BAND-SELECTIVE SPIN ECHOES FOR IN-VIVO LOCALIZED H-1-NMR SPECTROSCOPY

This study describes a new single spin-echo spatial localization seque nce, BASSALE or BAnd-Selective Spin echo Acquisition for Localized Edi ting, that overcomes a number of the limitations of the STEAM and PRES S volume selection pulse sequences. It achieves conformal volume local ization in a single shot by spatially tailored suppression of all magn etization outside a 2D region of interest followed by selection of a s ingle orthogonal slice. This separation of spatial localization from t he echo formation process has permitted use of a spectrally selective cosine-modulated sine refocusing pulse to acquire localized H-1 spectr a with the water suppression efficiency of STEAM and the sensitivity o f PRESS. Echoes formed by such spectrally selective pulses have been t ermed band-selective spin echoes. The BASSALE sequence attains shorter echo times than PRESS, inhibits scalar spin-spin interactions to perm it localized editing and T-2 relaxometry of metabolites with J-coupled spins (e.g., lactate), is insensitive to homonuclear multiple quantum and polarization transfer effects, and can be made sensitive or insen sitive to spin displacement effects. Applications are shown both with phantoms and in situ in the rat brain.