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Table 1: 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).

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)