In vivo relaxation times of gray matter and white matter in spinal cord

In vivo relaxation times and relative spin densities of gray matter (GM) and white matter (WM) of rat spinal cord were measured. Inductively coupled implanted RF coil was used to improve the signal-to-noise ratio required for making these measurements, The estimated relaxation times tin milliseconds) are: T-1(GM) = 1021 +/- 93, T-2(GM) = 64 +/- 3.4, T-1(WM) = 1089 +/- 126, and T-2 (WM) = 79 +/- 6.9, The estimated relative spin densities are: rho (GM) (60 +/- 2.3)% and rho (WM) = (40 +/- 2.1)%, The T-1 values of GM and white matter are not statistically different. However, the differences in T-2 values and spin densities of GM and WM are statistically significant. These in vivo measurements indicate that the observed contrast between GM and WM in spinal cord MR images mainly arises from the differences in the spin density. (C) 1999 Elsevier Science Inc.