Measurement of T-2* in the human spinal cord at 3T

Purpose To measure the transverse relaxation time T-2* in healthy human cervical spinal cord gray matter (GM) and white matter (WM) at 3T. Methods Thirty healthy volunteers were recruited. Axial images were acquired using an averaged multi-echo gradient-echo (mFFE) T-2*-weighted sequence with 5 echoes. We used the signal equation for an mFFE sequence with constant dephasing gradients after each echo to jointly estimate the spin density and T-2* for each voxel. Results No global difference in T-2* was observed between all GM (41.3 5.6ms) and all WM (39.8 +/- 5.4ms). No significant differences were observed between left (43.2 +/- 6.8ms) and right (43.4 +/- 5.5ms) ventral GM, left (38.3 +/- 6.1ms) and right (38.6 +/- 6.5ms) dorsal GM, and left (39.4 +/- 5.8ms) and right (40.3 +/- 5.8ms) lateral WM. However, significant regional differences were observed between ventral (43.4 +/- 5.7ms) and dorsal (38.4 +/- 6.0ms) GM (p<0.05), as well as between ventral (42.9 +/- 6.5ms) and dorsal (37.9 +/- 6.2ms) WM (p<0.05). In analyses across slices, inferior T-2* was longer than superior T-2* in GM (44.7ms vs. 40.1ms; p<0.01) and in WM (41.8ms vs. 35.9ms; p<0.01). Conclusions Significant differences in T-2* are observed between ventral and dorsal GM, ventral and dorsal WM, and superior and inferior GM and WM. There is no evidence for bilateral asymmetry in T-2* in the healthy cord. These values of T-2* in the spinal cord are notably lower than most reported values of T-2* in the cortex.