Detection And Evaluation Of GABA Concentration In Brain By MEGA-PRESS Sequence In 3T

In the brain, gamma-aminobutyric acid (GABA) and Glutamate (Glu) are very important inhibitory and excitatory neurotransmitters. Their collaboration plays critical roles in regulating the transmission of excitement, function of emotional and conscious processing. These neurotransmitters have an effect on GABAergic and glutamatergic neurons respectively. Though with very low levels in the brain, GABA directly or indirectly mediate almost 30% neuron synapses and widely exist in the cerebral cortex, hippocampus, substantia nigra nucleus area. Concentration of GABA in the default network is of great sense to express the individual functions and has a relationship with the subtle response differences in stimulation experiments. Indeed, dysfunction of GABA is strongly linked to a variety of psychiatric or neurological problems, such as schizophrenia, depression, epilepsy. Therefore, it is of great significance to find a real-time way to detect GABA efficiently.In 2011, a epidemiological investigation concerning epilepsy primarily carried out in east and southwest China reveals that epileptic incidence is almost 5% o in our country. Result shows that the first onset period especially happens in people’s childrenhood or adolescence, which causes great pain to patients and their families. Accurate localization of epileptogenic source is very important for judgment or treatment of epilepsy as well as assessment of the curative effect. At present, the common auxiliary diagnosis methods of epilepsy include EEG, magnetic resonance imaging, but technology which can trace of biological molecules metabolism is scarce. Magnetic resonance spectroscopy, the only non-invasive and no radiation imaging method, had been widely used in detection of brain metabolite, like N-acetylaspartate (NAA), creatine (Cr), choline (Cho). MEGA-PRESS sequence achieves detection of regional variations of GABA concentration by/-difference spectral editing theory. Accordingly, projects are designed to explore repeatability of metabolites detected by MEGA-PRESS in this article. Furthermore, data are analyzed to examine if there exists regional difference feature of GABA. The main contents and results are as follows:(1) 14 healthy volunteers (7 males and 7 females, Mean age:26±4 yrs.) were recruited for the scans. Repeatability of metabolites detected by MEGA-PRESS was verified by repeated measurements of all the healthy volunteers. The result demonstrates good repeatability of GAB A in both ACC and OCC region (ICC of ACC: 0.547, ICC of OCC:0.853). And ratio of the two metabolites, like GABA+/Cr, GABA+/Cho, is of greater stability than single metabolite like GABA+.(2) The concentration of GABA+ in OCC was higher than that in ACC. And the discrepancy between ACC and OCC reveals obvious region-specific feature (p<0.01). Meanwhile, linear regression analysis exhibits noteworthy linear relationship between GM ratio and GABA+ concentration in VOI of OCC while result in ACC was poor.(3) However, no significant metabolic change of GABA+ was found in epilepsy patients compared with healthy volunteers in OCC region.