Population means and 99% normal ranges (in parentheses) of fiber number, tract volume, and MR parameter medians across our population of healthy individuals. Data obtained at 3T.
| Reconstruction Type | No. of fibers | Vol. (cm2) | T1 (ms) | T2 (ms) | MTR | FA | MD (×104 mm2/s) | λ1 (×104 mm2/s) | λ2 (×104 mm2/s) | λ3 (×104 mm2/s) | λ⊥ (×104 mm2/s) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of individuals | 20 | 20 | 11 | 17 | 15 | 20 | 20 | 20 | 20 | 20 | 20 |
| Whole brain | 240 (−120, 610) | 3.3 (0.039, 6.5) | 930 (680, 1180) | 91 (80, 102) | 0.46 (0.44, 0.49) | 0.58 (0.51, 0.66) | 7.9 (7.3, 8.5) | 14 (13, 16) | 6.2 (5.4, 7.1) | 3.8 (3.0, 4.6) | 5.0 (4.2, 5.8) |
| Hemispheres | 1100 (28, 2200) | 4.4 (1.7, 7.0) | 810 (610, 1000) | 92 (82, 101) | 0.45 (0.43, 0.48) | 0.57 (0.46, 0.67) | 7.7 (7.1, 8.3) | 13 (12, 15) | 6.2 (5.3, 7.0) | 3.8 (2.7, 4.8) | 5.0 (4.1, 5.9) |
| Brain stem | 470 (−350, 1300) | 0.81 (0.14, 1.5) | 1040 (780, 1300) | 92 (68, 116) | 0.48 (0.44, 0.52) | 0.59 (0.50, 0.68) | 8.4 (7.2, 9.6) | 15 (12, 18) | 6.4 (5.2, 7.6) | 4.0 (2.8, 5.2) | 5.2 (4.1, 6.3) |
Note:—MTR indicates magnetization transfer ratio; FA, fractional anisotropy; MD, mean diffusivity; λ⊥, transverse diffusivity (average of λ2 and λ3).