Measurement of T2* in the human spinal cord at 3T.

Abstract

To measure the transverse relaxation time T2* in healthy human cervical spinal cord gray matter (GM) and white matter (WM) at 3T. Thirty healthy volunteers were recruited. Axial images were acquired using an averaged multi-echo gradient-echo (mFFE) T2*-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 T2* for each voxel. No global difference in T2* 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 T2* was longer than superior T2* in GM (44.7ms vs. 40.1ms; p<0.01) and in WM (41.8ms vs. 35.9ms; p<0.01). Significant differences in T2* 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 T2* in the healthy cord. These values of T2* in the spinal cord are notably lower than most reported values of T2* in the cortex.