Masafumi Harada MD, PhD, Presenter: Nothing to Disclose

Hitoshi Kubo, Abstract Co-Author: Nothing to Disclose

Minoru Sakama PhD, Abstract Co-Author: Nothing to Disclose

Masako Minato MD, Abstract Co-Author: Nothing to Disclose

Hiromu Nishitani MD, PhD, Abstract Co-Author: Nothing to Disclose

Tsuyoshi Matsuda BS, Abstract Co-Author: Nothing to Disclose

Gamma-amino butyric acid (GABA) is one of the neurotransmitter agent which is mainly dominant in suppressive neurons. Recently GABA was measured using proton MR spectroscopy by editing technique and MEGA-PRESS has several advantages for mechanical environment and is useful for clinical setting. The initial purpose of this study was to observe regional difference of absolute GABA concentration in the human brain by MEGA-PRESS and to find changes of GABA concentration by administration of psychotropic drug.

Our created MEGA-PRESS employs gradients surrounding the frequency selective pulses at 1.9 ppm to dephase transverse magnetization. The sequence parameter was as following: TR = 1500 ms, TE = 68 ms, ROI = 3.0 x 3.0 x 3.0 cm3 (27ml), summation = 256 signals for each spectrum, total acquisition time = 13 min. The measurements with and without the frequency selective pulses were conducted alternatively. The difference of the acquired spectra provided an edited spectrum of GABA. The in-vitro data of NAA, Glutamine, Glutamate and GABA were acquired by MEGA-PRESS and set as a basis-set for LCModel. The subjects were ten normal volunteers (5 male, 5 female, age 25 -32 years ) and the measurements of GABA were conducted in left lenticular nucleus, left parietal white matter and right hemisphere of the cerebellum before and after administration of psychotropic drugs.

The peak of GABA was found at 3.02 ppm and those of Glx and macromolecule were observed in this spectrum. The concentration of GABA in the cerebellum was the highest in three regions and that in the parietal white matter was the lowest, which was consistent with the previous reports. The increase of GABA after administration of benzodiazepine was found by 5 subjects in total 10 subjects, but GABA increase was observed in all subjects after administration of Li.

GABA in the human brain could be measured in the clinical setting and psychotropic agents would be influential of metabolism of GABA. This result may indicate that MEGA-PRESS on 3T MRI shows individual estimation of psychotropic effect by drug administration.

Harada, M, Kubo, H, Sakama, M, Minato, M, Nishitani, H, Matsuda, T, Regional Difference and Drug Influence of GABA Concentration in Human Brain Measured by MEGA-PRESS with LC Model Fitting on Clinical 3T Apparatus.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4416050.html