DECOMPOSITION OF INFLOW AND BLOOD-OXYGEN LEVEL-DEPENDENT (BOLD) EFFECTS WITH DUAL-ECHO SPIRAL GRADIENT-RECALLED ECHO (GRE) FMRI

Image contrast with gradient-recalled echo sequences (GRE) used for fM RI can have both blood oxygen level-dependent (BOLD) and inflow compon ents, and the latter is often undesirable, A dual-echo technique can b e used to differentiate these mechanisms, because modulation of signal from inflow is common to both echoes, whereas susceptibility and diff usion-related signal losses are larger in the second echo, An efficien t dual-echo interleaved spiral sequence was developed for use with a c onventional scanner. It uses a k-space trajectory that spirals out fro m the origin while the first echo is collected, then spirals back in w hile collecting the second echo. Decomposition of the data provides se parate images of the inflow and T-2-weighted components. Results demo nstrate the decomposition with phantom experiments and with photic sti mulation in normal volunteers.