Measuring T2 in vivo with J‐difference editing: Application to GABA at 3 tesla

摘要: Proton Magnetic Resonance spectroscopy (1H-MRS) is a useful technique to probe in vivo biochemical status noninvasively, which has been widely applied study the brain both clinical and neuroscience settings. If tissue water content known, metabolite concentrations are often calculated from relative intensities of signals (1), making appropriate corrections for longitudinal transverse relaxation (characterized by time constants T1 T2, respectively). Thus, measurement parameters an important prerequisite absolute quantification MR spectra. In times (T2) usually measured localized single-voxel measurements at range echo (TE). For singlet resonances, such as N-acetyl aspartate (NAA), creatine (Cr) choline (Cho), TE-dependent decay signal intensity can generally be modeled single exponential with constant T2; T2s have this way field strengths (2–7). The TE-dependence coupled spin systems more complicated, because their modulated T2 scalar coupling evolution. glutamate modeling TE dependence Glutamate (8). However, many metabolites (such γ-aminobutyric acid [GABA] (9), glutathione (10), ascorbate (11), NAAG (12)), low amplitude overlap hamper detection using conventional MRS methods, it usual use spectral editing methods detect them reliably. To best our knowledge, no method published date that able measure detected techniques. There considerable recent interest inhibitory neurotransmitter, GABA, investigating role GABA disease, relationships between functional imaging (13–15) behavior (16–19). although extensively investigate individual group differences levels, they not truly quantitative, human previously measured. Relative kind, quantified institutional units (i.u.), inferences separately studies, within centers. most common these studies J-difference implemented through MEGA-PRESS (20), detecting intermediate (~70 ms). Because similar length typical (and therefore anticipated GABA), measuring step quantitative. It also known “GABA” 3.0 ppm standard techniques 3 Tesla (T) contains appreciable contribution macromolecules (MM) partner 1.7 (20). presence MM resonance needs accounted for, determination estimation “pure” concentrations. In study, we present framework edited metabolites, entirely experimental does rely upon simulation, demonstrate 3T.