Repeatability of Lac+ measurements in healthy human brain at 3 T

Purpose In vivo quantification of lactate has numerous applications in studying the pathology of both cerebral and musculoskeletal systems. Due to its low concentration (~0.5–1 mM), and overlap with lipid signals, traditional 1 H MR spectra acquired in vivo using a small voxel and short echo time often result in an inadequate signal to detect and resolve the lactate peak, especially in healthy human volunteers. Methods In this study, using a semi‐LASER acquisition with long echo time ( T E = 288 ms) and large voxel size (80 × 70 × 20 mm 3 ), we clearly visualize the combined signal of lactate and threonine. Therefore, we call the signal at 1.33 ppm Lac+ and quantify Lac+ concentration from water suppressed spectra in healthy human brains in vivo. Four participants (22–37 years old; mean age = 28 ± 5.4; three male, one female) were scanned on four separate days, and on each day four measurements were taken. Intra‐day values are calculated for each participant by comparing the four measurements on a single day. Inter‐day values were calculated using the mean intra‐day measurements. Results The mean intra‐participant Lac+ concentration, standard deviation (SD), and coefficient of variation (CV) ranged from 0.49 to 0.61 mM, 0.02 to 0.07 mM, and 4% to 13%, respectively, across four volunteers. The inter‐participant Lac+ concentration, SD, and CV was 0.53 mM, ±0.06 mM, and 11%. Conclusion Repeatability is shown in Lac+ measurement in healthy human brain using a long echo time semi‐LASER sequence with a large voxel in about 3.5 min at 3 T.