Imaging the Transformation of Ipsilateral Internal Capsule Following Focal Cerebral Ischemia in Rat by Diffusion Kurtosis Imaging

Background: The purpose of our study is to explore the relationship between recovery of neural function and transformation of the internal capsule (IC) after transient middle cerebral artery occlusion (MCAO) by using diffusion kurtosis imaging (DKI). Methods: Six male adult Sprague-Dawley rats implemented with transient MCAO were used in this study. Sensorimotor function was assessed according to repetitive behavioral testing on day 1, 3, 7, 14, and 28 after cerebral ischemia. Metrics of DKI were acquired, and the time course of the region-to-normal ratio was evaluated in IC. Results: After cerebral ischemia, relative fractional anisotropy in IC decreased on day 3 (P <.01). Relative mean diffusivity (rMD) increased on day 28 (P <.05). Relative mean diffusional kurtosis (rMK) increased on day 3 (P <.01) and decreased on day 7 (P <.05). Relative axial diffusional kurtosis (rKa) increased on day 3 (P <.01) and declined on day 7 (P <.05). Relative radial diffusional kurtosis (rKr) was reduced on day 7 (P <.05). Changes in rMK were larger than changes in rMD on day 3 (P <.05). The factor of rKa and rKr revealed marked difference on day 7 (P <.05) and day 14 (P <.05). Neurological function score showed that rats exhibited functional recovery from day 7 (P <.01) post stroke. Conclusions: This longitudinal multiparametric magnetic resonance imaging study suggested that K metrics offers information complimentary to conventional diffusion metrics and revealed the procedure during the structural modification in the ipsilateral IC following focal cerebral ischemia. After transient MCAO, the neural transformation occurred in a time-dependent procedure.