Diffusional anisotropy of T2 components in bovine optic nerve

A diffusion-CPMG hybrid experiment was used to analyze the diffusion characteristics of different T-2 relaxation components in bovine optic nerve. Data were collected using a pulsed field gradient (PFG) multi spin echo (MSE) CPMG sequence for parallel and perpendicular axon orientation and four diffusion times. The apparent diffusion coefficient (ADC) was evaluated for two observed T-2 components as a function of axonal orientation and diffusion time Delta. The short T-2 component exhibited minor diffusional anisotropy and larger ADC, whereas the long T-2 component showed significant anisotropy effects. This is consistent with the hypothesis that the short T-2 component is associated with water within the myelin sheath, which is less restricted than axonal water that is limited by cell membrane permeability.