Tissue orientation effects on T2 relaxation in fresh and fixed spinal cord white matter

In this study, we investigated the orientation dependence of T2 in fresh and fixed spinal cord white matter (WM). Scans from three pig spinal cord tissues were acquired at 7T at 6 different orientations with respect to the main magnetic field. We found a considerable orientation dependence in the short fraction relaxation rate R2 (=1/T2) in fresh WM as opposed to a weak orientation effect in fixed WM. To our knowledge, this is the first direct comparison of orientation dependence in a WM tissue sample in the fresh and fixed state. Orientation dependence was not observed in long fraction R2.