle distributions within the excited slices, different unwanted coherences are created which give rise to signal losses after the second and third RF pulse. The amount of signal loss is dependent on the timing of the sequence; i.e., only a proper choice of the time intervals between the pulses results in a high signal strength for coupled spins. Experiments were carried out on a Siemens Magnetom 1.5 T whole-body imager to verify the theory. Signal gains of far more than 100% were obtained for the coupled spins of lactate. © 1992.