ABSTRACT Purpose To investigate the utility of a recently demonstrated diffusion MRI derived axon diameter surrogate measure (∆ D ⟂ ) under pathologic conditions induced by a spinal cord injury model. Methods Contusion injuries were performed on the thoracic–lumbar spinal cord of adult male rats. Eight weeks post‐injury, rats were sacrificed and their spinal cords imaged by MRI and then scanning electron microscopy (SEM). Relationships between the difference in radial diffusivity with diffusion time (∆ D ⟂ ) as well as longitudinal relaxometry based metrics and effective axon diameter from SEM were evaluated across regions of interest in slices 2–5 mm away from the injury epicenter. Results ∆ D ⟂ correlated strongly with histology derived effective axon diameter, while bound pool fraction and T 1 of the free proton pool ( T 1f ) had no significant correlations with effective axon diameter. A significant relationship was found between T 1f and ∆ D ⟂ across slices. Conclusion In the context of contusion injured rat spinal cords, ∆ D ⟂ serves as a robust surrogate for axon diameter and provides complementary information to longitudinal relaxometry derived metrics.
Alderson et al. (Sun,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: