An investigation of glutamate quantification with PRESS and MEGA‐PRESS. (3rd December 2020)

• Record Type: Journal Article
• Authors: Cheng, Hu; Wang, Amanda; Newman, Sharlene; Dydak, Ulrike
• Is Part Of: NMR in biomedicine. Volume 34:Number 2(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-12-03
• Subjects: glutamate -- MEGA‐PRESS -- MRS -- phantom -- PRESS -- simulation; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.4453
• Languages: English
• ISSNs: 0952-3480

Abstract

Abstract : Glutamate is an important neurotransmitter. Although many studies have measured glutamate concentration in vivo using magnetic resonance spectroscopy (MRS), researchers have not reached a consensus on the accuracy of glutamate quantification at the field strength of 3 T. Besides, there is not an optimal MRS protocol for glutamate measurement. In this work, both simulation and phantom scans indicate that glutamate can be estimated with reasonable accuracy (<10% error on average) using the standard Point‐RESolved Spectroscopy (PRESS) technique with TE 30 ms; glutamine, however, is likely underestimated, which is also suggested by results from human scans using the same protocol. The phantom results show an underestimation of glutamate and glutamine for PRESS with long TE and MEGA‐PRESS off‐resonance spectra. Despite the underestimation, there is a high correlation between the measured values and the true values ( r > 0.8). Our results suggest that the quantification of glutamate and glutamine is reliable but can be off by a scaling factor, depending on the imaging technique. The outputs from all three PRESS sequences (TE = 30, 68 and 80 ms) are also highly correlated with each other ( r > 0.7) and moderately correlated ( r > 0.5) with the results from the MEGA‐PRESS difference spectra with moderate to good shimming (linewidth < 16 Hz). Abstract : Both simulation and phantom scans indicate that glutamate can be estimated with reasonable accuracy by PRESS with TE 30 ms (P_TE30). The phantom results show an underestimation of glutamate and glutamine for PRESS with long TE (P_TE80) and MEGA‐PRESS off‐resonance spectra (M_off). The measured values and the true values are highly correlated (r>0.8). The outputs from these three PRESS‐based sequences are also highly correlated (r>0.7) with each other and moderately correlated (r>0.5) with the results from MEGA‐PRESS difference spectra (M_diff).