Abstract
To assess reproducibility of glutamate measurement in the human brain by two short echo time (TE) 1H-MRS sequences [stimulated echo acquisition mode (STEAM) and semi-localized by adiabatic selective refocusing (sLASER)] at 7 T. Reliable assessment of glutamate is important when studying a variety of neurological and neuropsychiatric disorders. At 7 T, the glutamate signal can be separated from the glutamine signal and hence more accurately measured as compared to lower field strengths. A sLASER sequence has been developed for 7 T, using field focusing at short TE, resulting in twice as much signal as can be obtained using STEAM and improved localization accuracy due to a decreased chemical shift artifact. Eight subjects were scanned twice using both STEAM and sLASER. Data were acquired from the frontal and occipital brain region. Subsequently, intraclass correlations were computed for the estimated metabolite concentrations. sLASER has higher ICC's for glutamate concentration as compared to STEAM in both the frontal and occipital VOI, which is probably due to the higher sensitivity and localization accuracy. We conclude that sLASER 1H-MRS at 7 T is a reliable method to obtain reproducible measures of glutamate levels in the human brain at such high accuracy that individual variability, even between age-matched subjects, is measured.
Highlights
In vivo 1H magnetic resonance spectroscopy (1H-MRS) can be used to determine glutamate levels in the human brain
We estimated the reproducibility of glutamate measurements using the stimulated echo acquisition mode (STEAM) and semi-localized by adiabatic selective refocusing (sLASER) sequence at 7 T in two different areas of the human brain
In the frontal brain region that plays an important role in psychiatric disorders [14,15,16,17,18], glutamate concentrations measured with sLASER show a high reproducibility
Summary
In vivo 1H magnetic resonance spectroscopy (1H-MRS) can be used to determine glutamate levels in the human brain. Glutamate is the primary excitatory neurotransmitter in the mammalian central nervous system. Examining glutamate levels is important when studying a variety of neuropsychiatric conditions, including schizophrenia, bipolar disorder, depression, Alzheimer’s dementia, and anxiety disorders [1]. The majority of studies examining glutamate in psychiatric disorders using 1H-MRS were conducted at magnetic field strengths of 4 T or lower. Measurement of glutamate with 1H-MRS is challenging at lower field strengths, due to its spectral overlap with glutamine. A magnetic field strength of 7 T results in an increased signalto-noise ratio (SNR) and in an increased chemical shift dispersion.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
