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

Abstract

Purpose: To develop an experimental approach for determining in vivo transverse relaxation rates (T₂) of metabolites that are detected by spectral editing without using simulations, and to demonstrate this approach to measure the T₂ of γ‐aminobutyric acid (GABA). Materials and Methods: The proposed method first determines the TE‐dependence of the edited signals using measurements in a pure phantom solution (10 mM γ‐aminobutyric acid; GABA); the phantom T₂ is also determined. Once the editing echo time (TE) ‐modulation pattern is known, it can then be used to determine T₂ in vivo. The method was applied to measure GABA T₂ in the occipital lobe of five healthy adult subjects at 3T, using a J‐difference editing method. Unwanted macromolecular contributions to the GABA signal were also measured. Results: The in vivo T₂ of edited GABA signal was 88 ± 12 ms; this preliminary result is somewhat shorter than other metabolite T₂ values in the literature at this field strength. Conclusion: Spectral editing methods are now widely used to detect low concentration metabolites, such as GABA, but to date no edited acquisition methods have been proposed for the measurement of transverse relaxation times (T₂). The method described has been successfully applied to measuring the T₂ of GABA. J. Magn. Reson. Imaging 2012;35:229‐234.