In vivo T 2 relaxation time measurement with echo‐time averaging

• Published in: NMR in biomedicine Vol. 27; no. 8; pp. 863 - 869
• Main Authors: Prescot, Andrew P., Shi, Xianfeng, Choi, Changho, Renshaw, Perry F.
• Format: Journal Article
• Language: English
• Published: 01.08.2014
• DOI: 10.1002/nbm.3115
• ISSN: 0952-3480

The accuracy of metabolite concentrations measured using in vivo proton ( 1 H) MRS is enhanced following correction for spin–spin ( T 2 ) relaxation effects. In addition, metabolite proton T 2 relaxation times provide unique information regarding cellular environment and molecular mobility. Echo‐time (TE) averaging 1 H MRS involves the collection and averaging of multiple TE steps, which greatly simplifies resulting spectra due to the attenuation of spin‐coupled and macromolecule resonances. Given the simplified spectral appearance and inherent metabolite T 2 relaxation information, the aim of the present proof‐of‐concept study was to develop a novel data processing scheme to estimate metabolite T 2 relaxation times from TE‐averaged 1 H MRS data. Spectral simulations are used to validate the proposed TE‐averaging methods for estimating methyl proton T 2 relaxation times for N ‐acetyl aspartate, total creatine, and choline‐containing compounds. The utility of the technique and its reproducibility are demonstrated using data obtained in vivo from the posterior‐occipital cortex of 10 healthy control subjects. Compared with standard methods, distinct advantages of this approach include built‐in macromolecule resonance attenuation, in vivo T 2 estimates closer to reported values when maximum TE ≈  T 2 , and the potential for T 2 calculation of metabolite resonances otherwise inseparable in standard 1 H MRS spectra recorded in vivo . Copyright © 2014 John Wiley & Sons, Ltd.