Semi-LASER H-1 MR Spectroscopy at 7 Tesla in Human Brain: Metabolite Quantification Incorporating Subject-Specific Macromolecule Removal.

Authors

Jacob Penner, Centre for Functional and Metabolic Mapping (CFMM), Robarts Research Institute, University of Western Ontario, London, Canada.
Robert Bartha, Department of Medical Biophysics, University of Western Ontario, London, Canada.

Document Type

Article

Publication Date

7-1-2015

Journal

Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine

Volume

74

Issue

1

First Page

4

Last Page

12

URL with Digital Object Identifier

10.1002/mrm.25380

Abstract

Purpose

To develop an in vivo ¹H short-echo-time semi-LASER spectroscopy protocol at 7 Tesla (T) incorporating subject-specific macromolecule removal.

Methods

T₁ constants of the major metabolites were measured with little macromolecule contribution in seven healthy volunteers and used to optimize double inversion metabolite nulling. Spectra were acquired from parietal–occipital cortex of five healthy volunteers. Metabolite-nulled macromolecule spectra were subtracted from the metabolite spectra before fitting in the time domain with prior-knowledge templates. Absolute metabolite concentrations were determined by referencing to the water signal, following partial volume and relaxation corrections.

Results

The average signal to noise ratio, N-acetylaspartate peak height divided by the baseline noise standard deviation, was 48 ± 6. T₁ constants for N-acetylaspartate, glutamate, creatine, and choline were 1.71 ± 0.15 s, 1.68 ± 0.19 s, 1.63 ± 0.10 s, and 1.41 ± 0.09 s, respectively. The optimal double inversion times for metabolite suppression were TI₁ = 2.09 s and TI₂ = 0.52 s. The coefficient of variation was less than 10% for N-acetylaspartate, creatine, choline, and myo-inositol, and less than 20% for glutamate and glutamine.

Conclusion

Short echo-time ¹H semi-LASER spectroscopy at 7T incorporating subject-specific macromolecule removal yielded reproducible brain metabolite concentrations ideal for applications in disease conditions where macromolecule contributions may deviate from the norm. Magn Reson Med 74:4–12, 2015. © 2014 Wiley Periodicals, Inc.

Notes

This article is freely available to read from the journal