Table 1.
T2 relaxation times (mean ± SD) measured with LASER, CP-LASER and T2ρ-LASER sequences and T2 ratios for CP-LASER and LASER and T2ρ-LASER and LASER obtained in the rat brain (n = 6) in vivo at 9.4 T. T2s of all measured metabolites were significantly longer (P < 0.05) with CP pulse sequences compared to LASER. T2 of water was also significantly longer with CP-LASER (P < 0.01) and T2ρ-LASER (P < 0.001) compared to LASER. Between CP-LASER and T2ρ-LASER sequences, the T2s of metabolites were not significantly different (P > 0.05) except in the case of water (P = 0.04). The high SDs observed for tCho and mIns were due to their T2 being longer than the maximum TE used in this study. The goodness of fit, R2 was > 0.9 for all metabolites except for the multiplet of NAA which was 0.88 with LASER.
| Spin systems | Compound | Group | LASER T2f (ms) | CP-LASER T2† (ms) | T2ρ-LASER T2ρ (ms) | T2†/T2f | T2ρ/T2f |
|---|---|---|---|---|---|---|---|
| Non-coupled and weakly coupled | Water | H2O | 44 ± 2 | 48 ± 2 | 50 ± 2 | 1.09 ± 0.07 | 1.16 ± 0.07 |
| NAA | 2CH3 | 321 ± 30 | 456 ± 26 | 449 ± 32 | 1.42 ± 0.16 | 1.40 ± 0.17 | |
| NAA | 3CH2 | 157 ± 41 | 187 ± 16 | 167 ± 25 | 1.19 ± 0.33 | 1.06 ± 0.32 | |
| tCr | N(CH3) | 170 ± 12 | 224 ± 7 | 231 ± 16 | 1.32 ± 0.10 | 1.36 ± 0.13 | |
| tCr | 2CH2 | 146 ± 16 | 175 ± 9 | 183 ± 20 | 1.20 ± 0.15 | 1.25 ± 0.20 | |
| tCho | entire molecule | 445 ± 67 | 523 ± 68 | ND | 1.17 ± 0.23 | - | |
| Strongly coupled | Glu | entire molecule | 70 ± 14 | 296 ± 44 | 270 ± 21 | 4.20 ± 1.02 | 3.84 ± 0.80 |
| Gln | entire molecule | 56 ± 12 | 116 ± 7 | 126 ± 19 | 2.08 ± 0.45 | 2.26 ± 0.58 | |
| mIns | entire molecule | 161 ± 26 | 584 ± 94 | 600 ± 90 | 3.62 ± 0.82 | 3.72 ± 0.82 | |
| taurine | entire molecule | 162 ± 28 | 355 ± 17 | 343 ± 27 | 2.19 ± 0.39 | 2.11 ± 0.40 |