A new method for fast proton spectroscopic imaging: spectroscopic GRASE.
A new fast spectroscopic imaging method is presented which allows both a very short minimum total measurement time and effective homonuclear decoupling. After each excitation, all data points from N(GE) k(x)-k(y)-slices at different k(omega)-values are acquired by using a gradient and spin echo (GRASE) imaging sequence. The delay between consecutive gradient echoes, which are measured with uniform phase encoding between consecutive refocusing alpha-pulses, is the inverse of the spectral width (SW). A refocusing 180 degrees pulse, which is applied within a constant delay between excitation and the GRASE sequence, is shifted in a series of measurements by an increment N(GE)/(2 * SW) to cover the whole k(omega)-k(x)-k(y)-space. Spectroscopic GRASE was implemented on a 4.7 T imaging system and tested on phantoms and normal rat brain in vivo. Measurements were performed with a nominal voxel size of 1.5 x 1.5 x 3 mm(3) and a spatial 64 x 64 matrix. The total measurement time was 2 or 4 min using a repetition time of 1.9 sec, 96 chemical shift encoding steps, SW = 800 Hz, N(GE) = 3, and 2 or 4 accumulations.
Dreher
W
W
Universität Bremen, Fachbereich 2 (Biologie/Chemie), Bremen, Germany. dreher@tomo.uni-bremen.de
Leibfritz
D
D
D000818:Animals; D001921:Brain / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging / Q000379:methods; D051381:Rats; D013057:Spectrum Analysis / Q000379:methods*