Myelin water and T2 relaxation measurements in the healthy cervical spinal cord at 3.0T: Repeatability and changes with age

Multiecho T-2 relaxation measurements offer specific information about myelin content through the myelin water fraction (MWF), as well as about the water environments through the intra- and extra-cellular (IE), and global, geometric mean T-2 (GMT(2)) times. While these measurements have yielded new insights into brain development and pathologies, they have yet to be thoroughly investigated in the spinal cord. The goals of this study were: (1) to apply a new 3D multiecho T-2 relaxation measurement in the cervical spine with sufficient axial resolution to distinguish grey and white matter; (2) to perform a pilot reliability assessment of the resulting MWF and GMT(2) measures in a target population; and (3) to detect differences in these measures between a younger cohort (20-30 years of age) and an older cohort (50-75 years of age) of healthy adults. The results demonstrated that the MWF in younger healthy adults follows the known pattern of lower myelin content in grey matter (mean (95% confidence interval)) (0.049 (0.030-0.067)) as compared to white matter (0.296(0.275-0.317), p<0.001). The reliability coefficients were 0.65 and 0.82 for the MWF in the dorsal (DC) and lateral column (LC) white matter, respectively; 0.79 and 0.52 for the IE GMT(2); and 0.74 and 0.73 for the global GMT(2). Significantly lower MWF were found in the older adults than in the younger adults (DC p = 0.014; LC p = 0.012), as well as lower IE GMT(2) times (DC p = 0.008; LC p = 0.042), however, the global GMT(2) times did not show any differences. These changes in MWF and IE GMT(2) times, but not in global GMT(2) times, indicate that multiecho T-2 relaxation measures are sensitive to changes in myelin integrity and cell morphology that may not be apparent on conventional T-2 weighted images. (C) 2010 Elsevier Inc. All rights reserved.