The use of diffusional kurtosis imaging and neurite orientation dispersion and density imaging of the brain in bipolar disorder.

BACKGROUND

Diffusional kurtosis imaging (DKI) and neurite orientation dispersion and density imaging (NODDI) are new diffusional magnetic resonance imaging (dMRI) techniques to clarify the characterization of neural tissues in the human brain. In this study, we evaluated the structural changes of the cerebrum in patients with bipolar disorder (BD) by these dMRI techniques.

METHODS

Thirty-one Japanese patients with BD (male/female: 14/17; 29 out of 31 patients were right-handed; mean age: 39.5 ± 9.3) and 28 healthy, right-handed Japanese subjects underwent 3-Tesla dMRI. We compared the dMRI metrics between the 2 groups and examined the relationships among the metrics.

LIMITATION

The majority of the participants in this study were medicated with antidepressants and antipsychotics. Further studies with drug-free participants will be needed before any conclusions can be drawn regarding microstructural changes in BD.

RESULTS

The BD patients showed significantly reduced mean kurtosis in right inferior front-occipital fasciculus and right posterior cingulate cortex (PCC), and neurite density indices in the right -PCC, compared with the controls. As for the orientation dispersion index, we detected significant decrease in the left hippocampal region of BD patients.

CONCLUSIONS

Using the new dMRI techniques, we observed disease-related alterations in the inferior front-occipital fasciculus, PCC, and hippocampal regions which play important roles in BD. These results may indicate that NODDI and DKI are useful to detect changes in the microstructural tissue organization in BD. It is anticipated that these techniques will be adopted as the mainstream methods for neuroimaging study.