In vivo chemical shift imaging of gamma-aminobutyric acid in the human brain

A gradient-based multiple quantum filtering method is presented for in vivo chemical shift imaging of gamma-aminobutyric acid (GABA) in the human brai n, which provides effective suppression of the overlapping creatine singlet with close to optimal detection efficiency. It is shown by product operato r calculations and coherence pathway analysis that under conditions of no B -1 and B-0 inhomogeneity gradient filtering retains 75% of the two outer re sonance lines of the GABA-4 triplet with no creatine contamination, A varia tion of the method with 100% retention of the GABA-4 outer resonance lines but higher sensitivity to B-1 inhomogeneity is also discussed. By using a l ocalized version of the sequence with an 8 cm surface coil for transmission and detection, it was found in phantom experiments at 2.1 T that a 69% sig nal retention of the two outer resonance lines of the GABA-4 triplet was ac hieved relative to a spin echo sequence with inhibition of GABA J modulatio n. A creatine suppression ratio of 2000:1 was measured. The use of the meth od for chemical shift imaging of GABA is demonstrated by coronal images obt ained from phantoms and from the occipital robe of a healthy volunteer. Mag n Reson Med 41:35-42, 1999, (C) 1999 Wiley-Liss, Inc.