Measuring Transverse Relaxation Rates Of The Major Brain Metabolites From Single-Voxel Press Acquisitions At A Single Te

Purpose To compare transverse relaxation rates of brain metabolites estimated from single-TE PRESS acquisitions with more conventionally derived rates estimated from multiple-TE PRESS acquisitions.Methods Single-voxel (8 mL) PRESS data within white matter from 6 subjects were acquired at five different TEs. Transverse relaxation rates R-2 of N-acetylaspartate, creatine, and choline were estimated from a single TE using full versus right-side-only sampling of the echo. These R-2 values were compared with R-2Hahn values obtained from the multiple-TE PRESS acquisitions.Results Following baseline subtraction and RMS weighting, interindividual mean R-2 values from TE = 288 ms magnitude spectra for choline, creatine, and N-acetylaspartate were highly correlated with respective R-2Hahn values (r(2) = 0.99). Paired individual measurements at this TE showed less correlation (r(2) = 0.48), primarily due to the N-acetylaspartate resonance. Using TE = 360 ms data for N-acetylaspartate and 288 ms for choline and creatine resulted in an improved correlation coefficient (r(2) = 0.80). The average absolute intra-individual differences in the estimated R(2)s between single-TE and Hahn method was 9.6 +/- 7.7%.Conclusion For the major brain metabolite singlets, R-2Hahn values showed correlations with more fragile measurements of R-2 from a single TE that are worthy of interest. Because the left side of long-TE spin echoes is available "for free" from an acquisition perspective, and although the single-TE method for estimating R-2 values is associated with lower precision, the reduction in scan time may be clinically helpful.