title: In vivo T(2) relaxation time measurement with echo-time averaging.
abstract: The accuracy of metabolite concentrations measured using in vivo proton ((1) H) MRS is enhanced following correction for spin-spin (T2 ) relaxation effects. In addition, metabolite proton T2 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 T2 relaxation information, the aim of the present proof-of-concept study was to develop a novel data processing scheme to estimate metabolite T2 relaxation times from TE-averaged (1) H MRS data. Spectral simulations are used to validate the proposed TE-averaging methods for estimating methyl proton T2 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 T2 estimates closer to reported values when maximum TE ≈ T2 , and the potential for T2 calculation of metabolite resonances otherwise inseparable in standard (1) H MRS spectra recorded in vivo.
authors.affiliation: Brain Institute, University of Utah, Salt Lake City, UT, USA; Department of Radiology, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Prescot
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Shi
authors.forename: Changho
authors.initials: C
authors.lastname: Choi
authors.forename: Perry F
authors.initials: PF
authors.lastname: Renshaw
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D002794:Choline / Q000378:metabolism; D003198:Computer Simulation; D003401:Creatine / Q000378:metabolism; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D055442:Metabolome; D011522:Protons; D012015:Reference Standards; D012044:Regression Analysis; D013997:Time Factors
chemical_list: D011522:Protons; D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline
keywords: echo-time averaging; proton MRS; spin-spin (T2) relaxation time