Detection of Glutathione from the Human Brain In 1H MRS By Simultaneous Acquisition of Signals from Both Double Quantum Coherence and Single Quantum Coherence Pathways
Abstract
Purpose
Glutathione (GSH) is a primary antioxidant in the human brain, supporting cognitive function. Detection of GSH in vivo by 1H MRS requires spectral editing due to large overlapping signals from other metabolites. Multiple quantum coherence (MQC) technique provides a way to detect the GSH signal in vivo. However, an intrinsic drawback of the MQC technique is that there is no other metabolite signal in the spectrum that can be used for postprocessing of data. In this study, we introduced a new sequence to solve the problem.
Methods
The sequence was developed on a 3T clinical MRI scanner. The sequence incorporates the MQC pathway of GSH and the single quantum coherence (SQC) pathway of the uncoupled NAA signal. The MQC pathway employs a frequency selective RF pulse for excitation of GSH resonance (2.95 ppm) followed by three other RF pulses for coherence transfer. The SQC pathway employs a frequency selective RF pulse for excitation of NAA resonance (2.01 ppm) and a refocusing pulse placed before the MQC pulse train. The deliberately designed coherence selection gradients enable the combined pathways of MQC GSH and SQC NAA. Spatial localization is achieved by a broadband refocusing pulse and two pairs of adiabatic inversion pulses combined with gradients. We performed experiments with both an MQC-only sequence and an MQC plus SQC sequence. Brain occipital lobe regions of the five subjects were studied twice with one hour interval between them.
Results
The new sequence enabled using the NAA peak for frequency drift assessment of individual transients and removal of unwanted transients. The resulting, averaged GSH signal had much higher reproducibility than the signal from the MQC-only sequence.
Conclusion
The new sequence is very promising for robust, reproducible measurement of GSH from the human brain. The approach is extendable for detection of other metabolites as well.