Detection of homonuclear decoupled in vivo proton NMR spectra using constant time chemical shift encoding: CT-PRESS

A new pulse sequence, termed CT-PRESS, is presented, which allows the detec tion of in vivo H-1 NMR spectra with effective homonuclear decoupling. A PR ESS sequence with a short echo-time TE, used for spatial localization, is s upplemented by an additional 180 degrees pulse. The temporal position of th is 180 degrees pulse is shifted within a series of experiments, while the t ime interval between signal excitation and detection is kept constant. CT-P RESS is a two-dimensional (2D) spectroscopic experiment as far as data acqu isition and processing are concerned, although only diagonal signals are ge nerated in the 2D spectrum. However, since the principle of constant time c hemical shift encoding is used in the t(1) domain, effective homonuclear de coupling is obtained by projecting the 2D spectrum onto the corresponding f (1) axis. Thus, good spectral resolution and high signal-to-noise ratio are obtained. The main advantage, as compared to localized 2D J-resolved MRS, is that optimized experiments can be performed for coupled resonances of in terest by choosing the sequence parameters dependent on the type of multipl ets, the J-coupling constants and T-2. Major fields of application will be parametric studies on coupled resonances, (e.g., T-1, diffusion behavior or magnetization transfer) and/or the detection of spatial and temporal chang es of metabolites with coupled spin systes. (C) 1998 Elsevier Science Inc.