Abstract:

Objective

To demonstrate the feasibility of multi-shell diffusion magnetic resonance imaging （MRI） techniques in characterizing microstructural changes in brain tissue during ischemic stroke.This study evaluates the differences， specificity and sensitivity of diffusion metrics.

Methods

We established a middle cerebral artery occlusion-reperfusion （MCAO/R） model in rats. Using a 9.4T small animal in vivo magnetic resonance imaging system， we collected multi-shell diffusion data， and analyzed a typical diffusion tensor imaging （DTI） model， and two advanced models diffusion kurtosis imaging （DKI）， and neurite orientation dispersion and density imaging （NODDI）， within the framework of multi-shell diffusion magnetic resonance imaging. Paired t-tests， receiver operating characteristic （ROC） curve and area under the curve（AUC） were employed to assess the specificity and sensitivity of diffusion metrics.

Results

Compared to the contralateral normal region， significant differences were observed in all NODDI indices： orientation dispersion index （ODI）， neurite density index （NDI）， and volume fraction of isotropic water （FISO） on the infarcted side（P＜0.001）， with NODDI metrics demonstrating high detection performance. Both NDI and the DKI index showed similar capabilities in detecting disease progression. NDI and DKI showed similar capabilities in detecting disease progression. Furthermore， NODDI-related metrics were consistent with histological analysis results.

Conclusion

Multi-shell diffusion magnetic resonance imaging exhibits high sensitivity in detecting and revealing microstructural changes in brain tissue during ischemic stroke， establishing a crucial foundation for the clinical translation of diagnostic and therapeutic strategies for ischemic stroke.

Key words: Middle cerebral artery occlusion-reperfusion model, Diffusion kurtosis imaging, Diffusion tensor imaging, Neurite orientation dispersion and density imaging