High-resolution myelin water measurements in rat spinal cord.

Multiecho imaging data were acquired at 7T from control and injured (dorsal column transection) rat spinal cords ex vivo with in-plane resolution of 61, 78, and 100 microm, and from a control rat spinal cord in vivo with in-plane resolution of 117 microm. The myelin water maps were calculated using nonnegative least-squares (NNLS) analysis of the decay curves. For the control cords, myelin water maps showed details of the cord morphology, and the average myelin water fraction (MWF) values in white matter and gray matter corresponded well with previously published results and the expected amounts of myelin within the cord, and correlated very well with Luxol Fast Blue stain (R(2)=0.95). Myelin water maps from an injured cord showed excellent qualitative correlation with histology. This pilot study demonstrates that high-resolution myelin water mapping in rat spinal cord is feasible, and this technique has potential to be a valuable tool in studying white matter damage in rat models of spinal cord injury.