Diana G Rotaru
King’s College, UK
Title: Towards direct and precise measurement of neurochemicals in psychiatry and neuroscience: Simultaneous spectral editing of GABA and glutathione with HERMES
Biography
Biography: Diana G Rotaru
Abstract
As the non-invasive evaluation of brain metabolism is considered an important factor in the understanding of neurological
and psychiatric disorders (Alzheimer’s Disease, Parkinson’s Disease, epilepsy, schizophrenia, autism, ADHD, psychosis,
bipolar disorder, major depressive disorder, etc.) more interest has been given to Magnetic Resonance Spectroscopy (MRS).
Based on recent work on spectral editing schemes, discrimination and quantification of otherwise unresolvable neurometabolites
like GABA (Gamma-Amino butyric Acid, the main inhibitory neurotransmitter) and GSH (glutathione, an
antioxidant found throughout the brain) becomes possible. The purpose of our study was to test if HERMES (Hadamard
Encoding and Reconstruction of MEGA-Edited Spectroscopy) could be used to discriminate between GABA and GSH. A
comparison with standard methods (MEGA-PRESS - MEshcher-GArwood Point REsolved Spectroscopy) and test-retest
reproducibility were also considered. A special proton MRS (1H-MRS) acquisition protocol was implemented on our 3T
MR750 General Electric scanner. The HERMES pulse sequence was then tested in phantom and in vivo experiments, for the
latter, a voxel in the dorso-medial prefrontal cortex (DMPFC) being prescribed. For the measurement of the edited signal,
two software packages were used: LC Model, along with FID-A pre- processing and Gannet, which currently can be used
without any additional pre-processing steps. The acquisition results showed that spectral editing was successfully performed,
with GABA and GSH being edited correctly considering the spectral appearance and the concentration values. Regarding
the analysis methods, LC Model and Gannet were both suitable for HERMES data sets. The test-retest reliability was assessed
based on the concentration values we obtained and suggests there was a strong consistency between test-retest results for
the same method of analysis. The advantages of the HERMES pulse sequence over conventional MR protocols include time
efficiency, high-quality results and cost- effectiveness. As such, with HERMES we were able to obtain GABA and GSH spectra
simultaneously in one scanning session no longer than 12 minutes, while the time required when using MEGAPRESS for the
both GABA&GSH is double, one session of 12 minutes being necessary for each metabolite. The long-term benefits of using
HERMES include the development of a reliable tool for neuroimaging research along with improved healthcare solutions
(patient stratification, early disease detection, accurate diagnosis, treatment tracking and drug therapy evaluation).