Functional magnetic resonance imaging with intermolecular multiple-quantumcoherences

For the first time, we demonstrate here functional magnetic resonance imagi ng (fMRI) using intermolecular multiple-quantum coherences (iMQCs). iMQCs a re normally not observed in liquid-state NMR because dipolar interactions b etween spins average to zero. If the magnetic isotropy of the sample is bro ken through the use of magnetic field gradients, dipolar couplings dan reap pear, and hence iMQCs can be observed. Conventional (BOLD) fMRI measures su sceptibility variations averaged over each voxel. In the experiment perform ed here, the sensitivity of iMQCs to frequency variations over mesoscopic a nd well-defined distances is exploited. We show that iMQC contrast is quali tatively and quantitatively different from BOLD contrast in a visual stimul ation task. While the number of activated pixels is smaller in iMQC contras t, the intensity change in some pixels exceeds that of BOLD contrast severa lfold. (C) 2000 Elsevier Science Inc. All rights reserved.