Self‐diffusion in CNS tissue by volume‐selective proton NMR

We have used a volume-selective NMR pulse sequence to measure the diffusion coefficient (D) inside a selected cuboid volume. The sequence is a variant of the stimulated echo method for volume-selective spectroscopy, and allows sequential measurement of D in any of three orthogonal directions and for a range of diffusion times. The echo attenuation from which D is calculated is free from the cross terms that can arise because of interactions between volume selection and diffusion-sensitizing gradients. Anisotropic and diffusion-time-dependent behavior is observed in brain structures known to have axon fibers aligned primarily in one direction.